OVERVIEW, CAUSES AND RISK FACTORS:
Is ADHD over-diagnosed? Under-diagnosed? Probably both -- and certainly real. ADHD affects children's school performance and their relationships with others. Parents who are wondering if their children have ADHD are often exhausted and frustrated.

Scientific studies, using advanced neuroimaging techniques of brain structure and function, show that the brains of children with ADHD are different from those of other children. These children handle neurotransmitters (including dopamine, serotonin, and adrenalin) differently from their peers.

ADHD is often genetic. Whatever the specific cause may be, it seems to be set in motion very early in life as the brain is developing. Other problems, such as depression, sleep deprivation, specific learning disabilities, tic disorders, and oppositional/aggressive behavior problems, may be confused with or appear along with ADHD. Every child suspected of having ADHD deserves a careful evaluation to sort out exactly what is contributing to his concerning behaviors.

Attention Deficit Disorder (ADD) is the most commonly diagnosed behavioral disorder of childhood, affecting an estimated 3 - 5% of school aged children. It is diagnosed much more often in boys than in girls.

Most children with ADHD also have at least one other developmental or behavioral problem. Every evaluation should include a search for possible additional conditions, including conduct disorder, oppositional defiant disorder, mood disorders, depression, anxiety, and learning disabilities.

OVERVIEW, CAUSES AND RISK FACTORS:
IAllergy is caused by an oversensitive immune system, which leads to a misdirected immune response. The immune system normally protects the body against harmful substances, such as bacteria and viruses. In contrast, an allergic reaction is when the immune system reacts to substances (allergens) that are generally harmless and in most people do not cause an immune response.

In a person with allergies, the first exposure to the allergen triggers the immune system to recognize the substance. Any exposure after that will usually result in symptoms.

When an allergen enters the body of a person with a sensitized immune system, histamine and other chemicals are released by certain cells. This causes itching, swelling, mucus production, muscle spasms, hives, rashes, and other symptoms.

Symptoms vary in severity from person to person. Most people have symptoms that cause discomfort without being life-threatening. A few people have life-threatening reactions (called anaphylaxis)

The part of the body contacted by the allergen will, in part, affect the symptoms. For example, allergens that are inhaled often cause nasal congestion, itchy nose and throat, mucus production, cough, or wheezing. A food allergen can cause nausea, vomiting, abdominal pain, cramping, diarrhea, or a severe, life-threatening reaction. Allergies to plants often cause skin rash. Drug allergies usually involve the whole body.

Some disorders may be associated with allergies. These include eczema and asthma, among others.

Common allergens include those that contact the skin, breathing passages, or the surface of the eye (such as pollen; see also allergy to mold, dander, dust). Food allergies and drug allergies are common. Allergic reactions can be caused by insect bites, jewelry, cosmetics, and almost any substance that contacts the body.

Some people have allergic-type reactions to hot or cold temperatures, sunlight, or other physical stimuli. In some persons, friction (rubbing or vigorously stroking the skin) will cause symptoms. (See also atopic dermatitis and contact dermatitis.)

Allergies are relatively common. Both hereditary and environmental factors have been found to play a role.

OVERVIEW, CAUSES AND RISK FACTORS:
The cause of Alzheimer's disease (AD) is not known, but it is not a part of normal aging. Prior theories regarding the accumulation of aluminum, lead, mercury, and other substances in the brain have been disproved.

A diagnosis of AD is made based on characteristic symptoms and by excluding other causes of dementia. It can be confirmed by microscopic examination of a sample of brain tissue after death.

Brain tissue shows "neurofibrillary tangles" (twisted fragments of protein within nerve cells that clog up the cell), "neuritic plaques" (abnormal clusters of dead and dying nerve cells, other brain cells, and protein), and "senile plaques" (areas where products of dying nerve cells have accumulated around protein). Although these changes occur to some extent in all brains with age, there are many more of them in the brains of people with AD.

The destruction of nerve cells (neurons) leads to a decrease in neurotransmitters (substances secreted by a neuron to send a message to another neuron). The correct balance of neurotransmitters is critical to the brain. Three neurotransmitters commonly affected by AD are acetylcholine, serotonin, and norepinephrine -- with acetylcholine being the most affected.

By causing both structural and chemical problems in the brain, AD appears to disconnect areas of the brain that normally work together

As many as 4 million Americans currently suffer from AD. The most important risk factors for dementia are old age and a family history of dementia. The older you get, the greater your risk of developing AD.

About 10 percent of all people over 70 have significant memory problems and about half of those are due to AD. The number of people with AD doubles each decade past age 70. Having a close blood relative who developed AD increases risk. Because women usually live longer than men, they are more likely to develop AD.

There are two types of AD -- early onset and late onset. In early onset AD, symptoms first appear before age 60. Some early onset disease runs in families and involves autosomal dominant, inherited mutations that may be the cause of the disease. So far, three early onset genes have been identified. Early onset AD is less common, resulting in about 5-10% of cases.

