Long-term exposure to common levels of air pollution may be linked to an increased risk of depression after age 64, according to a study published today in JAMA Network Open.
“Although depression is less prevalent among older adults as compared with the younger population, there can be serious consequences, such as cognitive impairment, comorbid physical illness, and death,” wrote Xinye Qiu, Ph.D., of the Harvard T.H. Chan School of Public Health and colleagues. “Therefore, it is of crucial importance to study preventable risk factors for developing depression among older adults to reduce the associated health care burden.”
Qiu and colleagues conducted a longitudinal cohort study using data from all Medicare beneficiaries who were continuously enrolled in the Medicare Fee-for-Service program and Medicare Part A and Part B from 2000 to 2016. The researchers excluded any participants who received a depression diagnosis within five years of Medicare enrollment to reduce the occurrence of participants with preexisting depression. Depression was identified based on all available Medicare claims, including those from a hospital or skilled nursing facility. Finally, the authors looked at three air pollutants: fine particulate matter (measured in micrograms per cubic meter), nitrogen dioxide (measured in parts per billion), and ozone (measured in parts per billion). They used ZIP codes included in the Medicare data to track air pollution exposure for each year of the study period as well as the five years before to determine long-term exposure.
The final study sample included over 8.9 million Medicare beneficiaries (mean age of 73.7 years) and 1.5 million late-life depression diagnoses. All three air pollutants included in the study were associated with an increased risk of developing depression after 64 years of age. Each five-unit increase in long-term exposure to particulate matter, nitrogen dioxide, and ozone was associated with an adjusted percentage increase in depression risk of 0.91%, 0.61%, and 2.13%, respectively.
The authors found that older adults with comorbidities had a higher risk of developing late-life depression when exposed to elevated pollution, especially nitrogen dioxide, compared with those without comorbidities. Further, the authors found that socioeconomically disadvantaged participants (those who also qualified for Medicaid) had a higher risk of late-life depression when exposed to particulate matter or nitrogen dioxide.
“The study findings have implications for both environmental regulation and public health management,” the authors concluded. “We hope this study can inspire researchers to further consider possible environmental risk factors (such as air pollution and living environment) for the prevention of geriatric depression, to understand the disease better moving forward, and to improve the delivery of mental health care services among older adults.”
For related information, see the American Journal of Psychiatry article “Association Between Ambient Air Pollution and Daily Hospital Admissions for Depression in 75 Chinese Cities.”
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