Uncertainty exists regarding the relation of body size and weight change with dementia risk. As populations continue to age and the global obesity epidemic shows no sign of waning, reliable quantification of such associations is important. We examined the relationship of body mass index, waist circumference, and annual percent weight change with risk of dementia and its subtypes by pooling data from 19 prospective cohort studies and four clinical trials using meta‐analysis. Compared with body mass index–defined lower‐normal weight (18.5‐22.4 kg/m²), the risk of all‐cause dementia was higher among underweight individuals but lower among those with upper‐normal (22.5‐24.9 kg/m²) levels. Obesity was associated with higher risk in vascular dementia. Similarly, relative to the lowest fifth of waist circumference, those in the highest fifth had nonsignificant higher vascular dementia risk. Weight loss was associated with higher all‐cause dementia risk relative to weight maintenance. Weight gain was weakly associated with higher vascular dementia risk. The relationship between body size, weight change, and dementia is complex and exhibits non‐linear associations depending on dementia subtype under scrutiny. Weight loss was associated with an elevated risk most likely due to reverse causality and/or pathophysiological changes in the brain, although the latter remains speculative.

中文翻译：

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人体测量学和体重变化与痴呆及其主要亚型风险的关联：一项包含 280 万成年人和 57 294 例痴呆病例的荟萃分析。


体型和体重变化与痴呆风险的关系存在不确定性。随着人口持续老龄化和全球肥胖流行没有减弱的迹象，对这种关联进行可靠的量化非常重要。我们通过荟萃分析汇集 19 项前瞻性队列研究和 4 项临床试验的数据，研究了体重指数、腰围和年度体重变化百分比与痴呆及其亚型风险的关系。与体重指数定义的正常体重下限（18.5-22.4 kg/m ² ）相比，体重不足的个体患全因痴呆的风险较高，但体重正常上限（22.5-24.9 kg/m ² ）的个体患全因痴呆的风险较低水平。肥胖与血管性痴呆的较高风险相关。同样，相对于腰围最低的五分之一的人，腰围最高的五分之一的人患血管性痴呆的风险没有显着升高。相对于体重维持，体重减轻与更高的全因痴呆风险相关。体重增加与较高的血管性痴呆风险关联较弱。身体尺寸、体重变化和痴呆之间的关系很复杂，并且根据仔细观察的痴呆亚型表现出非线性关联。体重减轻与风险升高相关，很可能是由于反向因果关系和/或大脑的病理生理变化所致，尽管后者仍然是推测性的。