Late-life Physical Exercise, Neuropsychiatric Symptoms And The Risk Of Incident Mild Cognitive Impairment

Abstract

PURPOSE: Mild cognitive impairment (MCI) is the intermediate stage between normal cognitive aging and dementia. We examined the association between lack of engaging in physical exercise (PE) and presence of neuropsychiatric symptoms (NPS), both separately and combined, with the outcome of incident MCI. METHODS: This prospective cohort study in the setting of the population-based Mayo Clinic Study of Aging in Olmsted County, MN, included 3206 cognitively unimpaired persons aged ≥ 50 years (1629 males; 853 APOE ɛ4 carriers; 74 years median age). The outcome of interest in the Cox proportional hazard models was incident MCI, with age as the time scale. Predictors were lack of engaging in light, moderate and vigorous intensity PE within one year of baseline assessment; and presence of NPS (agitation, anxiety, apathy, appetite change, nighttime behavior, depression, and irritability) as measured by the Neuropsychiatric Inventory Questionnaire. We also compared the risk of incident MCI between four groups of participants: no NPS/ engaging in PE (reference group); NPS/ engaging in PE; no NPS/ not engaging in PE; and NPS/ not engaging in PE. Analyses were adjusted for sex, education, global cognition, medical comorbidities, and Apolipoprotein E (APOE) ɛ4 status. RESULTS: After a median follow-up of 5.3 years, 599 participants developed incident MCI. Individuals who did not engage in light (HR [95% CI]; 1.25 [1.00, 1.55]), moderate (1.19 [1.00, 1.41]) or vigorous intensity PE (1.36 [1.01, 1.83]) had an increased risk of incident MCI. Having anxiety (1.60 [1.09, 2.33]), apathy (1.91 [1.39, 2.62]) or depression (1.66 [1.30, 2.12]) was also associated with an increased risk of incident MCI. Participants who did not engage in PE (be it of light, moderate or vigorous intensity) in the presence of NPS had the highest risk of incident MCI. For example, not engaging in moderate intensity PE and having anxiety (1.94 [1.20, 3.15]), apathy (2.04 [1.34, 3.13]) or depression (1.93 [1.41, 2.66]) was associated with an increased risk of incident MCI as compared to the reference group. CONCLUSIONS: Lack of engaging in late-life PE and NPS are independent risk factors of incident MCI. A combination of both factors is associated with an even more elevated risk of developing MCI, with NPS appearing to be a stronger driving force than lack of PE.