Effect of age, period, and birth cohort on incapacity in community-dwelling elderly: the Bambuí Elderly Cohort (1997-2012)

Abstract:

Time trends in the prevalence rates of incapacity in the elderly can occur due to the effects of age, period, or cohort. Age is related to biological factors, the period to the subject’s environmental context, and the cohort to the subject’s exposures from birth to the present. The study aimed to verify which time dimensions most influence the evolution in the prevalence of incapacity in the elderly over the course of 15 years. Data were used from the Bambuí Elderly Cohort, and incapacity was assessed by report of “great difficulty” or “inability” to perform at least one of the activities related to mobility and basic and instrumental activities of daily living. The analysis was done with the age-period-cohort model for aggregate data, with calculation of the effects of time dimensions by analysis of deviance. A Poisson regression model determined the associations between age, period, and cohort and prevalence of incapacity, considering the total population and stratification by sex and schooling. Period effect was the most important for the three dimensions of incapacity, with an increase in prevalence at the start of the period, followed by a reduction over time, with minor differences in relation to sex and schooling. Cohort effect was significant, although less important than period effect. The results highlight the importance of analyzing the elder’s environment for reducing prevalence of incapacity, with an emphasis on policies and programs that can positively impact the time trend in this outcome, given the consistent effect of period observed in this study.

Keywords:
Aged; Disabled Persons; Age Effect; Period Effect; Cohort Effect