The authors examined the effects of cognitive function, as assessed by the Mini-Mental State Examination, and drug use on the incidence of hip fracture in a community-based Swedish population of 1,608 subjects who were aged ≥75 years on October 1,1987, and who had not had a hip fracture. During the 7,123.8 person-year follow-up, 134 first hip fractures were identified. The Cox proportional hazards model was used to estimate the relative risk of developing hip fracture, taking into account several potential confounders. Compared with those without cognitive impairment, subjects with mild impairment (Mini-Mental State Examination scores 18–23) had a relative risk of 2.04 (95% confidence interval (Cl) 1.29–3.24), and subjects with moderate-severe impairment (Mini-Mental State Examination score <18) had a relative risk of 2.09 (95% Cl 1.17–3.72). Subjects using opioid analgesics (97% took propoxyphene) had a relative risk of 2.01 (95% Cl 1.19–3.40). Taking potassium supplements (99% took potassium chloride) was related to a reduced risk of hip fracture (relative risk = 0.55, 95% Cl 0.31–0.98), while diuretics did not have an independent impact. In summary, the results show that cognitive impairment and use of propoxyphene are associated with increased risk of hip fracture. The observed protection of potassium chloride merits further attention. The limitation of the study was that the assessment of drug use was made only at baseline. Am J Epidemiol 1998; 148:887–92. [ABSTRACT FROM AUTHOR]