Late onset AD, the most common form of the disease, develops in people 60 and older and is thought to be less likely to occur in families. Late onset AD may run in some families, but the role of genes is less direct and definitive. These genes may not cause the problem itself, but simply increase the likelihood of formation of plaques and tangles or other AD-related pathologies in the brain.

OVERVIEW, CAUSES AND RISK FACTORS:

OVERVIEW, CAUSES AND RISK FACTORS:
Asthma is a disease in which inflammation of the airways causes airflow into and out of the lungs to be restricted. When an asthma attack occurs, the muscles of the bronchial tree become tight and the lining of the air passages swells, reducing airflow and producing the characteristic wheezing sound. Mucus production is increased.

Most people with asthma have periodic wheezing attacks separated by symptom-free periods. Some asthmatics have chronic shortness of breath with episodes of increased shortness of breath. Other asthmatics may have cough as their predominant symptom. Asthma attacks can last minutes to days, and can become dangerous if the airflow becomes severely restricted.

In sensitive individuals, asthma symptoms can be triggered by inhaled allergens (allergy triggers), such as pet dander, dust mites, cockroach allergens, molds, or pollens. Asthma symptoms can also be triggered by respiratory infections, exercise, cold air, tobacco smoke and other pollutants, stress, food, or drug allergies. Aspirin and other non-steroidal anti-inflammatory medications (NSAIDS) provoke asthma in some patients.

Asthma is found in 3-5% of adults and 7-10% of children. Half of the people with asthma develop it before age 10, and most develop it before age 30. Asthma symptoms can decrease over time, especially in children.

Many people with asthma have an individual and/or family history of allergies, such as hay fever (allergic rhinitis) or eczema. Others have no history of allergies or evidence of allergic problems.

Arthritis can occur in males and females of all ages. About 37 million people in America have arthritis of some kind, which is almost 1 out of every 7 people. In people over 55 years of age, women are more likely to suffer from osteoarthritis. Other risk factors for osteoarthritis are obesity, a history of trauma, and various genetic and metabolic diseases.

OVERVIEW, CAUSES AND RISK FACTORS:

OVERVIEW, CAUSES AND RISK FACTORS:
There are several different types of breast cancer. Ductal carcinoma begins in the cells lining the ducts that bring milk to the nipple and accounts for more than three-fourths of breast cancer.

Lobular carcinoma begins in the milk-secreting glands of the breast but is otherwise fairly similar in its behavior to ductal carcinoma. Other varieties of breast cancer can arise from the skin, fat, connective tissues, and other cells present in the breast.

Risk factors for breast cancer include :

• Age and Gender: As with most cancers, age is a significant factor. In fact, 77% of new cases and 84% of breast cancer deaths occur in women aged 50 and older. More than 80% of breast cancer cases occur in women over 50. Less than 1% of breast cancers occur in men. The risk of breast cancer is clearly related to hormonal influences, but how these affect the disease and particularly types of the disease is not yet clear.
• Genetic Factors and Family History of Breast Cancer: Some families appear to have a genetic tendency for breast cancer. Two variant genes have been found that appear to account for this: BRCA1 and BRCA2. The genes p53 and BARD1 also appear to be important. Researchers have identified some other defective genes that may cause breast cancer, including BRCA3 and Noey2 (which is a disease inherited only from the father's side of the family).
  These facts suggest that breast cancer is caused by the growth of genetically damaged cells. Such genetic damage is known to gradually accumulate in the cells of the body over time. Women carrying mutated BRCA1 and/or BRCA2 genes have a "head start" in this process.
  Hormonal influences are important because they encourage cell growth. High levels of hormones during a woman's reproductive years, especially when they are not interrupted by the hormonal changes of pregnancy, appear to increase the chances that genetically damaged cells will grow and cause cancer.
• Early Menstruation and Late Menopause: Women who started menstrual periods early (before age 12) or went through menopause late (after age 55) are at higher risk. Also, women who have never had children or who had them only after the age of 30 have an increased risk.
• Oral Contraceptives (birth control pills): Birth control pills may slightly increase the risk for breast cancer, depending on age, length of use, and other factors. No one knows how long the effects of the pill last after stopping it.
• Hormone Replacement Therapy: Use of HRT for more than 5 years has been shown to slightly increase the risk of breast cancer and risk increases with longer use.
• Physical Characteristics: Obesity is controversial as a risk factor. Some studies report obesity as a risk of breast cancer, possibly associated with higher levels of estrogen production in obese women.
• Alcohol Consumption: Excessive alcohol use (more than 1-2 drinks a day) has been associated with an increased risk of breast cancer.
• Chemicals: Some studies have pointed to exposure to estrogen-like chemicals that are found in pesticides and other industrial products as a possible increased risk of breast cancer.
• DES: Women who took diethylstilbestrol (DES) to prevent miscarriage may have an increased risk of breast cancer.
• Radiation: People exposed to radiation, particularly during childhood may face an increased risk for breast cancer in adulthood. Especially at risk are those that received chest irradiation for prior cancers.
• Additional Risk Factors: Some studies show previous breast, uterine, ovarian, colon cancer, and a strong history of cancer in the family may increase the risk for breast cancer.

