Association of Obesity With Cognitive Decline in Black and White Americans

Abstract

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 if the association between obesity and cognitive decline differs in Black and White adults. We hypothesized that obesity is associated with greater cognitive decline compared to normal weight, and that the impact of obesity on cognitive decline is more pronounced in Black adults compared to their White counterparts.Methods:We pooled data from 28,867 participants free of stroke and dementia (mean, standard deviation [SD]: age 61 [10.7] years at the first cognitive assessment, 55% female, 24% Black, and 29% obese) from six cohorts. The primary outcome was 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, standard deviation [SD] 10) at a participant's first cognitive assessment; a 1-point difference represents a 0.1 SD difference in global cognition across the six cohorts. The median follow-up was 6.5 years (25thpercentile, 75thpercentile: 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 BMI 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.

Towards a Deeper Understanding: Utilizing Machine Learning to Investigate the Association between Obesity and Cognitive Decline—A Systematic Review

“…Additionally, research has shown a connection between obesity in early old age and a decrease in cortical thickness [66]. These findings collectively suggest that obesity and its associated metabolic problems may contribute to increased microvascular brain damage and neuroinflammatory events, ultimately leading to cognitive decline [62].…”

“…Regrettably, the brain is not exempt from these inflammatory effects, which can ultimately accelerate the progression of cognitive decline and increase the risk of developing AD [60]. Obesity may be associated with higher levels of proinflammatory cytokines (like interleukin-1β) in the brain [61], which may explain why obesity remains linked to executive function even after accounting for blood pressure (BP) and fasting plasma glucose (FPG) [62]. Neuroinflammation related to obesity and activation of microglia induces synaptic remodeling and neuronal apoptosis and decreases neurogenesis, which has been associated with cognitive decline [63][64][65].…”

Weakness Thresholds Are Differentially Linked to Cognitive Function by Obesity Status in Older Americans

“…Indeed, physical activity participation is linked to lower AD/ADRD risk, but physical activity likewise helps in mitigating obesity and preserving muscle strength [ 29 ], and may have implications for cognitive function earlier in life [ 30 ]. Moreover, physical activity combats obesity [ 31 ], which in turn, is linked to executive function and dementia [ 32 ]. As such, physical activity could be particularly important for the triangulation between strength capacity, obesity status, and cognitive function.…”

Obesity-Induced Brain Neuroinflammatory and Mitochondrial Changes

“…Changes in cognitive function can be potentiated since middle-aged adults with obesity may experience differentially greater brain atrophy [ 37 ]. The relationship between a higher BMI and reduced cognitive performance does not change with age [ 45 ] or race [ 46 ]. A high intake of fat and sugar is associated with impairments in hippocampal-dependent learning and memory in children [ 47 ] and adults [ 48 , 49 ], suggesting a negative impact on hippocampal function across the lifespan.…”