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Association of Obesity With Cognitive Decline in Black and White Americans
Emmanuel Quaye1, Andrzej T Galecki1, Nicholas Tilton1
1From the University of Michigan Medical School (E.Q.), Ann Arbor; Departments of Internal Medicine and Cognitive Health Services Research Program (A.T.G., N.T., R.W., D.A.L.), Biostatistics (A.T.G.), Psychiatry and Michigan Alzheimer's Disease Center (E.M.B.), and Neurology and Stroke Program (D.A.L.), University of Michigan, Ann Arbor; Department of Neurology (M.S.V.E.), Vagelos College of Physicians and Surgeons, and Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY; Department of Epidemiology (A.L.F., S.R.H., M.D.J.), School of Public Health, University of Washington, Seattle; Department of Neurology (R.F.G.), and Department of Epidemiology (A.L.G.), Bloomberg School of PublicHealth, Johns Hopkins University, Baltimore, MD; Department of Biostatistics (M.G.), University of Mississippi School of Medicine, Jackson, MS; Departments of Internal Medicine and Epidemiology and Prevention (T.M.H.), Wake Forest School of Medicine, Winston-Salem, NC; Department of Neurology (M.D.J.), School of Medicine, University of Washington, Seattle; Department of Neurology (R.L.S./M.S.), University of Miami Leonard School of Medicine, FL; Kaiser Permanente Northern California Division of Research (S.S.), Oakland; Department of Internal Medicine (B.G.W.), University of Mississippi School of Medicine, Jackson; and Departments of Psychiatry (K.Y.), Neurology and Epidemiology, University of California, San Francisco.
Background And Objectives:
There are disparities in the prevalence of obesity by race, and the relationship between obesity and cognitive decline is unclear. The objective of this study was to determine whether obesity is independently associated with cognitive decline and whether the association between obesity and cognitive decline differs in Black and White adults. We hypothesized that obesity is associated with greater cognitive decline compared with normal weight and that the effect of obesity on cognitive decline is more pronounced in Black adults compared with their White counterparts.
Methods:
We pooled data from 28,867 participants free of stroke and dementia (mean, SD: age 61 [10.7] years at the first cognitive assessment, 55% female, 24% Black, and 29% obese) from 6 cohorts. The primary outcome was the annual change in global cognition. We performed linear mixed-effects models with and without time-varying cumulative mean systolic blood pressure (SBP) and fasting plasma glucose (FPG). Global cognition was set to a t-score metric (mean 50, SD 10) at a participant's first cognitive assessment; a 1-point difference represents a 0.1 SD difference in global cognition across the 6 cohorts. The median follow-up was 6.5 years (25th percentile, 75th percentile: 5.03, 20.15).
Results:
Obese participants had lower baseline global cognition than normal-weight participants (difference in intercepts, -0.36 [95% CI, -0.46 to -0.17]; p < 0.001). This difference in baseline global cognition was attenuated but was borderline significant after accounting for SBP and FPG (adjusted differences in intercepts, -0.19 [95% CI, -0.39 to 0.002]; p = 0.05). There was no difference in the rate of decline in global cognition between obese and normal-weight participants (difference in slope, 0.009 points/year [95% CI, -0.009 to 0.03]; p = 0.32). After accounting for SBP and FPG, obese participants had a slower decline in global cognition (adjusted difference in slope, 0.03 points/year slower [95% CI, 0.01 to 0.05]; p < 0.001). There was no evidence that race modified the association between body mass index and global cognitive decline (p = 0.34).
Discussion:
These results suggest that obesity is associated with lower initial cognitive scores and may potentially attenuate declines in cognition after accounting for BP and FPG.
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