The Gail Model is a simple breast cancer risk assessment tool that is available online and takes into account the most important risk factors.

OVERVIEW, CAUSES AND RISK FACTORS:
There are at least 200 different kinds of cancers. They can develop in almost any organ, fluid, or tissue. Some cancers affect blood cells, some affect skin; others affect bone, muscle, or nerve tissue.
In general, cancer appears to be caused by abnormal regulation of cell growth. Typically, the growth of cells in the body is strictly controlled -- new cells are made as needed to replace older ones or to perform needed functions. Cells die when they become damaged and/or are no longer needed. If the balance of cell growth and death is disturbed, cancer may occur.
Problems in the regulation of cell growth can be caused by abnormalities of the immune system, which normally would detect and stop aberrant growth. Other potential causes of cancer include the following..

• Radiation
• Sunlight
• Tobacco
• Certain viruses
• Benzene
• Certain poisonous mushrooms and aflatoxins (a poison produced by organisms that can grow on peanut plants)

The three most common cancers in men in the U.S. are prostate cancer, lung cancer, and colon cancer. In women here, the three most frequently occurring cancers are breast cancer, lung cancer, and colon cancer.

The most common cause of cancer-related death is lung cancer.

Certain cancers are more common in particular geographic regions. For example, in Japan, there are many cases of gastric cancer while in the US this type of cancer is relatively rare. Dietary differences may account for the variance.

OVERVIEW, CAUSES AND RISK FACTORS:
There are over 130,000 cases of colorectal cancer diagnosed in the United States each year, and over 50,000 deaths. Colorectal cancer is the second leading cause of cancer deaths. In almost all cases, however, this disease is entirely treatable if caught early by colonoscopy.

There is no single cause for colon cancer. However, almost all colon cancers begin as benign polyps which, over a period of many years, develop into cancers.

Factors that increase the risk of colon cancer are colorectal polyps, cancer elsewhere in the body, a family history of colon cancer, and ulcerative colitis.

Patients with a history of breast cancer have a slightly increased risk of developing colon cancer. Certain genetic syndromes increase the risk of developing colon cancer in affected families.

Dietary factors that have been associated with colon cancer are a high-meat, high-fat, low-fiber diet. However, some studies found that the risk is not reduced when people switch to a high-fiber diet, so the cause of the link is not yet clear.

OVERVIEW, CAUSES AND RISK FACTORS:
Depression is generally ranked in terms of severity -- mild, moderate, or severe. The degree of your depression, which your doctor can determine, influences how you are treated.
Symptoms of depression include:

• Sleep disturbances -- usually insomnia (for example, consistently waking up very early in the morning) but may be excessive sleeping
• A dramatic change in appetite, often resulting in either weight gain or weight loss
• Fatigue and lack of energy
• Feelings of worthlessness, self-hate, and inappropriate guilt
• Extreme difficulty concentrating
• Agitation, restlessness, and irritability OR inactivity and withdrawal from usual activities
• Recurring thoughts of death or suicide
• Feelings of hopelessness and helplessness

Low self esteem is common with depression. So are sudden bursts of anger and lack of pleasure from activities that normally make you happy, including sex.

The main types of depression include:

• Major depression: five or more symptoms listed above must be present for at least 2 weeks, but tends to continue for 20 weeks. (A mood disorder is classified as minor depression if less than five depressive symptoms are present for at least 2 weeks.)
• Dysthymia: a chronic, generally milder form of depression but lasts longer -- usually as long as two years.
• A typical depression: depression accompanied by unusual symptoms, such as hallucinations (for example, hearing voices that are not really there) or delusions (irrational thoughts). Other common forms of depression include:
• Postpartum depression: many women feel somewhat down after having a baby, but true postpartum depression is rare.
• Premenstrual dysphoric disorder (PDD): depressive symptoms occur one week prior to menstruation and disappear after you menstruate.
• Seasonal affective disorder (SAD): occurs during the fall-winter season and disappears during the spring-summer season. Likely to be due to lack of sunlight.

Depression may also occur with mania (known as manic-depression or bipolar disorder). In this condition, moods cycle between mania and depression.

Depression is more common in women than men and is especially common during the teen years. Men seem to seek help for feelings of depression less often than women. Therefore, women may only have more documented cases of depression.

OVERVIEW, CAUSES AND RISK FACTORS:
To understand diabetes, it is important to first understand the normal process of food metabolism. Several things happen when food is digested : Symptoms of depression include:

• A sugar called glucose enters the bloodstream. Glucose is a source of fuel for the body.
• An organ called the pancreas makes insulin. The role of insulin is to move glucose from the bloodstream into muscle, fat, and liver cells, where it can be used as fuel

People with diabetes have high blood glucose. This is because their pancreas does not make enough insulin or their muscle, fat, and liver cells do not respond to insulin normally, or both.

