Factors associated with morphometric brain changes in cognitively normal aging

OBJECTIVE: Cognitive impairment is associated with reductions in brain weight and volume. The factors related to morphometric brain changes in cognitively normal aging remain unknown. We aimed to identify which clinical factors are associated with morphometric brain changes in cognitively normal aging. METHODS: A cross-sectional study of 414 subjects, ≥50 years old submitted to clinical assessment and brain autopsy, after informed consent, was carried out at the São Paulo Autopsy Service, Brazil. Data on cognitive and functional evaluations were collected through structured interview applied to the next-of-kin. Brain weight (g) and volume (mL) measurements were obtained and adjusted for head circumference (cm). Associations between brain weight/volume and related factors were obtained through univariate and multivariate analysis. RESULTS: Participants were predominantly male (60.4%), Caucasian (69%), with mean age of 67.1 ± 10.9 years. Mean brain weight was 1219.2 ± 140.9 g, and mean brain volume was 1217.1 ± 152.3 mL. Head circumference was independently associated with low brain weight (p<0.001) and volume (p<0.001). Total and adjusted brain weight and volume decreased in some conditions. Female gender (p<0.001), hypertension (p<0.009), coronary artery disease (p<0.013) and walking assistance (p<0.011) were associated with lower adjusted brain weight while schooling was associated with higher adjusted brain weight (p<0.003). Female gender (p<0.001), age (p<0.001) and hypertension (p<0.011) were associated with low adjusted brain volume. CONCLUSION: Morphometric brain changes occur despite the absence of cognitive impairment and were predominantly associated with age, female gender, mobility impairment and cardiovascular conditions. Schooling may be a protective factor.

研究目的：认知功能损害（cognitive impairment）与脑重量及脑容积降低相关，而认知正常衰老人群脑形态学改变的相关影响因素仍未明确。本研究旨在明确认知正常衰老个体中，哪些临床因素与脑形态学改变存在关联。

研究方法：本研究为一项横断面研究（cross-sectional study），于巴西圣保罗尸检服务中心开展，共纳入414名50岁及以上的受试者。所有受试者签署知情同意书（informed consent）后，接受临床评估及脑部尸检（brain autopsy）。通过对受试者近亲（next-of-kin）开展结构化访谈，收集其认知与功能评估相关数据。测量脑重量（brain weight，单位：克）与脑容积（brain volume，单位：毫升），并对头围（head circumference，单位：厘米）进行校正。通过单变量分析（univariate analysis）与多变量分析（multivariate analysis），明确脑重量、脑容积与其相关影响因素之间的关联。

研究结果：受试者以男性为主（占比60.4%），白种人占69%，平均年龄为67.1±10.9岁。平均脑重量为1219.2±140.9g，平均脑容积为1217.1±152.3mL。头围与较低的脑重量（p<0.001）及脑容积（p<0.001）存在独立相关性。在部分临床状态下，校正后的总脑重量及脑容积有所下降。女性性别（p<0.001）、高血压（p<0.009）、冠状动脉疾病（p<0.013）及需辅助行走（p<0.011）与校正后的较低脑重量相关，而受教育程度与校正后的较高脑重量相关（p<0.003）。女性性别（p<0.001）、年龄（p<0.001）及高血压（p<0.011）与校正后的较低脑容积相关。

研究结论：即便无认知功能损害，认知正常衰老人群仍可出现脑形态学改变，其相关影响因素主要包括年龄、女性性别、运动功能受损及心血管疾病，而受教育程度或为其保护性因素。