Factors affecting attrition in the Baltimore Longitudinal Study of Aging

In a longitudinal study of aging, the influence on attrition of age, marital status, education, occupation, distance between a subject's residence and study center, self-health and financial assessment, and method of recruitment was examined. Prospective, follow-up information on the subsequent active/dropout and alive/dead status on the 1088 subjects, who joined the Baltimore Longitudinal Study of Aging during the first twenty years (1958-1977), were studied using a proportional hazards model. Three analyses, each controlling for death in a different manner, produced similar results. The analysis indicates that age, education and distance have the strongest association with attrition (p less than 0.001), while self-health assessment has a lesser association (p less than 0.05). The lowest risk in age, for example, occurs in 40-49.9 year olds with subjects less than 30 having an increased risk of 91% and subjects 70 or older having an increased risk of 189%. Examination of attrition probabilities show that subjects living 500 or more miles from study center, ages 70 and older, with less than bachelors degree, and perceiving their health as average or below have the greatest probability of dropping out-approximately 3-fold greater than the average subject's probability.