Which reduces the risk of cognitive impairment: physical activity or daytime nap?

Abstract

Dear Editor, Qian et al. conducted a cross-sectional study to investigate the association between three lifestyles and cognitive impairment (COI) in adults aged 60 years or older. The adjusted odds ratios (ORs) (95% confidence intervals (CIs)) of tea consumption, physical activity for COI were 0.66 (0.48–0.90) and 0.79 (0.65–0.96), respectively. In addition, the adjusted OR (95% CI) of physical activity plus siesta for COI was 0.44 (0.31–0.64). Although almost all combinations of lifestyle factors had a significant negative association with COI, the adjusted OR of tea consumption plus siesta for COI did not reach the level of significance. Tea consumption and siesta are lifestyles without body movement, and physical activity may be indispensable to avoid COI. I present some information regarding siesta and cognition. Duan et al. conducted a prospective study to examine the association between sleep characteristics and mild cognitive impairment (MCI) incidence with special reference to apolipoprotein E polymorphism ε4 (APOEε4). The adjusted hazard ratios (HRs) (95% CIs) of taking a nap at noon for MCI were 0.723 (0.592– 0.883) and 0.719 (0.576–0.897) in all participants and in APOEε4 non-carriers, respectively. They concluded that MCI was protected by nap regardless of APOEε4. Palpatzis et al. reported that the adjusted HR (95% CI) of daytime napping in middle-aged adults for dementia incidence was 1.67 (1.37–2.03). They also observed that the elevated dementia risk was observed regardless of genetic risk by APOE genotype. On this point, the effect of APOE on the association between sleep and incident dementia may differ in middle-aged people and older adults, because the effects of APOEε4 can vary with age and other factors. Furthermore, Riaz et al. reported that APOEε4 presented different risks of cognitive decline and dementia. Anyway, clinical outcome and age should be treated with caution, when APOEε4 is included for the analysis. Finally, Li et al. reported the association between daytime napping and subsequent risk of Alzheimer’s dementia. Longer and more frequent daytime naps were significantly associated with higher risk of Alzheimer’s dementia. In addition, there were bidirectional dose–response relationships between longer and/or more frequent daytime napping and worse levels of cognition. Causal association should be specified by further studies.