Abstract

Background:

Dementia is a devastating neurologic condition that is common in older adults. We previously reviewed the epidemiological evidence examining the hypothesis that long-term exposure to air pollution affects dementia risk. Since then, the evidence base has expanded rapidly.

Objectives:

With this update, we collectively review new and previously identified epidemiological studies on air pollution and late-life cognitive health, highlighting new developments and critically discussing the merits of the evidence.

Methods:

Using a registered protocol (PROSPERO 2020 CRD42020152943), we updated our literature review to capture studies published through 31 December 2020, extracted data, and conducted a bias assessment.

Results:

We identified 66 papers (49 new) for inclusion in this review. Cognitive level remained the most commonly considered outcome, and particulate matter (PM) remained the most commonly considered air pollutant. Since our prior review, exposure estimation methods in this research have improved, and more papers have looked at cognitive change, neuroimaging, and incident cognitive impairment/dementia, though methodological concerns remain common. Many studies continue to rely on administrative records to ascertain dementia, have high potential for selection bias, and adjust for putative mediating factors in primary models. A subset of 35 studies met strict quality criteria. Although high-quality studies of fine particulate matter with aerodynamic diameter $\le 2.5\mathrm{\mu }\mathrm{m}$ (${\mathrm{PM}}_{2.5}$) and cognitive decline generally supported an adverse association, other findings related to ${\mathrm{PM}}_{2.5}$ and findings related to particulate matter with aerodynamic diameter $\le 10\mathrm{\mu }\mathrm{m}$ (${\mathrm{PM}}_{10}$, ${\mathrm{NO}}_2$, and ${\mathrm{NO}}_{\mathrm{x}}$) were inconclusive, and too few papers reported findings with ozone to comment on the likely direction of association. Notably, only a few findings on dementia were included for consideration on the basis of quality criteria.

Discussion:

Strong conclusions remain elusive, although the weight of the evidence suggests an adverse association between ${\mathrm{PM}}_{2.5}$ and cognitive decline. However, we note a continued need to confront methodological challenges in this line of research. https://doi.org/10.1289/EHP8716

中文翻译：

---

空气污染暴露与痴呆风险及相关结果：流行病学文献的最新系统回顾

摘要

背景：

痴呆症是一种破坏性的神经系统疾病，在老年人中很常见。我们之前回顾了流行病学证据，检验了长期暴露于空气污染会影响痴呆风险的假设。从那时起，证据基础迅速扩大。

目标：

通过本次更新，我们共同回顾了关于空气污染和晚年认知健康的新的和先前确定的流行病学研究，强调了新的发展并批判性地讨论了证据的优点。

方法：

使用注册方案 (PROSPERO 2020 CRD42020152943)，我们更新了文献综述以捕获截至 2020 年 12 月 31 日发表的研究、提取数据并进行偏倚评估。

结果：

我们确定了 66 篇论文（49 篇新论文）纳入本次综述。认知水平仍然是最常考虑的结果，颗粒物（PM）仍然是最常考虑的空气污染物。自我们之前的审查以来，本研究中的暴露估计方法已经得到改进，并且更多的论文着眼于认知变化、神经影像学和认知障碍/痴呆事件，尽管方法论问题仍然很常见。许多研究继续依赖行政记录来确定痴呆症，很可能存在选择偏差，并根据主要模型中的假定中介因素进行调整。其中 35 项研究符合严格的质量标准。尽管对具有空气动力学直径的细颗粒物进行了高质量的研究$\le 2.5\mathrm{\mu }\mathrm{米}$（${\mathrm{下午}}_{2.5}$）和认知能力下降通常支持不良关联，其他相关发现${\mathrm{下午}}_{2.5}$以及与空气动力学直径的颗粒物相关的发现$\le 10\mathrm{\mu }\mathrm{米}$（${\mathrm{下午}}_{10}$,${\mathrm{不}}_2$， 和${\mathrm{不}}_{\mathrm{X}}$）尚无定论，而且报道臭氧研究结果的论文太少，无法评论可能的关联方向。值得注意的是，只有少数有关痴呆症的发现被纳入根据质量标准进行考虑。

讨论：

尽管有大量证据表明两者之间存在负相关，但强有力的结论仍然难以捉摸。${\mathrm{下午}}_{2.5}$和认知能力下降。然而，我们注意到在这一领域的研究中仍然需要面对方法论的挑战。https://doi.org/10.1289/EHP8716