There are three major types of diabetes:

• Type 1 diabetes is usually diagnosed in childhood. The body makes little or no insulin, and daily injections of insulin are required to sustain life. Without proper daily management, medical emergencies can arise.
• Type 2 diabetes is far more common than type 1 and makes up 90% or more of all cases of diabetes. It usually occurs in adulthood. Here, the pancreas does not make enough insulin to keep blood glucose levels normal, often because the body does not respond well to the insulin. Many people with type 2 diabetes do not know they have it, although it is a serious condition. Type 2 diabetes is becoming more common due to the growing number of older Americans, increasing obesity, and failure to exercise.
• Gestational diabetes is high blood glucose that develops at any time during pregnancy in a person who does not have diabetes.

Diabetes affects about 17 million Americans. There are many risk factors for diabetes, including:

• A parent, brother, or sister with diabetes
• Obesity
• Age greater than 45 years
• Some ethnic groups (particularly African-Americans and Hispanic Americans)
• Gestational diabetes or delivering a baby weighing more than 9 pounds
• High blood pressure
• High blood levels of triglycerides (a type of fat molecule)
• High blood cholesterol level

The American Diabetes Association recommends that all adults be screened for diabetes at least every three years. A person at high risk should be screened more often.

OVERVIEW, CAUSES AND RISK FACTORS:
The gallbladder is a sac located under the liver. It stores and concentrates the bile produced in the liver, which aids in the digestion of fats. Bile is released from the gallbladder in response to food, especially fats, in the upper small intestine (duodenum). Conditions which slow or obstruct the flow of bile out of the gallbladder result in gallbladder disease.
Types of gallbladder disease include:

• cholecystitis (inflammation of the gallbladder)
• cholelithiasis (gall stones)

OVERVIEW, CAUSES AND RISK FACTORS:
Most heart attacks are caused by a clot that blocks one of the coronary arteries (the blood vessels that bring blood and oxygen to the heart muscle). The clot usually forms in a coronary artery that has been previously narrowed from changes related to atherosclerosis. The atherosclerotic plaque (buildup) inside the arterial wall sometimes cracks, and this triggers the formation of a clot, also called a thrombus.

A clot in the coronary artery interrupts the flow of blood and oxygen to the heart muscle, leading to the death of heart cells in that area. The damaged heart muscle loses its ability to contract, and the remaining heart muscle needs to compensate for that weakened area.

Occasionally, sudden overwhelming stress can trigger a heart attack.

It is difficult to estimate exactly how common heart attacks are because as many as 200,000 to 300,000 people in the United States die each year before medical help is sought. It is estimated that approximately 1 million patients visit the hospital each year with a heart attack.

The risk factors for coronary artery disease and heart attack include:

• Smoking
• High blood pressure
• Too much fat in your diet
• Poor blood cholesterol levels, especially high LDL ("bad") cholesterol and low HDL ("good") cholesterol
• Diabetes
• Male gender
• Age
• Heredity

Many of the risk factors listed are related to being overweight.

Newer risk factors for coronary artery disease have been identified over the past several years, including elevated homocysteine, C-reactive protein, and fibrinogen levels. High homocysteine can be treated with folic acid supplements in the diet. Studies are still ongoing about the practical value of these new factors.

Heart attack accounts for 1 out of every 5 deaths. It is a major cause of sudden death in adults.

OVERVIEW, CAUSES AND RISK FACTORS:
The disease can be caused by:

• Infections from parasites, bacteria, or viruses (such as Hepatitis A, B, or C)
• Liver damage from alcohol, drugs, or poisonous mushrooms
• An overdose of acetaminophen (such as Tylenol), which is rare but can be deadly (more common if you drink alcohol regularly)
• Immune cells in the body attacking the liver and causing autoimmune hepatitis

Other medications that can cause damage to the liver include methyldopa (used uncommonly for high blood pressure), isoniazide for tuberculosis, seizure medications (like valproate and phenytoin), chlorpromazine, amiodarone (for irregular heart rhythm), and certain antibiotics (including trimethoprim-sulfamethoxazole and erythromycin). If you need to take any of these, your doctor will follow your liver function closely.

Liver disease can also be caused by inherited disorders such as cystic fibrosis and Wilson's disease, a condition that involves having too much copper in your body; the excess copper deposits in organs like your liver.

Hepatitis may start and resolve quickly (acute hepatitis), or cause long-term disease (chronic hepatitis). In some instances, progressive liver damage, liver failure, or even liver cancer may result.

The severity of hepatitis depends on many factors, including the cause of the liver damage and any underlying illnesses you have. Hepatitis A, for example, is generally short-lived, not leading to chronic liver problems.

Common risk factors include:

• Intravenous drug use
• Acetominophen overdose -- the dose needed to cause damage is close to the effective dose, so be careful to take it only as directed; DO NOT use if you already have underlying liver damage
• Risky sexual behaviors (like having multiple sexual partners and unprotected intercourse)
• Eating contaminated foods
• Travel to an endemic area, like Asia, Africa, or South or Central America
• Living in a nursing home or rehabilitation center
• Family member who recently had hepatitis A
• Alcohol use
• Organ transplant recipient
• AIDS
• Blood transfusion received prior to 1990 (before hepatitis C blood test was available)
• Newborns of mothers with hepatitis B or C (can be transmitted during delivery)
• Healthcare workers, including dentists and dental hygienists, because of blood contact
• Receiving a tatoo

Heart attack accounts for 1 out of every 5 deaths. It is a major cause of sudden death in adults.

