Xinye Qiu, PhD

An association was identified between long-term air pollution exposure and a raised depression diagnosis risk later in life for US Medicare enrollees, according to new findings.¹

Their research was conducted to assess the relationship between long-term exposure to air pollution and older adults’ potentially higher risk of late-onset depression diagnosis.

This study was authored by Xinye Qiu, PhD, from the Department of Environmental Health at the Harvard T.H. Chan School of Public Health.

“While the evidence for acute and cross-sectional associations has increased in recent years, high-quality evidence looking at late-onset depression in long-term prospective longitudinal cohorts is lacking,” Qiu and colleagues wrote. “To our knowledge, this study is the first to examine the associations between long-term exposure to air pollution and risk of late-onset depression incidence among the US older adult population…over a study period of more than 10 years.”

Research and Methods

The investigators used a longitudinal, cohort study that is population-based, recruiting participants known to be enrollees in US Medicare aged 64 years-or-older.

The team also collected the necessary data from the US Centers for Medicare and Medicaid Services Chronic Conditions Warehouse, with the older adult participant population having been enrolled in both Medicare Part A and Part B and the Medicare Fee-for-Service program.

The research team assessed long-term exposure of those in residential areas to 3 major pollutants: parts of nitrogen dioxide per billion (NO2), micrograms of fine particulate matter per cubic meter (PM2.5), and parts of ozone per billion (O3).

The primary measures being analyzed in the study involved finding depression diagnosis information through Medicare claims, finding dates of first depression occurrences, stratifying percentage changes in depression risk and hazard ratios, determining the environmental factors of participants’ neighborhoods, and identifying socioeconomic factors and healthcare access for participants.

The ended up recruiting 8,907,422 Medicare enrollees from 2005 to 2016, and the analyses of these study participants’ data spanned from March to November of 2022. Of these 8,907,422 participants, there ended up being 1,526,690 later-onset depression diagnoses reported in total.

Study Results

Among the 8,907,422 study participants recruited for the study, around 57% were female and about 90% of the participants were reported as being White.

The investigators concluded that associations were found, noting that for every 5-unit rise in long-term mean exposure to each of the 3 pollutants in their tri-pollutant study model, there was an adjusted percentage rise in risk for depression.

They added that there was an adjusted risk increase of 0.91% (95% CI, 0.02% to 1.81%) for PM2.5, 0.61% (95% CI, 0.31% to 0.92%) for NO2, and 2.13% (95% CI, 1.63% to 2.64%) for O3.

The research team’s subgroup analysis indicated that greater associations with NO2 and PM2.5 and depression were found to be among those who were more disadvantaged socioeconomically.

They also noted a greater sensitivity to NO2 for participants who had cardiovascular disease, as well as metabolic, respiratory, or neurological comorbidities.

“In this cohort study among US nationwide Medicare enrollees over the study period, we observed statistically significant harmful associations between long-term exposure to elevated levels of air pollution and increased risk of late-life depression diagnosis,” they wrote.

The investigators added their findings have both environmental regulation and public health management implications.

References:

1. Qiu X, Shi L, Kubzansky LD, et al. Association of Long-term Exposure to Air Pollution With Late-Life Depression in Older Adults in the US. JAMA Netw Open. 2023;6(2):e2253668. doi:10.1001/jamanetworkopen.2022.53668