Science

Cristina Geroldi, MD, PhD; Giovanni B. Frisoni, MD; Giuseppe Paolisso, MD; Stefania Bandinelli, MD; Marco Lamponi, PT; Angela Marie Abbatecola, MD; Orazio Zanetti, MD; Jack M. Guralnik, MD, PhD; Luigi Ferrucci, MD, PhD

Objective: To test the association between cognitive impairment, with and without subcortical features, and insulin resistance in an elderly community-dwelling population.
Design: Cross-sectional wave of an epidemiologic longitudinal study (InCHIANTI).
Participants: A total of 523 people, aged 70 to 90 years without diabetes mellitus or hyperglycemia, from the InCHIANTI cohort were included in the study. A total of 119 individuals had cognitive impairment (Mini- Mental State Examination [MMSE] score or =25). Indicators of insulin resistance were the fasting plasma insulin level, insulin resistance index (Homeostasis Model Assessment of Insulin Resistance [HOMA-IR]), and insulin sensitivity index (Quantitative Insulin Sensitivity Check Index [QUICKI]).
Results: The insulin resistance profile of patients in the CI/SF+ group was similar to that of individuals who had experienced stroke, whereas the profile of individuals with cognitive impairment without subcortical features (CI/ SF− group) was similar to that of individuals in the no CI group. Patients in the CI/SF− group showed insulin resistance comparable to individuals in the no CI group (age-adjusted P=.27, .19, and .64, respectively, for difference in fasting blood insulin level, HOMA-IR, and QUICKI in linear regression models) and lower than patients with stroke (age-adjusted P = .01, .02, and .07, respectively). On the contrary, patients in the CI/SF+ group had insulin resistance and sensitivity values similar to those of the stroke group (age-adjusted P=.80, .84, and .75, respectively, for difference in fasting blood insulin level, HOMA-IR, and QUICKI) but significantly different from those in the no CI group (age-adjusted P = .01, .03, and .02, respectively).
Conclusions: Cognitive impairment with but not without subcortical features is associated with biochemical and clinical features of insulin resistance syndrome. In epidemiologic populations, insulin resistance might contribute to cognitive impairment through a vascular mechanism.