Physical Frailty, Cognitive Impairment, and the Risk of Neurocognitive Disorder in the Singapore Longitudinal Ageing Studies

The independent and combined effects of physical and cognitive domains of frailty in predicting the development of mild cognitive impairment (MCI) or dementia are not firmly established. This study included cross-sectional and longitudinal analyses of physical frailty (Cardiovascular Health Study criteria), cognitive impairment (Mini-Mental State Examination [MMSE]), and neurocognitive disorder (DSM-5 criteria) among 1,575 community-living Chinese older adults from the Singapore Longitudinal Ageing Studies. At baseline, 2% were frail, 32% were prefrail, and 9% had cognitive impairment (MMSE score < 23). Frailty at baseline was significantly associated with prevalent cognitive impairment. Physical frailty categories were not significantly associated with incident NCD, but continuous physical frailty score and MMSE score showed significant individual and joint associations with incident mild NCD and dementia. Compared with those who were robust and cognitively normal, prefrail or frail old adults without cognitive impairment had no increased risk of incident NCD, but elevated odds of association with incident NCD were observed for robust with cognitive impairment (odds ratio [OR] = 4.04, p < .001), prefrail with cognitive impairment (OR = 2.22, p = .044), and especially for frail with cognitive impairment (OR = 6.37, p = .005). The prevalence of co-existing frailty and cognitive impairment (cognitive frailty) was 1% (95% confidence interval [CI]: 0.5-1.4), but was higher among participants aged 75 and older at 5.0% (95% CI: 1.8-8.1). Physical frailty is associated with increased prevalence and incidence of cognitive impairment, and co-existing physical frailty and cognitive impairment confers additionally greater risk of incident NCD.