Heterogeneity in the dynamic change of cognitive function among older Chinese people: A growth mixture model

Our aim is to distinguish different trajectories of cognitive change in Chinese geriatric population and identify risk factors for cognitive decline in each subpopulation.

We obtained data from five waves (2002, 2005, 2008, 2011, 2014) of the Chinese Longitudinal Health Longevity Survey, using the Chinese Mini-Mental State Examination (C-MMSE) as a proxy for cognitive function. We applied growth mixture modeling (GMM) to identify heterogeneous subpopulations and potential risk factors.

Our sample included 3859 older adults, 1387 (48.7%) male and 1974 (51.2%) female with age range of 62 to 108 (average of 74.5) at initial survey. Using GMM and best fit statistics, we identified two distinct subgroups in respect to their longitudinal cognitive function: (a) cognitively stable (87.8%) group with 0.49 C-MMSE points decline per 3 years, and (b) cognitively declining (12.2%) group with 6.03 C-MMSE points decline per 3 years. Of note, cognitive activities were protective, and hearing and visual impairments were risk factors in both groups. Diabetes, hypertension, stroke and cardiovascular disease were associated with cognitive decline in the cognitively declining group. Physical activities, and intake of fresh vegetables, fruits, and fish products were protective in the cognitively stable group.

Using GMM, we identified heterogeneity in trajectories of cognitive change in older Chinese people. Moreover, we found risk factors specific to each subgroup, which should be considered in future studies.