Community-acquired pneumonia risk factors

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Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.D. [2]; Philip Marcus, M.D., M.P.H.[3]; Chetan Lokhande, M.B.B.S [4]

Overview

The risk factors for pneumonia include: smoking, age, immunosuppression, exposure to chemicals, underlying lung disease, and exposure to chemicals.

Risk Factors

Obstruction

• Airway obstruction may cause fluid accumulation in the lungs and result in CAP if the fluids become infected.

• One cause of obstruction, especially in young children, is inhalation of a foreign object such as a marble or toy. The object is lodged in the small airways and pneumonia can form in the trapped areas of lung.

• Another cause of obstruction is lung cancer, which can grow into the airways blocking the flow of air.

Lung Disease

• Smoking, and diseases such as emphysema, result in more frequent and severe bouts of CAP.

• In children, recurrent episodes of CAP may be the first clue to diseases such as cystic fibrosis or pulmonary sequestration.

• Hypoxemia

• Pulmonary edema

• Chronic obstructive pulmonary disease (COPD)

• Previous episode of pneumonia or chronic bronchitis

Immune Problems

• People who have immune system problems are more likely to get CAP.

• Risk factors for increased mortality from community acquired pneumonia are active malignancy, immunosuppression, neurological disease, congestive heart failure, coronary artery disease, and diabetes mellitus.

• People who have AIDS are much more likely to develop CAP. Pneumonia could be the first manifestation of an underlying undiagnosed HIV. It is thus recommended by the Center for Disease Control (CDC) that all patients aged 13 to 64 in a medical setting regardless of known risk factors be screened for HIV. The American College of Physicians and HIV Medicine Association recommends expanding screening for HIV from age 13 to 75 , .

• Other immune problems range from severe immune deficiencies of childhood such as Wiskott-Aldrich syndrome to less severe deficiencies such as common variable immunodeficiency.

• Elderly people are affected with increased incidence and severity of community acquired pneumonia. It is the fifth most common cause of death among individuals who are > 65 years of age, and fourth in individuals who are 85 years or older. The clinical picture in elderly could be subtle and could present only as delirium without any fever, cough or sputum. Therefore, a high index of suspicion should be kept in these groups of people.

• Immotile cilia syndrome

• Kartagener's syndrome (ciliary dysfunction, situs inversus, sinusitis, bronchiectasis)
• Young's syndrome (azoospermia, sinusitis, pneumonia)

Other Risk factors

A few other conditions can lead to pneumonia due to altered normal mechanism of lung defense.

• Dysphagia due to esophageal lesions and motility problems

• HIV infection (especially for pneumococcal pneumonia)

Drugs

Acid suppressing drugs

• Usage of H2 blockers, proton pump inhibitors, and antacids may increase the pH and hence as a result may increase the risk of pneumonia.

• A similiar study showed increase risk of pneumonia after starting PPI especially 48 hrs ago.

• Several other conditions were also associated with usage of PPI whcih would lead us to believe that there may be some confounding factor.

Antipsychotic drugs

• A case control study has shown a significant correlation between using antipsychotic drugs and community acquired pneumonia. A 60 percent increase in the rate of pneumonia can be seen in elderly patients on anti-psychotic medications.

• Atypical antipsychotic was associated with an increases risk of community acquired pneumonia.

ACE inhibitors

• A randomized trial has shown that ACE inhibitors when used reduces the risk of pneumonia.