Wildfire Air Pollution Exacerbates Atopic Dermatitis and Itch in Older Adults

The skin of older adults has a greater vulnerability to air pollution, with rapid outcomes after short-term exposure to air pollution.

Rates of clinic visits for atopic dermatitis (AD) and itch were significantly increased among adults at least 65 years of age exposed to short-term air pollution from a California wildfire, according to study findings in a research letter published in JAMA Network Open.

Researchers sought to investigate if adults at least 65 years of age would be at greater risk than younger adults for skin exacerbations related to wildfire pollution exposure.

They conducted a cross-sectional study at an academic medical center in San Francisco, California from October 2018 to February 2019 (during the California Camp Fire) and from October 2015 to February 2016 (control, no fire), and from October 2016 to February 2017 (control, no fire). Assessed adult patients had 5529 visits for AD and 1319 for itch (3448 unique patients; 67.4% women; 44.6±21.1 years of age). The California Camp Fire (approximately 175 miles from San Francisco) resulted in a 9-fold increase in weekly mean particulate matter concentrations in the city from November 8 to 21, 2018.

Researchers collected data stratified by age, 18 to 64 or at least 65 years. They used Poisson regression to analyze data, and statistical models were adjusted for humidity, temperature, holiday, year, and overall patient volume at clinics.

The increased association of risk for pollution-induced skin exacerbations with older age may be due to age-related molecular processes affecting skin barrier function.

The adjusted rate of clinic visits observed by researchers for adults 18 to 64 years of age for AD during a wildfire week was 1.1 (95% CI, 1.0-1.3) times the rate for weeks without a wildfire for a 0-week lag. This adjusted rate for adults at least 65 years of age was 1.4 (95% CI, 1.1-1.9) times. They found a mean weekly 1-unit increase in smoke plume density associated with a 1.3 (95% CI, 1.1-1.6) times higher rate of clinic visits for AD for adults at least 65 years of age and a 1.2 (95% CI, 1.1-1.3) times higher rate for adults 18 to 64 years of age for a 0-week lag.

Researchers found the adjusted rate of clinic visits for itch during a wildfire week for adults 18 to 64 years of age was 1.1 (95% CI, 0.8-1.7) times the rate for weeks without a wildfire for a 0-week lag. This adjusted rate for adults at least 65 years of age was 1.6 (95% CI, 1.1-2.5) times.

They observed a mean weekly 1-unit increase in smoke plume density score associated with a 1.4 (95% CI, 1.1-1.9) times higher rate of clinic visits for itch for adults at least 65 years of age but no change in the rate of clinic visits among adults 18 to 64 years of age for itch (rate ratio 1.0 [95% CI, 0.8-1.4]). They noted similar results for the particulate matter with diameters 2.5 μm or smaller.

Study limitations include results of only 1 wildfire examined which limited generalizability, and no patients from primary care clinics were included in analysis.

Researchers concluded “the skin of older adults has a greater vulnerability to air pollution, with rapid outcomes after short-term exposure to air pollution.” They added “The increased association of risk for pollution-induced skin exacerbations with older age may be due to age-related molecular processes affecting skin barrier function.” Severe itching in adults at least 65 years of age may have multiple causes and air pollution may be among them. They urge clinical counseling and public health education targeting adults at least 65 years of age in areas affected by wildfires concerning the association of skin health with air pollution.

References:

Fadadu RP, Green M, Jewell NP, Grimes B, Vargo J, Wei ML. Association of exposure to wildfire air pollution with exacerbations of atopic dermatitis and itch among older adults. JAMA Netw Open. October 3, 2022;5(10):e2238594. doi:10.1001/jamanetworkopen.2022.38594