Executive dysfunction assessed by Clock-Drawing Test in older non-demented subjects with metabolic syndrome is not mediated by white matter lesions.

Abstract

Metabolic syndrome (MetS) has been associated with greater occurrence of white matter hyperintensities (WMH). It remains uncertain whether MetS as a construct is associated with poorer cognitive performances. This study explores whether MetS is associated with poorer performances in global and domain-specific cognitive tests in older non-demented subjects independently of its individual components, WMH severity and other variables. MetS was diagnosed according to the National Cholesterol Education Program Adult Treatment Panel III definition. Brain magnetic resonance studies (1.5T) were performed. Deep and periventricular WMH were graded using the Fazekas scale. Subjects underwent the Mini-Mental State Examination, the Babcock Short Story Recall test and the Clock-Drawing Test (CDT). Eighty community-dwellers aged 67-91 years were studied. Subjects with MetS (n = 35) had more severe WMH, and poorer performances on the CDT (P = 0.003) and the Babcock Short Story Recall test (P = 0.027). After multiple adjustment, MetS was inversely associated with CDT scores (B = -1.285; 95% confidence interval = -1.996--0.575; P = 0.001) but not with episodic memory. Results were not affected by WMH severity. Interestingly, none of the individual components of MetS predicted poorer cognitive performances. Impairment in executive functions assessed by CDT may represent an early and specific sign of cognitive decline in older individuals with MetS. Future longitudinal studies are needed to better establish the predictive role of MetS on dementia and to demonstrate the possibility of dementia prevention by targeting MetS.