Nonsmokers exposed to secondhand cigarette smoke are at increased risk of chronic kidney disease (CKD), according to new study findings published in the Clinical Journal of the American Society of Nephrology.

The study included 131,196 never-smokers with normal kidney function who participated in the Korean Genome and Epidemiology Study from 2001 to 2014 (mean age 53 years; 75% women). Investigators classified patients into 3 groups based on the frequency of secondhand smoke exposure: no exposure, less than 3 days per week, and 3 or more days per week. In these groups, 1.8%, 1.7%, and 2.0%, respectively, had CKD. Individuals with less than 3 days and 3 days or more of exposure had significant 72% and 44% greater odds of prevalent CKD than the no-exposure group, Jong Hyun Jhee, MD, of Inha University in Korea, and colleagues reported.

The investigators also examined the risk of incident CKD development in a longitudinal cohort of 1948 participants without CKD at baseline. The individuals were a subset of the main cohort.

CKD developed in 319 participants over a mean follow-up period of 104 months. On multivariable analysis, individuals with less than 3 days and 3 days or more of exposure to secondhand smoke had significant 59% and 66% greater odds of CKD, respectively, compared with the no-exposure group.

Secondhand smoke increases CKD risk to a comparable degree as firsthand smoke, according to the researchers.

“These findings suggest that the association of CKD with secondhand smoke exposure could be at least similar to its relationship with active smoking,” Dr Jhee’s team stated. “Although active smoking is an intermittent activity, nonsmokers are commonly exposed to secondhand smoke from multiple smokers. Therefore, some nonsmokers exposed to secondhand smoke could be exposed to a similar dose of cigarette smoke to active smokers.”

With respect to possible mechanisms, smoke may inflame the lungs and spur oxidative stress, ultimately affecting the entire circulation, including the kidneys, the team said. They also cited a recent study suggesting nicotine may cause apoptosis of podocytes.

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Jhee JH, Joo YS, Kee YK, et al. Secondhand smoke and CKD. Clin J Am Soc Nephrol. March 2019, CJN.09540818; DOI:10.2215/CJN.09540818