Elevated levels of air pollutants have been linked to bone damage in postmenopausal women, according to a new study led by scientists at Columbia University’s Mailman School of Public Health. The effects were most noticeable on the lumbar spine, where nitrous oxides damage the area twice as much as normal aging.
The research results appear in the peer-reviewed journal eClinicalMedicinePart of The Lancet Discovery Science open access journal series.
Previous studies of individual pollutants have suggested negative effects on bone mineral density, risk of osteoporosis and fractures in older people. The new study is the first to examine the link between air pollution and bone mineral density specifically in postmenopausal women, and the first to examine the effects of air pollution mixtures on bone outcomes.
Researchers analyzed data collected as part of the Women’s Health Initiative study of an ethnically diverse cohort of 161,808 postmenopausal women. They estimated exposure to air pollution (PM10, NO, NO2, and SO2) based on participants’ residential addresses. They measured bone mineral density (BMD; whole body, total hip, femoral neck, and lumbar spine) on admission at the first, third, and sixth year of follow-up using dual-energy X-ray absorptiometry.
The magnitude of the impact of nitric oxide on lumbar spine BMD would amount to an annual reduction of 1.22 percent – nearly double the annual impact of aging at each of the anatomical sites studied. These effects are thought to arise from the death of bone cells through oxidative damage and other mechanisms.
“Our results confirm that poor air quality can be a risk factor for bone loss, regardless of socioeconomic or demographic factors. The spine is one of the most vulnerable sites for this damage,” said study lead author Diddier Prada, MD, PhD, associate research scientist in the Department of Environmental Health Sciences at the Columbia Mailman School of Public Health.
“Improvements in exposure to air pollution, particularly nitrogen oxides, will reduce bone damage in postmenopausal women, prevent bone fractures and reduce health care costs associated with osteoporosis in postmenopausal women. Further efforts should focus on identifying those who are at higher risk of air pollution. bone damage,” says lead author Andrea Baccarelli, MD, PhD, chair of the Department of Environmental Health Sciences at the Columbia Mailman School of Public Health.
Car and truck exhaust are a major source of nitrogen oxides, as are emissions from power plants used to generate electricity.
Approximately 2.1 million osteoporosis-related fractures occur annually, resulting in annual direct healthcare costs of up to US$20.3 billion. Osteoporosis affects women more than men, with 80 percent of the estimated 10 million Americans with osteoporosis being women. Postmenopausal women are at higher risk, with one in two women over age 50 sustaining a fracture due to osteoporosis.
Previously, Columbia researchers had shown that long-term exposure to air pollution reduces BMD and increases the risk of fractures later in life. Subsequently, these results were confirmed in several human studies.
Study co-authors include Carolyn J. Crandall of UCLA; Allison Kupsco, Marianthi-Anna Kioumurtzoglou, Yike Shen, Gary Miller, Iuliana Ionita-Laza by Columbia Mailman; James D Stewart, Eric A Whitsel at UNC Chapel Hill; Duanping Liao and Jeff D. Yanosky of Public Health Sciences, Hershey, PA; Andrea Ramirez from the National Autonomous University of Mexico; and Jean Wactawski-Wende at SUNY Buffalo.
The research was supported by grants from the National Institutes of Health (ES030163, TR00187, ES020836, ES025225, ES009089, AG069120, ES032242, ES027747, ES031688, AG058704, ES028805, ES030616, ES029943).