Lack of physical activity, neuropsychiatric symptoms and the risk of incident mild cognitive impairment in older community-dwelling individuals: A prospective cohort study

The present study examined the longitudinal association and interaction between lack of engaging in physical activity (PA) and presence of neuropsychiatric symptoms (NPS) with the risk of incident mild cognitive impairment (MCI). The authors conducted a prospective cohort study in the setting of the population-based Mayo Clinic Study of Aging in Minnesota, USA, involving 3083 cognitively unimpaired persons aged ≥ 50 years (1570 males; median age, 74 years). Predictors included: lack of engaging in light, moderate, and vigorous intensity PA within 1 year of baseline assessment as measured by a self-reported questionnaire; and presence of NPS (agitation, anxiety, apathy, appetite change, sleep/nighttime disturbance, depression, irritability, clinical depression, clinical anxiety) as measured by standardized tools. When the authors detected a statistically significant interaction, they compared the risk of incident MCI between four groups of participants (no NPS/engaging in PA = reference group; NPS/engaging in PA; no NPS/not engaging in PA; NPS/not engaging in PA) by calculating hazard ratios (HR) and 95% confidence intervals (CI) using Cox proportional hazard models adjusted for age (as time scale), sex, education, global cognition, medical comorbidities, and apolipoprotein E ɛ4 status. After a median follow-up of 6.3 years, 599 participants developed incident MCI. Not engaging in vigorous intensity PA and having sleep/nighttime disturbance (HR [95% CI], 1.61 [1.07, 2.43]; p = 0.021), clinical depression (1.98 [1.34, 2.92]; p < 0.001) or clinical anxiety (1.63 [1.11, 2.41]; p = 0.013) was associated with an increased risk of incident MCI as compared to the reference group. Thus, the combined presence of lack of vigorous intensity physical activity with sleep/nighttime disturbance behavior, clinical depression, or clinical anxiety was greater than the expected arithmetic sum of their independent effects. Neuropsychiatric symptoms appear to be a stronger driving force of incident MCI than lack of physical activity.