OVERVIEW, CAUSES AND RISK FACTORS:

AIDS (Acquired Immune Deficiency Syndrome) is the final and most serious stage of HIV disease, which causes severe damage to the immune system.

The Centers for Disease Control has defined AIDS as beginning when a person with HIV infection has a CD4 cell (also called "t-cell", a type of immune cell) count below 200. It is also defined by numerous opportunistic infections and cancers that occur in the presence of HIV infection.

OVERVIEW, CAUSES AND RISK FACTORS:
AIDS is the fifth leading cause of death among persons between ages 25 and 44 in the United States. About 47 million people worldwide have been infected with HIV since the start of the epidemic.

The Human Immunodeficiency Virus (HIV) causes AIDS. The virus attacks the immune system and leaves the body vulnerable to a variety of life-threatening illnesses and cancers.

Common bacteria, yeast, parasites, and viruses that ordinarily do not cause serious disease in people with fully functional immune systems can cause fatal illnesses in people with AIDS.

HIV has been found in saliva, tears, nervous system tissue, blood, semen (including pre-seminal fluid, or "pre-cum"), vaginal fluid, and breast milk. However, only blood, semen, vaginal secretions, and breast milk have been proven to transmit infection to others.

Transmission of the virus occurs:

1. through sexual contact -- including oral, vaginal, and anal sex
2. through blood -- via blood transfusions (now extremely rare in the U.S) or needle sharing
3. from mother to child -- a pregnant woman can passively transmit the virus to her fetus, or a nursing mother can transmit it to her baby

Other transmission methods are rare and include accidental needle injury, artificial insemination with donated semen, and through a donated organ.

HIV infection is not spread by casual contact (such as hugging and touching), by touching dishes, doorknobs, or toilet seats previously touched by a person infected with the virus, during participation in sports, or by mosquitoes.

It is not transmitted to a person who DONTATES blood or organs in the U.S. because hospitals do not re-use syringes and sterilize all devices involved in such procedures.

However, HIV can be transmitted to the person RECEIVING blood or organs from an infected donor. This is why blood banks and organ donor programs screen donors, blood, and tissues thoroughly.

Those at highest risk include homosexual or bisexual men engaging in unprotected sex, intravenous drug users who share needles, the sexual partners of those who participate in high-risk activities, infants born to mothers with HIV, and people who received blood transfusions or clotting products between 1977 and 1985 (prior to standard screening for the virus in the blood).

AIDS begins with HIV infection. People infected with HIV may have no symptoms for ten years or longer, but they can still transmit the infection to others during this symptom-free period. Meanwhile, their immune system gradually weakens until they develop AIDS.

Acute HIV infection progresses over time to asymptomatic HIV infection and then to early symptomatic HIV infection. Later, it progresses to AIDS (very advanced HIV infection with T-cell count below 200).

Most individuals infected with HIV will progress to AIDS, if not treated. However, there is a tiny group of patients who develop AIDS very slowly or never at all. These patients are called non-progressors and many seem to have a genetic difference which prevents the virus from attaching to certain immune receptors.

Hypertension means high blood pressure. This generally means:

• systolic blood pressure is consistently over 140 (systolic is the "top" number of your blood pressure measurement, which represents the pressure generated when the heart beats)
• diastolic blood pressure is consistently over 90 (diastolic is the "bottom" number of your blood pressure measurement, which represents the pressure in the vessels when the heart is at rest)

Either or both of these numbers may be too high.

Pre-hypertension is when your systolic blood pressure is between 120 and 139 or your diastolic blood pressure is between 90 and 99 on multiple readings. If you have pre-hypertension, you are likely to develop high blood pressure at some point. Therefore, your doctor will recommend lifestyle changes to bring your blood pressure down to normal range.

OVERVIEW, CAUSES AND RISK FACTORS:
Blood pressure is determined by the amount of blood pumped by the heart, and the size and condition of the arteries. Many other factors can affect blood pressure, including volume of water in the body; salt content of the body; condition of the kidneys, nervous system, or blood vessels; and levels of various hormones in the body.

"Essential" hypertension has no identifiable cause. It may have genetic factors and environmental factors, such as salt intake or others. Essential hypertension comprises over 95% of all high blood pressure.

"Secondary" hypertension is high blood

• pressure caused by another disorder. This may include:
• adrenal gland tumors
• Cushing's syndrome
• kidney disorders
• glomerulonephritis (inflammation of kidneys)
• renal vascular obstruction or narrowing
• renal failure
• use of medications, drugs, or other chemicals
• oral contraceptives
• hemolytic-uremic syndrome
• Henoch-Schonlein purpura
• periarteritis nodosa
• radiation enteritis
• retroperitoneal fibrosis
• Wilms' tumor
• other disorders

Other transmission methods are rare and include accidental needle injury, artificial insemination with donated semen, and through a donated organ.

