Contribution of Components of Metabolic Syndrome to Cognitive Performance in Middle-Aged Adults

Abstract

Introduction: Metabolic syndrome (MetS) has been associated with impaired cognition in different cognitive domains. This study investigated the association between MetS and cognitive functioning in middle-aged Bulgarians across different definitions of MetS severity.

Material and methods: Our cross-sectional sample included 112 participants (67 free of MetS and 45 with MetS) with a mean age of 50.04 ± 3.31 years. The following MetS variables were considered-presence of MetS, continuously measured MetS components, dichotomized MetS components, number of MetS components present, and Metabolic Syndrome Severity Score (MSSS). Participants' cognitive performance was assessed using the Consortium to Establish a Registry for Alzheimer's Disease Neuropsychological Battery (CERAD-NB). We employed multivariate regression models to investigate the associations between different measures of MetS severity and CERAD-NB total and subtest scores.

Results: Bivariate analyses showed that the CERAD-NB total score was significantly higher in women, participants with a university degree, those with normal blood pressure, normal waist circumference, and low triglyceride levels, compared with their counterparts. MetS participants had lower CERAD-NB total score (78.87 ± 6.89 vs. 84.97 ± 7.84) and specifically performed poorer on the subtest Word List Recall (7.16 ± 1.52 vs. 7.99 ± 1.52). These findings persisted after controlling for age, gender, and education. Next, generalized linear regression indicated that the CERAD-NB total score was lower in participants with MetS (β = -4.86; 95% confidence interval [CI]: -7.60, -2.11), those with more MetS components (β = -8.31; 95% CI: -14.13, -2.50 for fours vs. 0 components) and with an increase in MSSS (β = -3.19; 95% CI: -4.67, -1.71). Hypertension independently contributed to lower CERAD-NB total score (β = -4.00; 95% CI: -6.81, -1.19).

Conclusions: Across several definitions, MetS was associated with lower cognitive functioning, and MetS severity appeared to be a better predictor than most MetS components. Recognizing and reducing severity of MetS components might be helpful in supporting cognitive functioning. Further longitudinal research is needed to shed more light on the relationship between MetS and cognitive functioning across the life span.

Keywords: Alzheimer’s disease; Cardiovascular disease; Cerebrovascular disease/accident and stroke; Mild cognitive impairment.

Fig. 1

Restricted cubic spline model of the association between MSSS and cognitive functioning (CERAD-NB). Coefficients are unstandardized linear regression coefficients with their 95% CIs and represent the change in CERAD-NB per 1 unit increase in MSSS. Models are adjusted for age, gender, education, smoking status, and alcohol consumption. The effect of MSSS on CERAD-NB is statistically significant when the bounds of the 95% CI do not cross the reference line (zero) on the y-axis. MSSS value of “0” is the reference point. CERAD-NB = Consortium to Establish a Registry for Alzheimer’s Disease Neuropsychological Battery; CI = confidence interval; MSSS = Metabolic Syndrome Severity Score.