IC-101-01: Quantitative measures of brain tissue volumes in the elderly. The Rotterdam Scan Study

Abstract

Structural changes in the brain from adolescence into late adulthood have been quantified using magnetic resonance imaging. However, reliable population data for elderly people on volumetric measures of cerebrospinal fluid (CSF), grey matter and white matter are scarce. We quantified brain tissue volumes in a population–based study of the elderly and investigated how they were related to age, sex and the amount of white matter lesions (WML) and lacunar infarcts. This study was based on the Rotterdam Scan Study. In this population–based cohort study of non–demented elderly people, 490 participants (59–90 years) underwent T1–weighted, T2–weighted, Proton–Density and high–resolution Inversion–Recovery scans. We segmented images into grey matter, normal white matter, WML and CSF using multi–spectral k–nearest–neighbor classification and non–rigid atlas registration. Volumes were expressed as percentage of intra–cranial volume. Total white matter was defined as normal white matter and WML together. Brain infarcts were rated visually. Analyses were performed adjusting for sex and –if applicable– age. Average percentages of intra–cranial volume were 22.6% for CSF, 46.6% for grey matter, 29.5% for normal white matter and 1.35% for WML. With increasing age, we found larger volumes of CSF and WML and smaller volume of normal white matter. Despite increasing WML volume, total white matter volume decreased with increasing age (–0.35% per year; 95% confidence interval (CI): –0.41;–0.30). No significant association was found between age and grey matter volume. The effects of age were similar for men and women. Exclusion of persons with brain infarcts did not alter these results. Persons with more WML had more CSF (0.40% volume increase per standard deviation increase in WML; 95%CI: 0.14;0.66). The same was found for persons with lacunar brain infarcts as compared to persons without any infarct (1.2% larger CSF volume; 95%CI: 0.63–1.82). These relations with CSF were primarily due to smaller volume of total white matter, and not grey matter. In the elderly, volumes of CSF and WML increase with age, whereas white matter volume decreases. Grey matter volume does not change with age. The apparent loss of white matter is more pronounced in the presence of cerebral small vessel disease.