Association of indoor air pollution on cognitive dysfunction among elderly

Cognitive dysfunction among the elderly is a devastating condition preceded by accumulation of neuropathology leading to accelerated cognitive decline. Many epidemiologic studies have reported the relation between indoor air pollution exposure and cognitive impairment. To clarify the nature of the association, a comprehensive systematic review and meta-analysis were performed.

The analysis included all observational studies, including cross-sectional studies, prospective and retrospective cohort studies. Experimental studies, randomized controlled trials (RCTs), and controlled clinical trials were excluded. Studies on the relationships of indoor air pollution and cognition published before 30 April 2021 which are peer-reviewed scientific publications available in English were included after performing a structured literature search through electronic databases, including PubMed, Embase, Cochrane Library, and clinical trial.gov. A total of 146 articles were collected, and after screening thoroughly only, 9 studies were selected. Meta-analysis for the final set of selected studies was performed using the R software.

The quality of all the studies was adequate as almost all reported an association between at least one pollutant and cognitive dysfunction. However, relatively few studies considered outcomes that provide the most substantial evidence for a causal effect. In total, 5 studies have reported on cognitive function. The pooled mean of cognitive function was 12.16 (95% CI: 10.73 to 13.58). However, the heterogeneity was very high (I2=100%; chi-square test for heterogeneity = p<0.001). We used a modified JBI structured risk of the bias assessment tool, and it was minimal among the included studies as most of the studies have followed a random sampling method and explicitly mention it in their methods.

Exposure to indoor air pollution through fuels used for cooking and heating was significantly associated with cognitive dysfunction among elderly women. Given the limitations, a more extensive meta-analysis and longitudinal studies are recommended to investigate the biological mechanism behind the impact of indoor air pollution on cognitive health.