Evolution of self-rated health status in the elderly: cross-sectional vs. longitudinal estimates.

We assessed the perceived health status evolution among elderly subjects and examined the age-related differences in perceived health when comparing estimates obtained from cross-sectional and longitudinal approaches. Data come from a cohort of non-institutionalized individuals aged 65 years or older, living in Barcelona, Spain. One thousand three hundred fifteen (1315) elderly were successfully interviewed at baseline in 1986 and 754 (84.6% of the eligible) at the re-assessment (1993-1994). Estimates of change in perceived health status were calculated based on cross-sectional and longitudinal approaches. Cross-sectionally, no significant differences in the proportion of individuals with poor self-rated health were found (40.5 vs. 42.5%, P = 0.90). Among survivors, the proportion of individuals with poor health increased from 37.8% to 55.1% (P < 0.01), an 8.7-fold decline of perceived health when compared with the cross-sectional estimates. Comorbidity (aOR 2.1; 95%CI: 1.4-3.3) and no education (aOR 1.9; 95%CI: 1.1-3.2) were associated with a decline in health status after adjusting by baseline health status. We recommend the use of longitudinal studies to understand the evolution of perceived health in the elderly.