Lung cancer is a malignant tumor of the lungs. There are many types of lung cancer, but most can be categorized into two basic types, "small cell" and "non-small cell." Small cell lung cancer is generally faster growing than non-small cell, but more likely to respond to chemotherapy.

Small cell cancer is divided into "limited stage" (generally cancer confined to the chest) and "extensive stage" (cancer that has spread outside the chest).

The traditional staging system, which divides cancer into stages I through IV, is not generally applicable to small cell lung cancer.

OVERVIEW, CAUSES AND RISK FACTORS:
Most lung cancers are caused by cigarette smoking. The more cigarettes you smoke per day and the earlier you started smoking, the greater the risk of lung cancer.

Second-hand smoke increases the risk. Government surveys show that as many as 3,000 people each year develop lung cancer from second-hand smoke. High levels of pollution, radiation, and asbestos exposure may also increase risk.

Lung cancer begins in cells that line the airways and often invade adjacent tissues or spread elsewhere in the body before symptoms are noticed.

About 20% of all lung cancer cases are small cell lung cancer, meaning about 30,000 patients each year are diagnosed with this disease.

Menopause is the transition period in a woman's life when the ovaries stop producing eggs, the body decreases the production of the female hormones estrogen and progesterone, and menstrual activity diminishes and eventually ceases.

OVERVIEW, CAUSES AND RISK FACTORS:
Menopause is a natural event which normally occurs between the ages of 45 and 55, beginning, on average, at age 51.

During menopause, ovulation (egg production) stops and menstruation becomes less frequent, eventually stopping altogether. Once menopause is complete (called postmenopause), you can no longer become pregnant.

The symptoms of menopause are caused by changes in estrogen and progesterone levels. As the ovaries become less functional, they produce less of these hormones and the body responds accordingly. The specific symptoms you experience and how significant (mild, moderate, or severe) varies from woman to woman.

In some women, menstrual flow comes to a sudden halt. More commonly, however, it tapers off, both in amount and duration of flow. During this time, often called perimenopause, your menstrual periods generally become either more closely or more widely spaced. This irregularity may last for 1 to 3 years before menstruation finally ends completely.

A gradual decrease of estrogen generally allows your body to slowly adjust to the hormonal changes. When estrogen drops suddenly, as is seen when the ovaries are removed surgically (called surgical menopause), symptoms can be more severe.

Migraine headaches are a type of headache that some people get repeatedly over time. Migraines are different from other headaches because they occur with symptoms such as nausea, vomiting, or sensitivity to light.

Some people who get migraines have warning symptoms, called an aura, before the actual headache begins. Most people, however, do not have such warning symptoms.

OVERVIEW, CAUSES AND RISK FACTORS:
A lot of people get migraines -- about 6 out of 100. The headaches tend to start between the ages of 10 and 46, may run in families, and occur in women more often than men.

Migraines are classified as either "common" or "classic". Common migraines do not have any warning symptoms, while classic migraines do have a warning (the aura). Most migraine patients have the common type.

The exact cause of migraine is not known. Migraine headaches are related to problems with blood flow through parts of the brain. At the start of a migraine, blood vessels in certain areas of the brain constrict (narrow), leading to symptoms like visual disturbances, difficulty speaking, weakness, or numbness. Minutes to hours later, the blood vessels dilate (enlarge), leading to increased blood flow in the brain and a bad headache.

Why these changes in the blood vessels (and blood flow) occur in the brain is not understood. Certain triggers, however, make it more likely for you to get migraines:

• Allergic reactions
• Bright lights, loud noises, and certain odors or perfumes
• Physical or emotional stress
• Changes in sleep patterns
• Smoking or exposure to smoke
• Skipping meals
• Alcohol or caffeine
• Hormonal fluctuations (related to menstrual cycles or use of birth control pills, for example)
• Tension headaches
• Certain foods like those containing the amino acid tyramine (red wine, aged cheese, smoked fish, chicken livers, figs, and some beans), chocolate, nuts, peanut butter, some fruits (avocado, banana, and citrus), monosodium glutamate (a food additive commonly called MSG), onions, dairy products, meats containg nitrates (like bacon, hot dogs, and salami), and fermented or pickled foods

OVERVIEW, CAUSES AND RISK FACTORS:
Some people who get migraines have warning symptoms, called an aura, before the actual headache begins. Most people, however, do not have such warning symptoms.

Osteoporosis occurs when the body fails to form enough new bone, or when too much old bone is reabsorbed by the body, or both.

Calcium and phosphate are two minerals that are essential for normal bone formation. Throughout youth, the body uses these minerals to produce bones. If calcium intake is not sufficient, or if the body does not absorb enough calcium from the diet, bone production and bone tissues may suffer.

As people age, calcium and phosphate may be reabsorbed back into the body from the bones, which makes the bone tissue weaker. Both situations can result in brittle, fragile bones that are subject to fractures, even in the absence of trauma.

Usually, the loss occurs gradually over years. Many times, a person will sustain a fracture before becoming aware that the disease is present. By the time this occurs, the disease is in its advanced stages and the damage is profound.

