Is midlife metabolic syndrome associated with cognitive function change? The Study of Women's Health Across the Nation.

CONTEXT: Metabolic syndrome (MetS) affects cognitive function in late life, particularly in women. But longitudinal research is scarce on associations of MetS with cognitive function during midlife. OBJECTIVE: To determine associations between MetS exposure and cognitive function trajectories in midlife women. DESIGN AND SETTING: This is a 17-year prospective, longitudinal study of multiracial/ethnic women in 7 US communities, with annual/biennial assessments. PARTICIPANTS: Participants were 2149 US women traversing menopause. EXPOSURE: Exposure consisted of MetS assessments (median 4 assessments over 4 years). MAIN OUTCOME MEASURES: Main outcome measures were assessments of cognitive function in 3 domains: perceptual speed (symbol digit modalities test, SDMT), episodic memory (East Boston Memory Test, EBMT), and working memory (Digit Span Backward Test, DSB). RESULTS: By their first cognitive assessment (age 50.7 +/- 2.9 years), 29.5% met the criteria for MetS. Women completed a median (interquartile range [IQR]) of 6 (IQR 4-7) follow-up cognitive assessments over 11.2 (IQR 9.2-11.5) years. Women with MetS, compared with those without, had a larger 10-year decline in SDMT z-score (estimate -0.087, 95% confidence interval, -0.150 to -0.024; P = 0.007), after adjustment for cognitive testing practice effects, sociodemographics, lifestyle, mood, and menopause factors. As such, MetS accelerated the 10-year loss of perceptual speed by 24%. MetS did not differentially affect the rate of decline in either immediate (P = 0.534) or delayed (P = 0.740) episodic memory or in working memory (P = 0.584). CONCLUSIONS: In midlife women MetS exposure was associated with accelerated decline in perceptual speed, but not episodic or working memory.