Cigarette Smoking, Alcohol Consumption, and Risk of ARDS* A 15-Year Cohort Study in a Managed Care Setting Carlos Iribarren, MD, MPH, PhD; David R. Jacobs, Jr., PhD; Stephen Sidney, MD; Myron D. Gross, PhD; and Mark D. Eisner, MD Study objective: To examine the association of cigarette smoking and alcohol consumption with hospital presentation of ARDS in a well-defined, multiethnic population. Design: Retrospective cohort study. Setting: Health maintenance organization in Northern California. Participants: A total of 121,012 health plan subscribers (54.2% women), aged 25 to 89 years. Outcome measure: Hospital presentation of ARDS (validated by medical chart review) from baseline in 1979 to 1985 through the end of 1993 (median, 9.9 years). Results: There were 56 cases of ARDS (33 in men, 23 in women). The case fatality rate was 39% in both genders. ARDS was independently related to increasing age (rate ratio of 10 years, 1.38; 95% confidence interval [CI], 1.12 to 1.71), to current smoking of < 20 cigarettes/d (rate ratio vs never cigarette smokers, 2.85; 95% CI, 1.23 to 6.60), and to current cigarette smoking of > 20 cigarettes/d (rate ratio vs never smokers, 4.59; 95% CI, 2.13 to 9.88). No association was observed between alcohol consumption and ARDS. Conclusions: The results of this study suggest a relationship (with evidence of dose-response effect) between cigarette smoking and ARDS. Assuming a causal relationship, approximately 50% of ARDS cases were attributable to cigarette smoking. (CHEST 2000; 117:163–168) Key words: alcohol; ARDS; epidemiology; risk factors; smoking Abbreviations: BMI = body mass index; ICD-9 = Ninth Revision of the International Classification of Diseases T he ARDS is a severe clinical picture defined by the presence of dyspnea, tachypnea, hypox- emia, radiographic evidence of bilateral chest infiltrates, and decreased respiratory compliance, and is caused by inflammatory-cell-mediated en- dothelial lung injury. 1–3 It is a rapidly progressive syndrome, with an overall fatality rate of 40 to 60%. 1,4,5 Since there is no specific treatment modality, the identification of patients at higher risk for the devel- opment of ARDS is paramount. Well-established clinical (or proximal) predictors of ARDS include sepsis, aspiration of gastric contents, and major trauma. 5–11 However, less is known about nonproxi- mal factors that may increase the likelihood of eventually developing ARDS. Cigarette smoking and alcohol consumption are potential nonproximal risk factors for ARDS. First, smoking increases the risk of many lung and systemic disorders predating ARDS, 12–16 and secondly, ciga- rette smoke contains highly reactive hydroxyl radicals capable of causing membrane peroxidation, 17 dam- age to DNA, 18 and inflammatory reactions. 12–16 In turn, chronic heavy alcohol consumption has been linked to trauma outcomes, 19,20 and to increased risk of complication during the course of hospitaliza- tion. 21 The aim of this study was to test the hypothesis of whether cigarette smoking and alcohol consumption are independent risk factors for subsequent presen- tation of ARDS in a well-defined, multiethnic pop- ulation. *From the Kaiser Permanente Division of Research (Drs. Irib- arren and Sidney), Oakland, CA; the Division of Epidemiology, School of Public Health (Drs. Jacobs and Gross), University of Minnesota, Minneapolis, MN; and the Department of Medicine, Division of Pulmonary and Critical Care Medicine and Cardio- vascular Research Institute (Dr. Eisner), University of California, San Francisco, CA. This study was supported by contract RO1-AG-12264 – 01A1 from the National Institute on Aging, National Institutes of Health, Bethesda, MD. Manuscript received February 23, 1999; revision accepted June 16, 1999. Correspondence to: Carlos Iribarren, MD, MPH, PhD, Kaiser Permanente Division of Research, 3505 Broadway, Oakland, CA 94611; e-mail: cgi@dor.kaiser.org CHEST / 117 / 1 / JANUARY, 2000 163