Metabolic syndrome, inflammation, and nonamnestic mild cognitive impairment in older persons: a population-based study

Abstract

The metabolic syndrome (MetS) is more strongly associated with cognitive impairment in the presence of inflammation. This suggests that the association of MetS with mild cognitive impairment (MCI) may vary with the etiology and the subtype of MCI. This study investigated the association between MetS with or without inflammation and MCI [amnestic (a-MCI) and nonamnestic (na-MCI)]. We studied a randomly selected sample of 1969 participants (ages 70 to 89 y) from Olmsted County, MN, using the Clinical Dementia Rating Scale, a neurologic evaluation, and neuropsychologic testing. Data for participants were reviewed for a diagnosis of normal cognition, MCI, or dementia. Clinical components of MetS were ascertained by interview and confirmed from the medical records; biochemical measurements were assayed from a blood draw. We compared 88 na-MCI cases and 241 a-MCI cases with 1640 cognitively normal participants. MetS was not associated with either na-MCI or a-MCI. High C-reactive protein (CRP; highest tertile vs lowest tertile) was associated with na-MCI [odds ratio (OR)=1.85; 95% confidence interval (CI)=1.05, 3.24] but not with a-MCI, after adjusting for sex, age, and years of education. The combination of MetS and high CRP (compared to no MetS and lowest CRP tertile) was associated with na-MCI (OR=2.31; 95% CI=1.07, 5.00), but not with a-MCI (OR=0.96; 95% CI=0.59, 1.54). The combined presence of MetS and high levels of inflammation is associated with na-MCI in this elderly cohort, and suggests etiologic differences in MCI subtypes.

Figure

Distribution of C-reactive protein levels in subjects with and without the metabolic syndrome (MetS) in cognitively normal subjects, and in subjects with amnestic (a-MCI) and non-amnestic (na-MCI) MCI, with y-axis on a log scale. CRP levels were highest in subjects with na-MCI and metabolic syndrome (MetS). The lower and upper margins of the box represent the 25^th and 75^th percentiles; the line in the middle represents the median. The round circle in the middle of the box represents the mean, and circles outside of the box represent outliers that are greater than or less than 1.5 times the interquartile range. The short horizontal line connected to the box by a vertical line represents the largest and smallest values that are not considered outliers. The width of each box corresponds to the number of subjects in that group.