The leading causes are a drop in estrogen in women at the time of menopause, and a drop in testosterone in men. Women, especially those over the age of 50, get osteoporosis more often than men.

Other causes include corticosteroid excess from Cushing's syndrome, hyperthyroidism, hyperparathyroidism, being confined to a bed, and bone cancers.

Researchers estimate that about 20% of American women over the age of 50 have osteoporosis. In addition, another 30% of them have osteopenia, which is abnormally low bone density that may eventually deteriorate into osteoporosis, if not treated.

About half of all women over the age of 50 will suffer a fracture of the hip, wrist, or vertebra.

Women who are white, especially those with a family history of osteoporosis, have a greater risk of developing osteoporosis. Other risk factors include smoking, eating disorders, low body weight, low amount of calcium in the diet, heavy alcohol consumption, early menopause, absence of menstrual periods (amenorrhea), and use of certain medications, such as steroids and anticonvulsants.

Pneumonia is an inflammation of the lungs caused by an infection. Many different organisms can cause it, including bacteria, viruses, and fungi.

Pneumonia is a common illness that affects millions of people each year in the United States.

Pneumonia can range from very mild to very severe, even fatal. The severity depends on the type of organism causing pneumonia as well as your age and underlying health.

OVERVIEW, CAUSES AND RISK FACTORS:
Bacterial pneumonias tend to be the most serious and, in adults, the most common cause, especially Streptococcus pneumoniae (pneumococcus).

Respiratory viruses are the most common causes of pneumonia in young children, peaking between the ages of 2 and 3. By school age, the bacterium Mycoplasma pneumoniae becomes more common.

In some people, particularly the elderly and those who are debilitated, bacterial pneumonia may follow influenza or even a common cold.

Many people contract pneumonia while staying in a hospital for other conditions. This tends to be more serious because the patient's immune system is often impaired due to the condition that initially required treatment. In addition, there is a greater possibility of infection with bacteria that are resistant to antibiotics.

OVERVIEW, CAUSES AND RISK FACTORS:
The cause of prostate cancer is unknown, although some studies have shown a relationship between high dietary fat intake and increased testosterone levels. When testosterone levels are lowered either by surgical removal of the testicles (castration, orchiectomy) or by medication, prostate cancer can regress. There is no known association with benign prostatic hyperplasia (BPH).

Prostate cancer is the third most common cause of death from cancer in men of all ages and is the most common cause of death from cancer in men over 75 years old. Prostate cancer is rarely found in men younger than 40.

Prostate cancer is the third most common cause of death from cancer in men of all ages and is the most common cause of death from cancer in men over 75 years old. Prostate cancer is rarely found in men younger than 40.

Men at higher risk include black men older than 60, farmers, tire workers, painters, and men exposed to cadmium. The lowest incidence occurs in Japanese men and vegetarians.

Prostate cancers are classified or staged based on their aggressiveness and how different they are from the surrounding prostate tissue. There are several different ways to stage tumors; one of the more common is the A-B-C-D staging system (also known as the Whitmore-Jewett system).

A: tumor not palpable (unable to be felt on physical examination). Usually detected by accident after prostate surgery done for other reasons.
B: tumor is confined to the prostate and usually detected by physical examination or PSA testing.
C: extension of tumor beyond the prostate capsule without spread to lymph nodes.
D: cancer has spread (metastasized) to regional lymph nodes or other parts of the body (bone and lungs for example).

Severe Acute Respiratory Syndrome (SARS) is a serious form of pneumonia, resulting in acute respiratory distress and sometimes death. It is a dramatic example of how quickly world travel can spread a disease. It is also an example of how quickly a networked health system can respond to an emerging threat.

This contagious respiratory infection was first described on February 26, 2003. SARS was identified as a new disease by World Health Organization (WHO) physician Dr. Carlo Urbani. He diagnosed it in a 48-year-old businessman who had traveled from the Guangdong province of China, through Hong Kong, to Hanoi, Vietnam. The businessman died from the illness. Dr. Urbani subsequently died from SARS on March 29, 2003 at the age of 46.

In the meantime, SARS was spreading, and within 6 weeks of its discovery, it had infected thousands of people around the world, including people in Asia, Australia, Europe, Africa, and North and South America. Schools had closed throughout Hong Kong and Singapore. National economies were affected.

The WHO had identified SARS as a global health threat, and issued an unprecedented travel advisory. Daily WHO updates tracked the spread of SARS seven days a week. It wasn't clear whether SARS would become a global pandemic, or would settle into a less aggressive pattern.

The rapid, global public health response helped to stem the spread of the virus, and by June 2003, the epidemic had subsided to the degree that on June 7 the WHO backed off from its daily reports. Nevertheless, even as the number of new cases dwindled, and travel advisories began to be lifted, the sober truth remained: every new case had the potential to spark another outbreak. SARS appears to be here to stay, and to have changed the way that the world responds to infectious diseases in the era of widespread international travel.

OVERVIEW, CAUSES AND RISK FACTORS:
SARS is caused by a new member of the coronavirus family (the same family that can cause the common cold). The discovery of these viral particles represents some of the fastest identification of a new organism in history.

