Insulin resistance and cognitive test performance in elderly adults: National health and nutrition examination survey (NHANES)

Abstract

ObjectivesTo examine the relationship between homeostatic model of insulin resistance (HOMA-IR) and cognitive test performance among population≥60years in a national database. HypothesisHigher insulin resistance is associated with lower cognitive test performance score in the population≥60years. ParticipantsWe analyzed data from the National Health and Nutrition Examination Survey (NHANES) 1999–2000 and 2001–2002. MeasurementsCognitive test performance was measured by the Digit Symbol Substitution (DSS) exercise score. The main independent variable was the homeostasis model assessment of insulin resistance (HOMA-IR). We used bivariate analysis and generalized linear model adjusting for age, gender, race, education, body mass index, and systolic and diastolic blood pressures; total cholesterol, low density lipoprotein (LDL), high density lipoprotein (HDL) and triglyceride levels; and physical activity, diabetes mellitus, stroke, and congestive heart failure. STATA 14 was used to analyze the data taking into consideration the design, strata and weight. ResultsOf the 1028 participants, 44% were male and 85% were white. The mean age was 70.0±0.28 (SE) years. Their average HOMA-IR was 3.6±0.14 and they had a mean of 49.2±0.8 correct DSS score in the cognitive test. Adjusting for the confounding variables, HOMA-IR was associated with decline in DSS score (B=−0.30, 95% confidence interval=−0.54 and −0.05, p=0.01). The model explained 44% of the variability of the DSS score (R2=0.44). Significant predictors of decline in DSS score were age, gender, race, and education (p=0.01). ConclusionInsulin resistance as measured by HOMA-IR was independently associated with lower cognitive test performance score among elderly participants aged ≥60years. Longitudinal studies are needed to test the mechanism and the causal relationship.