Cross-sectional association between physical activity level and subjective cognitive decline among US adults aged ≥45 years, 2015.

Subjective cognitive decline (SCD) is the self-reported experience of worsening or more frequent confusion or memory loss within the previous 12 months and can be one of the earliest symptoms of Alzheimer's disease. Regular physical activity can contribute to the primary, secondary, and tertiary prevention of cognitive decline. At the national level, prevalence estimates of SCD by physical activity level in the United States are currently unknown. The purpose of this study is to examine the prevalence of SCD and resulting functional limitations by physical activity level among US adults aged ≥45 years. Data from 33 states and the District of Columbia participating in the 2015 Behavioral Risk Factor Surveillance System (N = 128,925) were analyzed. We estimated the prevalence of SCD (a positive response to a question about worsening or more frequent confusion or memory loss within the previous 12 months) and resulting functional limitations overall and by self-reported physical activity level based on current guidelines (i.e., active, insufficiently active, and inactive). Odds ratios were estimated using logistic regression models adjusting for respondent characteristics. Overall, 11.3% of US adults aged ≥45 years reported SCD. Prevalence of SCD increased as physical activity level decreased (active: 8.8%; insufficiently active: 11.4%; inactive: 15.7%). Among those with SCD, the prevalence of functional limitations also increased as physical activity level decreased (active: 40.5%; insufficiently active: 50.0%; inactive: 57.4%). These differences largely remained after adjusting for respondent characteristics. Findings highlight the potential public health impact nationally of efforts to promote physical activity for cognitive health.