Pneumonia

Description

Alternative Names

Risk Factors

Community-acquired pneumonia (CAP) is the most common type and develops outside of the hospital. Each year between two and four million people in the US develop CAP, and 600,000 people are hospitalized as a result. The elderly (who tend to have diminished cough and gag reflexes and faltering immune systems) and infants and young children (who have immature immune systems and small airways) are at greater risk than are young and middle-aged adults.

General Risk Factors for Hospital-Acquired (Nosocomial) Pneumonia

Pneumonia that is contracted in the hospital is called nosocomial pneumonia and affects an estimated five to 10 out of every 1,000 hospitalized patients every year. People who are hospitalized have a higher risk for developing pneumonia than those who are not.

Certain individuals, such as the elderly, the very young, and those with chronic or severe medical conditions, are of course at higher risk.

In addition, the following conditions within the hospital put patients at higher risk:

• Surgery, particularly in people over the age of 80. Among the surgical procedures that pose a particular risk are splenectomy (removal of the spleen), abdominal aortic aneurysm repair, or operations that impair coughing.
• Being in the intensive care unit (particularly newborns or patients on mechanical ventilators). In one study, 10% of ventilated patients in the ICU developed pneumonia. Ventilated patients who lie flat on their backs are at particular risk for aspiration pneumonia; raising the patient up may reduce this risk.
• Sedation is also a risk factor for patients who are hospitalized.

Hospitalized patients are particularly vulnerable to gram-negative bacteria and staphylococci, which can be very dangerous, particularly in people who are already ill.

Medical Conditions that Pose Risks for Pneumonia

Chronic Lung Disease. Chronic obstructive lung diseases, including chronic bronchitis and emphysema, affect 15 million people in the US. This condition is a major risk factors for pneumonia.

People With Compromised Immune Systems. People with impaired immune systems are extremely susceptible to pneumonia. In addition to AIDS, other conditions that compromise the immune system include organ transplantation, chemotherapy, and cancers, especially leukemia and Hodgkin's disease. Patients who are on corticosteroids or other medications that suppress the immune system are also prone to infection.

Gastroesophageal Reflux Disease. Gastroesophageal reflux disease (GERD) is a condition in which acids from the stomach move up into the esophagus (an action called reflux). Current studies indicate an association between GERD and various problems that occur in the sinuses, ears, nasal passages, and airways of the lung. People with GERD also appear to have an above-average risk for chronic bronchitis, chronic sinusitis, emphysema, pulmonary fibrosis (lung scarring), and recurrent pneumonia. If a person inhales fluid from the esophagus (aspirates) into the lungs, serious pneumonia can occur. GERD may contribute to these conditions by triggering inflammation in these upper passages. It is not yet known whether treatment of GERD would also reduce the risk for these respiratory conditions.

Factors Associated with a Higher Risk in Healthy Adults

Dormitory or Barrack Conditions. Recruits on military bases and college students are at higher than average risk for Mycoplasma pneumonia, which is usually mild. These groups are at lower risk, however, for more serious types of pneumonia.

Smoke and Environmental Pollutants. The risk for pneumonia in smokers of more than a pack a day is three times that of nonsmokers. Those who are chronically exposed to cigarette smoke, which can injure airways and damage the cilia, are also at risk. Quitting smoking reduces the risk of dying from pneumonia to normal, but the full benefit takes 10 years to be realized. Toxic fumes, industrial smoke, and other air pollutants may also damage cilia function, which is a defense again bacteria in the lungs.

Drugs and Alcohol. Alcohol or drug abuse is strongly associated with pneumonia. These substances act as sedatives and can diminish the reflexes that trigger coughing and sneezing. Alcohol also interferes with the actions of macrophages, the white blood cells that destroy bacteria and other microbes. Intravenous drug abusers are at risk for pneumonia from infections that originate at the injection site and spread through the blood stream to the lungs.

Specific Risk Factors for Recurrent Pneumonia in Children

Certain children have a higher than normal risk for pneumonia and its recurrence. Conditions that predispose infants and small children to pneumonia include the following:

• Impaired immune system.
• Gastroesophageal reflux disorder.
• Inborn lung or heart defects.
• Abnormalities in muscle coordination in the mouth and throat.
• Asthma.
• Certain genetic disorders. They include sickle-cell disease, cystic fibrosis (which causes mucus abnormalities), and Kartagener's syndrome (which results in malfunctioning cilia, the hair-like cells lining the airways).