Risk Factors for the Development of Community-Acquired Pneumonia in Young Adults

Background: Community-acquired pneumonia (CAP) is a common and severe illness. The factors thought to predispose to development of CAP in young patients have not previously been reported. We, therefore, conducted a retrospective case­control study to assess the risk factors and the clinical aspects of CAP in young adult patients.

Methods: We studied fifty-six patients (age <40 years) who were seen in both a university hospital and a community hos­pital from January 1995 to November 1998. They were matched by sex and age with fifty-six control subjects. The diagnostic criteria for CAP were based on clinical and radiological find­ings. Patients with human immunodeficiency virus infection, transplant recipients, those with neoplasia or autoimmune dis­orders, and those treated with high doses corticosteroids were excluded. Risk factors including habits, medical history, physi­cal examination and radiographical findings, laboratory data and treatments were recorded.

Results: The mean age was 29 years (range, 16 to 40 years). Etiological diagnosis was achieved in 12 patients (21.4%): 8 S. pneumoniae (7 in sputum and 1 in pleural fluid), 3 L. pneu­mophila and 1 M. pneumoniae. Lobar consolidation was the most prevalent radiographical presentation and extrapul- monary symptoms were seen in 36% of the patients. In the uni­variate analysis, an increased risk of CAP was associated with ex and current smoking, hypoalbuminemia, previous pneumo­nia or recent respiratory infection. In the multivariate analysis, the only statistically significant risk factor for CAP was ex and current smoking (Odds ratio=2.5; 95% confidence interval 1.02- 6.43, p=0.046).

Conlusions: This study revealed that smoking is the most important risk factor for CAP in young adults. Preventive mea­sures will reduce the risk of pneumonia in this age group.