Air pollution increases physical disability risk in older adults

By Dr. Priyom Bose, Ph.D.Reviewed by Benedette Cuffari, M.Sc.Sep 30 2024

Elevated serum magnesium levels are strongly linked to higher mortality in sepsis, suggesting a critical role for magnesium in assessing sepsis risk and guiding treatment strategies.

Study: Long-term air pollution exposure and incident physical disability in older US adults: a cohort study. Image Credit: DimaBerlin / Shutterstock.com

A recent Lancet Healthy Longevity study investigated the relationship between air pollutants and physical disability among older adults in the United States.

Physical disability and exposure to ambient air pollution

Physical disability is a key marker of overall health in older adults, with at least some degree of physical disability reported by about 40% of adults 65 years of age and older.

Exposure to nitrogen dioxide (NO₂), ozone (O₃), and ambient particulate matter is a known risk factor for premature mortality and morbidity. These pollutants induce inflammation and oxidative stress, associated with chronic diseases that can lead to disability later in life.

It remains unclear how exposure to air pollutants impacts the clinical manifestations of physical disabilities. Most studies examining the adverse effects of air pollutants have either been conducted in high-pollution settings or focused on single-pollutant models. There also remains a lack of studies conducted in lower-pollution settings. 

Furthermore, these studies are not suitable for inferring the independent effects of individual pollutants, as they often assess summary indicators as a single aggregate measure of multiple pollutants.

About the study

The current study explores the effects of air pollution on physical disability in a low-pollution setting. To this end, the researchers utilized multi-pollutant models to isolate the contribution of each pollutant and quantify any associations between physical disability and air pollution.

Data on incident activities of daily living (ADL) disability were collected from older individuals between 2000 and 2016. The analyzed air pollutants included fine particulate matter (PM_2.5), coarse particulate matter (PM_10–2⋅5), O₃, and NO₂, all of which are regulated by the U.S. Environmental Protection Agency (EPA).

The average NO₂, O₃, PM_2.5, and PM_10–2.5 concentrations at participants' residences were estimated as part of the Environmental Predictors of Cognitive Health and Aging study. A time-varying weighted Cox model was used to estimate hazard ratios (HRs) for incident physical disability.

Study findings

A total of 15,411 individuals with an average age of 70.2 years were considered in the analysis, 77% of whom were non-Hispanic Whites, 51% lived in suburban or rural areas, 83% owned their primary residence, and 55% were female. During the average follow-up period of about eight years, 48% of respondents developed an ADL disability.

Study participants with an ADL disability were exposed to slightly higher concentrations of air pollutants except O₃. This finding is similar to previous reports, in which a significant positive correlation was observed between PM_2.5 and NO₂, whereas a negative correlation was reported between NO₂ and O₃. A very weak or no correlation was noted between PM_10–2.5 and other pollutants.

Individuals residing in areas with higher concentrations of PM_2.5, PM_10–2.5, and NO₂ were at a greater risk of developing ADL disability; however, not all associations were significant. A lower rate of developing an ADL disability was associated with higher concentrations of O₃. The associations were robust for O₃ and PM_10–2.5 after adjusting for other pollutants.

The observed associations were similar when competing risks were considered, alternative models were used, and ADL disability data collected in the exit interviews were excluded. In a secondary analysis, individuals between 65 and 70 years of age, as well as those between 80 and 85 years of age, reported stronger associations for all four air pollutants than other age groups.

Conclusions

The current study identifies a higher risk of developing physical disability among older adults associated with exposure to air pollution; however, these results differed by the type of pollutant.

A key limitation of the study is the lack of considering whether the transition to ADL disability was temporary or permanent. Furthermore, some study participants could have improved after an initial event, which was not explored.

It is possible that exposure measurement error was present in the current analysis due to model fitting. Measurement error may have also been undetected due to the assumption that study participants resided at the same address prior to baseline contact when the address at baseline was unavailable. Another limitation of the current study is the lack of analysis of the biological mechanisms underlying these associations.