1445-P: Physical Activity and Insulin Resistance in Midlife Women: 17-Year Longitudinal Associations in SWAN

Insulin resistance increases starting in midlife due to decreasing estrogen production and other aging-related factors. Higher intensity physical activity (PA) has the potential to attenuate rising insulin resistance; however, longitudinal associations of PA and insulin resistance have not been studied in midlife women. We used data from the Study of Women’s Health Across the Nation (SWAN, N=3,230), a cohort study with up to 17 years of follow-up, to estimate longitudinal associations of higher intensity PA with insulin resistance. Women reported PA using the Kaiser Physical Activity Survey at 7 study visits (V0, V3, V5, V6, V9, V12, V13). We used the sports and exercise physical activity index score (range: 1-5) to assess leisure-time moderate to vigorous intensity PA (MVPA). SWAN measured glucose and insulin in blood collected at 8 study visits (V0, V1, V3-V7, V12, V13). We used generalized estimating equations to estimate the adjusted longitudinal associations of MVPA with homeostatic model assessment of insulin resistance (HOMA-IR) overall, by baseline body mass index (BMI) category, and by race/ethnicity. Women were 46 (SD=3) years old at baseline. Forty-seven percent were non-Hispanic white; 28% black; 9% Japanese; 8% Chinese, and 8% Hispanic. Each additional one-unit increase in reported MVPA was associated with an average 0.2 unit lower HOMA-IR (95% CI: -0.3, -0.1) over time. Associations differed by baseline BMI (interaction P<0.001). Reported MVPA was associated with a 0.1 lower HOMA-IR (95% CI: -0.1, -0.02) in normal weight women, a 0.2 lower HOMA-IR (95% CI: -0.3, -0.1) in overweight women, and a 0.4 lower HOMA-IR (95% CI: -0.6, -0.1) in obese women. MVPA was not associated with HOMA-IR in underweight women (mean difference=0.0; 95% CI: -0.1, 0.1). Associations did not differ by race/ethnicity (interaction P=0.39). Our findings support longitudinal associations of MVPA with lower insulin resistance in midlife women, with the strongest associations in obese women.