Department of Epidemiology, Harvard TH Chan School of Public Health, Boston, MA, USA.
Department of Environmental Heath, Harvard TH Chan School of Public Health, Boston, MA, USA.
BMJ. 2023 Apr 5;381:e071620. doi: 10.1136/bmj-2022-071620.
To investigate the role of air pollutants in risk of dementia, considering differences by study factors that could influence findings.
Systematic review and meta-analysis.
EMBASE, PubMed, Web of Science, Psycinfo, and OVID Medline from database inception through July 2022.
Studies that included adults (≥18 years), a longitudinal follow-up, considered US Environmental Protection Agency criteria air pollutants and proxies of traffic pollution, averaged exposure over a year or more, and reported associations between ambient pollutants and clinical dementia. Two authors independently extracted data using a predefined data extraction form and assessed risk of bias using the Risk of Bias In Non-randomised Studies of Exposures (ROBINS-E) tool. A meta-analysis with Knapp-Hartung standard errors was done when at least three studies for a given pollutant used comparable approaches.
2080 records identified 51 studies for inclusion. Most studies were at high risk of bias, although in many cases bias was towards the null. 14 studies could be meta-analysed for particulate matter <2.5 µm in diameter (PM). The overall hazard ratio per 2 μg/m PM was 1.04 (95% confidence interval 0.99 to 1.09). The hazard ratio among seven studies that used active case ascertainment was 1.42 (1.00 to 2.02) and among seven studies that used passive case ascertainment was 1.03 (0.98 to 1.07). The overall hazard ratio per 10 μg/m nitrogen dioxide was 1.02 ((0.98 to 1.06); nine studies) and per 10 μg/m nitrogen oxide was 1.05 ((0.98 to 1.13); five studies). Ozone had no clear association with dementia (hazard ratio per 5 μg/m was 1.00 (0.98 to 1.05); four studies).
PM might be a risk factor for dementia, as well as nitrogen dioxide and nitrogen oxide, although with more limited data. The meta-analysed hazard ratios are subject to limitations that require interpretation with caution. Outcome ascertainment approaches differ across studies and each exposure assessment approach likely is only a proxy for causally relevant exposure in relation to clinical dementia outcomes. Studies that evaluate critical periods of exposure and pollutants other than PM, and studies that actively assess all participants for outcomes are needed. Nonetheless, our results can provide current best estimates for use in burden of disease and regulatory setting efforts.
PROSPERO CRD42021277083.
探讨空气污染物在痴呆风险中的作用，同时考虑到可能影响研究结果的研究因素差异。
系统评价和荟萃分析。
EMBASE、PubMed、Web of Science、Psycinfo 和 OVID Medline 从数据库成立到 2022 年 7 月。
纳入研究包括成年人（≥18 岁）、纵向随访、考虑美国环境保护署的空气污染物标准和交通污染的代表物、平均暴露时间超过一年且报告了环境污染物与临床痴呆之间的关联。两位作者使用预定义的数据提取表格独立提取数据，并使用非随机暴露研究中的风险偏倚 (ROBINS-E) 工具评估风险偏倚。当给定污染物有至少三项研究使用可比方法时，采用具有 Knapp-Hartung 标准误差的荟萃分析。
确定了 2080 条记录，其中包括 51 项研究。大多数研究存在高偏倚风险，但在许多情况下，偏倚偏向于零。对于直径小于 2.5 µm 的颗粒物 (PM)，有 14 项研究可以进行荟萃分析。每增加 2 μg/m 的 PM，风险比为 1.04（95%置信区间 0.99 至 1.09）。在使用主动病例确定的 7 项研究中，风险比为 1.42（1.00 至 2.02），在使用被动病例确定的 7 项研究中，风险比为 1.03（0.98 至 1.07）。每增加 10 μg/m 的二氧化氮的风险比为 1.02（0.98 至 1.06）（9 项研究），每增加 10 μg/m 的氮氧化物的风险比为 1.05（0.98 至 1.13）（5 项研究）。臭氧与痴呆症无明显关联（每增加 5 μg/m 的风险比为 1.00（0.98 至 1.05）；4 项研究）。
PM 可能是痴呆症的一个危险因素，此外还有二氧化氮和氮氧化物，但数据更为有限。荟萃分析的风险比受到限制，需要谨慎解释。研究之间的结果确定方法不同，每种暴露评估方法可能只是与临床痴呆结果相关的因果相关暴露的代表。需要评估暴露的关键时期和除 PM 以外的污染物的研究，以及积极评估所有参与者结局的研究。尽管如此，我们的结果可以为疾病负担和监管环境中的研究提供当前最佳估计值。
PROSPERO CRD42021277083。