SARS is clearly spread by droplet contact. When someone with SARS coughs or sneezes, infected droplets are sprayed into the air. Like other coronaviruses, the SARS virus may live on hands, tissues, and other surfaces for up to 6 hours in these droplets and up to 3 hours after the droplets have dried.

While droplet transmission through close contact was responsible for most of the early cases of SARS, evidence began to mount that SARS might also spread by hands and other objects the droplets had touched. Airborne transmission was a real possibility in some cases. Live virus had even been found in the stool of people with SARS, where it has been shown to live for up to four days. And the virus may be able to live for months or years when the temperature is below freezing.

With other coronaviruses, re-infection is common. Preliminary reports suggest that this may also be the case with SARS.

Preliminary estimates are that the incubation period is usually between two and ten days, although there have been documented cases where the onset of illness was considerably faster or slower. People with active symptoms of illness are clearly contagious, but it is not known how long contagiousness may begin before symptoms appear or how long contagiousness might linger after the symptoms have disappeared.

Reports of possible relapse in patients who have been treated and released from the hospital raise concerns about the length of time individuals can harbor the virus.

SA stroke is an interruption of the blood supply to any part of the brain, resulting in damaged brain tissue.

OVERVIEW, CAUSES AND RISK FACTORS:
Stroke accounts for 1 out of every 15 deaths in the United States. It is the 3rd leading cause of death in most developed countries, and the leading cause of disability in adults. The risk doubles with each decade after age 35.

If the flow of blood in an artery supplying the brain is interrupted for longer than a few seconds, brain cells can die, causing permanent damage. An interruption can be caused by either blood clots or bleeding in the brain.

Most strokes are due to blood clots that block blood flow. Bleeding into the brain occurs if a blood vessel ruptures or if there is a significant injury.

BLOOD CLOTS

A common cause of stroke is atherosclerosis. (See stroke secondary to atherosclerosis.) Fatty deposits and blood platelets collect on the wall of the arteries, forming plaques. Over time, the plaques slowly begin to block the flow of blood. The plaque itself may block the artery enough to cause a stroke.

Often, the plaque causes the blood to flow abnormally, which leads to a blood clot. A clot can stay at the site of narrowing and prevent blood flow to all of the smaller arteries it supplies. (This type of clot, which doesn't travel, is called a thrombus.) In other cases, the clot can travel and wedge into a smaller vessel. (A clot that travels is called an embolism.)

Strokes caused by embolism are most commonly caused by heart disorders. An embolism may originate in a major blood vessel as it branches off the heart. A clot can also form elsewhere in the body for any number of reasons, and then travel to the brain, causing a stroke.

BLEEDING IN THE BRAIN

A second major cause of stroke is bleeding in the brain (hemorrhagic stroke). This can occur when small blood vessels in the brain become weak and burst. Some people have defects in the blood vessels of the brain that make this more likely. The flow of blood after the blood vessel ruptures damages brain cells.

STROKE RISKS

Having high blood pressure is the number one reason that you might have a stroke. The risk of stroke is also increased by age, family history of stroke, smoking, diabetes, high cholesterol, and heart disease.

Certain medications promote clot formation and may increase your chances for a stroke. One example is birth control pills, especially if a woman taking them also smokes and is older than 35.

Women have a risk of stroke during pregnancy and the weeks immediately after pregnancy. Overall, however, more men have strokes than women.

Cocaine use, alcohol abuse, head injury and bleeding disorders increase the risk of bleeding into the brain.

A urinary tract infection, or UTI, is an infection that can happen anywhere along the urinary tract -- the kidneys, the ureters (the tubes that take urine from each kidney to the bladder), the bladder, or the urethra (the tube that empties urine from the bladder to the outside). Most commonly, infections affect the lower urinary tract (bladder and urethra), which is called cystitis.

OVERVIEW, CAUSES AND RISK FACTORS:
Cystitis, a very common condition, is usually caused by a bacteria from the anus entering the urethra and then the bladder. This leads to inflammation and infection in the lower urinary tract.

Certain people are more likely to get UTIs. For example, women tend to get them more often because their urethra is shorter and closer to the anus. Elderly people (especially those in nursing homes) and people with diabetes also get more UTIs.

In addition, the following risk factors increase the chances of getting a UTI:

• Pregnancy and menopause
• Kidney Stones
• Sexual intercourse, especially if you have multiple partners, and using a diaphragm for birth control
• Enlarged prostate or inflammation of the prostate
• Narrowing of the urethra
• Immobility (for example, during recovery from a hip fracture)
• Inadequate fluid intake
• Bowel incontinence
• Catheterization (for example, people paralyzed from the waist down often require a catheter to remove urine since the bladder muscle does not function properly

Some children develop urinary tract infections. In boys the peak age is before the first birthday. Urinary tract infections are much more common among uncircumcised boys. In girls, the peak age for first infections is 3 years, overlapping with the toilet training period.

Cystitis in children can be promoted by abnormalities in the urinary tract. Therefore, children with cystitis
(especially those under age 5) deserve special follow-up to prevent later kidney damage.