Background: Weight loss is a common phenomenon among the elderly and is identified as an important indicator of health status. Many epidemiology studies have investigated the association between weight loss and dementia, but the results were inconsistent.

Objective: To examine and determine the association between weight loss and the risk of dementia.

Methods: Eligible cohort studies involving weight loss and dementia were searched from PubMed, Embase, and Ovid databases through October 2018. Pooled relative risks (RRs) with its 95% confidence intervals (CIs) were used to estimate the effects of weight loss on the risk of dementia. Subgroup and sensitivity analyses were performed to explore the potential sources of heterogeneity. The Begg’s test and Egger’s test were used to assess the publication bias.

Results: A total of 20 cohort studies with 38,141 participants were included in this meta-analysis. Weight loss was significantly associated with the risk of dementia (RR=1.26, 95% CI=1.15-1.38). BMI decline ≥0.8 units (RR=1.31, 95% CI=1.10-1.56) and ≥4% (RR=1.19, 95% CI=1.03-1.38) could increase the risk of dementia. The risk of all-cause dementia for people with weight loss increased by 31% (RR=1.31, 95% CI=1.15-1.49), and 25% higher for incident Alzheimer’s disease (RR=1.25, 95% CI=1.07-1.46). Weight loss in participants with normal weight had a similar dementia risk (RR=1.21, 95% CI=1.06-1.38) with the overweight individuals (RR=1.22, 95% CI=1.11-1.34).

Conclusion: Weight loss may be associated with an increased risk of dementia, especially for Alzheimer's disease. Maintaining weight stability may help prevent dementia.

背景：体重减轻是老年人的普遍现象，被确定为健康状况的重要指标。许多流行病学研究调查了体重减轻与痴呆之间的关联，但结果并不一致。

目的：检查和确定体重减轻与痴呆风险之间的关联。

方法：从 PubMed、Embase 和 Ovid 数据库中搜索到 2018 年 10 月的涉及体重减轻和痴呆症的符合条件的队列研究。使用汇总相对风险 (RR) 及其 95% 置信区间 (CI) 来估计体重减轻对痴呆症的风险。进行亚组分析和敏感性分析以探索异质性的潜在来源。Begg 检验和 Egger 检验用于评估发表偏倚。

结果：本荟萃分析共纳入了 20 项队列研究，共有 38,141 名参与者。体重减轻与痴呆风险显着相关（RR=1.26，95% CI=1.15-1.38）。BMI 下降≥0.8 个单位（RR=1.31，95% CI=1.10-1.56）和≥4%（RR=1.19，95% CI=1.03-1.38）可能会增加痴呆的风险。体重减轻的人患全因痴呆的风险增加了 31% (RR=1.31, 95% CI=1.15-1.49)，阿尔茨海默病的发生风险增加了 25% (RR=1.25, 95% CI=1.07-1.46) ）。体重正常的参与者体重减轻与超重个体（RR=1.22，95% CI=1.11-1.34）具有相似的痴呆风险（RR=1.21，95% CI=1.06-1.38）。

结论：体重减轻可能与痴呆风险增加有关，尤其是阿尔茨海默病。保持体重稳定可能有助于预防痴呆症。