The combined associations of physical activity and body mass index on the prevalence of functional difficulties among 29,343 individuals living with subjective cognitive decline: a cross-sectional study

Background Functional difficulties associated with subjective cognitive decline (SCD) represent a public health concern. While physical activity (PA) and body mass index (BMI) are associated with cognitive health, their combined association with functional difficulties is unclear. This study examined the combined associations of PA and BMI on the prevalence of functional difficulties in a nationally representative sample of U.S. adults living with SCD.Methods BRFSS data from 2011, 2015, 2017, and 2019 were pooled. Cross-sectional associations between independent and combined PA and BMI levels were estimated using Poisson log-linear regression and reported by Adjusted Prevalence Ratios (APRs).Results Data from 29,343 adults (≥18 years) were included. Compared to the reference group (Highly Active, Normal Weight), individuals with lower PA and increased BMI were more likely to report functional difficulties; APRs ranged from 1.10, 95% CI: 1.10–1.11 (Nonactive, Normal Weight) to 1.19, 95% CI: 1.18–1.19 (Nonactive, Obesity). Meeting PA guidelines reduced the prevalence of functional difficulties across all BMI categories, though benefits were smaller among individuals with obesity.Conclusion Low PA and higher BMI were associated with greater prevalence of SCD functional difficulties. Guideline-level PA may reduce difficulties among BMI groups, but to a lesser extent among individuals living with obesity, supporting tailored PA strategies.