Study Design

The study population is composed of community dwelling elderly people between 65 and 74 years of age. The sample was stratified by sex with an aim to recruit 200 men and 200 women at each site. The total attained sample size of the study at the five research sites was 1995. The sample size at each site was calculated to allow for comparison of baseline mobility disability prevalence of men and women assuming a prevalence ratio of 1.8, error type I of 0.05 and power of 0.80.