Cigarette smoking and invasive pneumococcal disease.

Background: Approximately half of otherwise healthy adults with invasive pn eumococcal disease are cigarette smokers. We conducted a population-based c ase-control study to assess the importance of cigarette smoking and other f actors as risk factors for pneumococcal infections. Methods: We identified immunocompetent patients who were 18 to 64 years old and who had invasive pneumococcal disease (as defined by the isolation of Streptococcus pneumoniae from a normally sterile site) by active surveillan ce of laboratories in metropolitan Atlanta, Baltimore, and Toronto. Telepho ne interviews were conducted with 228 patients and 301 control subjects who were reached by random-digit dialing. Results: Fifty-eight percent of the patients and 24 percent of the control subjects were current smokers. Invasive pneumococcal disease was associated with cigarette smoking (odds ratio, 4.1; 95 percent confidence interval, 2 .4 to 7.3) and with passive smoking among nonsmokers (odds ratio, 2.5; 95 p ercent confidence interval, 1.2 to 5.1) after adjustment by logistic-regres sion analysis for age, study site, and independent risk factors such as mal e sex, black race, chronic illness, low level of education, and living with young children who were in day care. There were dose-response relations fo r the current number of cigarettes smoked per day, pack-years of smoking, a nd time since quitting. The adjusted population attributable risk was 51 pe rcent for cigarette smoking, 17 percent for passive smoking, and 14 percent for chronic illness. Conclusions: Cigarette smoking is the strongest independent risk factor for invasive pneumococcal disease among immunocompetent, nonelderly adults. Be cause of the high prevalence of smoking and the large population attributab le risk, programs to reduce both smoking and exposure to environmental toba cco smoke have the potential to reduce the incidence of pneumococcal diseas e. (N Engl J Med 2000;342:681-9.) (C)2000, Massachusetts Medical Society.