High blood pressure and other vascular risk factors in mild cognitive impairment subtypes

Introduction. Mild cognitive impairment (MCI) is a syndrome featuring cognitive decline not interfering with activities of daily life. Different MCI subtypes have been described, including MCI with only memory impairment (A-MCI), MCI with involvement of a single non-memory domain (NA-MCI) and MCI with multiple-domain impairment (MD-MCI). From a prognostic point of view A-MCI is considered early Alzheimer’s Disease (AD), while NA-MCI and MD-MCI are thought to be heterogeneous conditions, underlying different pathological substrate including vascular pathology. Vascular risk factors (VRFs) have been identified as risk factors for MCI, but little is known about the role of VRFs in MCI subtypes. Aim. to investigate the association of different VRFs in MCI subtypes comparing the findings of subject with A-MCI with those of NA-MCI and MD-MCI. Methods. We performed a cross-sectional analysis of MCI population evaluated in a University-Hospital setting. Two hundred and fourteen subjects with MCI were included in the study: 39 with A-MCI, 28 with NA-MCI and 147 with MD-MCI. There were no significant differences among group in age (years: 74.3±8, 73.8±6 75.2±6.7, respectively), gender (female 51%, 64%, 54%) cognition (MMSE 25.7±2.5, 24.8±4.4, 24.8±2.9), mood (GDS 9.7±5.9, 10.5±6.3, 10.9±6.5), Hachinski ischemic score (2.2±0.9, 2.6±1.6, 2.6±1.1) and comorbilities as assessed with CIRS (0.43±0.22, 0.58±0.28, 0.51±0.27). Education was slightly lower in NA-MCI (5.7±2.7 years) with respect to A-MCI (8.9±4.2 years, p=0.007) Multinomial logistic regression analyses, adjusted for demographic variables when appropriate, were performed to evaluate the weight of VRFs in the development of the various MCI subtypes. Results. Hypertension revealed a stronger association with SD-MCI (OR 3.47; 95%CI 1.13 – 10.67) and MD-MCI (OR 7.81; 95%CI 3.48 – 17.50) respect to A-MCI .Hyperlipemia resulted the most frequent VRF in all MCI subgroups (81.8%, 76% and 70.8% in A-, NA- and MD-MCI respectively), without significant differences among groups. Discussion. Hypertension was associated with increased risk of all MCI subtypes, but the association was stronger with NA-MCI and MD-MCI. This association could reflect the role of high blood pressure in vascular cognitive impairment. The high frequency of hyperlipemia in all MCI subgroups, could reflect both the role of cholesterol metabolism in AD pathogenesis and the role of atherosclerosis in the development of vascular cognitive impairment. Due to the cross-sectional nature of this study, a relationship between VRFs and subsequent evolution in different subtypes of dementia could only be hypothesized.