Apathy is associated with greater decline in subjective, but not in objective measures of physical functioning in older people without dementia

Background: In older people, both apathy and depression (which frequently co-occurs with apathy) have been associated with poor physical functioning, a major health concern. We investigated the association between apathy and physical functioning in older people without dementia and whether this association is modified by depression. Methods: We used the data from 380 older participants (with and without depression) taking part in the Netherlands Study of Depression in Older Persons, with baseline scores on the Apathy Scale and baseline and 2-year follow-up scores on at least one measure of physical functioning. These included the International Physical Activities Questionnaire (IPAQ, self-reported), WHO Disability Assessment Schedule (WHO-DASII mobility subset, self-reported), walking speed, or handgrip strength. Multivariable linear regression analyses were performed to examine the association between apathy at baseline and physical functioning at 2-year follow-up. We also investigated effect modification by sex, age, and depression. Results: Cross-sectionally, participants with higher baseline Apathy Scale scores performed significantly worse on all measures of physical functioning. Longitudinally, higher baseline Apathy Scale scores were associated with higher delta scores on the IPAQ (B = -59.81) in the basic model, and higher delta scores on the WHO-DASII (B = .09) in all models. Apathy was not associated with higher delta scores for walking speed or handgrip strength. Furthermore, sex, age, and depression did not modify any association. Conclusion: In a Dutch cohort of older people without dementia, apathy was associated with more decline in self-reported, but not in objective physical functioning. Sex, age, and depression did not modify these associations. In older people with apathy, subjective decline may precede decline in physical performance tests.