Association of Metabolic Syndrome and Inflammation with Cognitive Decline in Adults Aged 60 Years and Older: Findings from a National Health Survey in the United States
Objectives. We aimed to test the hypothesis that metabolic syndrome (MetS) is significantly associated with cognitive decline (CoD) in elderly adults and further assess whether MetS and inflammation have a significant joint effect on CoD. Methods. Data ( ) from the U.S. National Health and Nutrition Examination Survey (1999–2002) in participants aged ≥60 years who had Digit Symbol Substitution Tests (DSS: a standard measure of cognitive function) were studied. CoD was defined as those in the lowest quintile of DSS score. MetS was defined as having ≥3 of 5 MetS traits (large waist circumference (WC), high blood pressure (BP), elevated glucose, triglycerides, and decreased high density lipoprotein cholesterol). Results. Of 2975 participants, the prevalence of CoD (DSS score <25) was 12.1%. After adjusting covariates, individual large WC, high BP, elevated glucose level, and MetS were significantly associated with CoD in logistic regression models ( ). There was a significant dose-response relationship between an increased number of MetS traits and CoD ( ). A significant joint effect of MetS and CRP on the odds of CoD was observed. Conclusion. The study, using a nationally representative sample, extended previous studies by highlighting a significant MetS-CoD relationship and a joint effect of MetS and CRP on CoD. These novel findings add to our understanding of the association of neurometabolic disorders and cognition and have implications that may be relevant to primary care practice. 1. Introduction Impaired cognitive function is emerging as one of the greatest health threats of the twenty-first century. As the life expectancy of the population has increased so too has the prevalence of cognitive decline (CoD) and dementia, largely in the form of Alzheimer’s disease, which now affects almost 50% of adults over the age of 85 in the United States [1]. This startling figure will only grow as the average age of the population rises, so understanding the basis of CoD during ageing is critical [2]. Metabolic syndrome (MetS), a cluster of cofactors (large wait circumference, high blood pressure, elevated triglycerides, impaired glucose metabolism, and decreased high density lipoprotein cholesterol), and CoD are prevalent concomitants of aging. Cognitive function has been found to predict subsequent disability and mortality in elderly adults [3]. Although potential mechanisms remain obscure, they may include insulin resistance and inflammation leading to atherosclerosis, oxidative DNA damage, and CoD [2, 4]. For example, some studies have shown that
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