HOSPITAL CONTROLS VERSUS COMMUNITY CONTROLS - DIFFERENCES IN INFERENCES REGARDING RISK-FACTORS FOR HIP FRACTURE

In case-control studies using cases identified from persons admitted t o hospitals, two types of controls are most often used: persons from t he communities served by the hospitals and persons admitted to the sam e hospitals as those to which the cases were admitted, It is often unc lear which is the more appropriate choice, and whether the use of one or the other type of control group will lead to biased conclusions, Th e purpose of the present analysis was to determine whether the choice of hospital controls versus community controls would influence conclus ions regarding risk factors for hip fracture, Cases (n = 425), hospita l controls (n = 312), and community controls (n = 454) were drawn from a case-control study of risk factors for hip fracture in women, Study participants were white and black women aged 45 years or older and li ving in New York City or Philadelphia, Pennsylvania, who were selected between September 1987 and July 1989, Using community controls but no t hospital controls, investigators would have concluded that having a fall during the previous 6 months, current smoking, and moving during the previous year were associated with an increased risk of hip fractu re, Associations of hip fracture risk with stroke and prior use of amb ulatory aids were stronger using community controls, but associations with estrogen use and body mass index were not influenced by choice of control group, Community controls were quite similar to representativ e samples of community-dwelling elderly women, whereas hospital contro ls were somewhat sicker and more likely to be current smokers. The aut hors conclude that community controls comprise the more appropriate co ntrol group in case-control studies of hip fracture in the elderly.