Public Health

Previous research suggests sex/gender differences in the association of body mass index (BMI; kg/m²) with cognition, but whether the association between BMI and cognitive decline varies by gender among racially-diverse older adults remains less understood.

Analyses used data from 1,711 participants in a harmonized cohort of racially/ethnically diverse older adults (LifeAfter90, KHANDLE, STAR) with BMI measured during mid- (ages 40-60) and late-life (≥65). Verbal episodic memory (VEM) and executive function (EF) were measured using z-standardized Spanish and English Neuropsychological Assessment Scales. Mid- and late-life BMI were obtained from the first available health records at each life stage and categorized into normal, overweight, and obese using race-specific cutoffs. Separate linear mixed models explored sex/gender differences in mid- and late-life BMI effects on cognitive decline using three-way interaction (sex/gender*BMI category*time) and sex/gender-stratified analyses. Models were adjusted for demographics, assessment-mode (in-person vs phone), and visit 1(Y/N) to account for practice-effects.

Participants were 62% women and had a mean age of 79±9.7 at first cognitive assessment (Table 1). At mid-life (mean BMI age=48±6.8), 22% of participants had obesity, 37% had overweight, and 41% had normal BMI. At late-life (mean BMI age=71±6.8), 36% of participants had obesity, 42% had overweight, and 21% had normal BMI. Neither mid- nor late-life BMI category were associated with EF decline, regardless of sex/gender (interaction p >0.10). Associations of mid-life obese BMI, mid-life overweight BMI, and late-life overweight BMI on VEM decline differed by gender (p <0.10). Stratified analyses found that among women, those with higher mid-life BMI had slower decline in VEM, though the difference was not significantly different than women with normal midlife BMI (overweight: (β(95%CI):0.03(-0.03,0.08); obese:0.01(-0.02,0.05)). Among men, those with obese BMI at mid-life had faster decline (-0.07(-0.14,-0.001)) than those with normal BMI. In late-life, women with higher BMI (obese: -0.03(-0.09,0.02), overweight:-0.05(-0.10,0.01)) trended towards a faster decline in VEM, whereas men with higher BMI at late-life (obese: 0.01(-0.05,0.08), overweight: (0.05(-0.01,0.11)) trended towards less decline (Figure 1).

These findings suggests that mid-life and late-life BMI may have differential associations with VEM in men and women. This may suggest differences in underlying mechanisms of cognitive decline between sex/gender.