Objectives: It remains uncertain whether the favorable trend of reduction in physical disabilities has become reversed in the recent-born cohorts of older adults. This study aimed to compare the rate of decline with time in self-reported Instrumental Activity of Daily Living (IADL) difficulties, objective measurement of gait speed and grip strength, in three birth cohorts of Chinese older adults.
Design: A prospective cohort study.
Setting and participants: Four thousand Chinese older adults aged 65 years or above in three birth cohorts (1934-1938, 1929-1933, 1905-1928) were recruited from the community in Hong Kong.
Measurements: Grip strength, gait speed and IADL difficulties were measured between 2001 to 2017. Joint models were used to examine the trajectories of grip strength, gait speed and IADL difficulties over time, and the interaction effect of age-by-cohort (or also age2-by-cohort) was also examined.
Results: The recently born cohort (1934 - 1938) had worse grip strength and more IADL difficulties at the same age than the earlier two cohorts (1929 - 1933; 1905 - 1928). Furthermore, the most recently born cohort also followed a more rapid decline longitudinally with a greater decline observed in gait speed, grip strength and IADL difficulties for women whereas a greater decline in grip strength and IADL difficulties for men.
Conclusions: The continuous improvement of physical limitations in old age may have halted and there appears to be a reversal of this favourable trend in the recent born cohort of older adults living in Hong Kong.
Keywords: Chinese older people; Physical function; age-by-cohort; cohort; trajectories.