Serum levels of club (Clara) cell secretory protein predict cancer mortality in adults

Background— Club (formerly Clara) cell secretory protein (CC16) is produced mainly by bronchiolar club cells and has been shown to have protective effects against airway inflammation and oxidative stress from cigarette smoking and related carcinogens. The goal of this study was to determine whether serum CC16 levels predict all-cause and cancer-specific mortality in adults. Methods— We used data from the population-based TESAOD study, a prospective cohort study of respiratory health initiated in Tucson, AZ in 1972. At baseline, participants completed standardized respiratory questionnaires and lung function tests. Serum CC16 was measured in cryopreserved serum samples. A review of vital status of participants as of January 1 st , 2011 was completed through contact with next of kin, collection of death certificates, and linkage with the National Death Index. Findings— A total of 1086 participants who were 21 to 70 years old at enrollment were included. Of these, 653 (60%) died by 2011 and cause of death was ascertained for 649 (99%). In Cox proportional hazards models adjusted for sex, age, education, body mass index categories, smoking and pack-years, and baseline levels of lung function, serum CC16 levels at the baseline survey were inversely associated with mortality risk over the study follow-up. Mortality risk increased by 16% for each standard deviation (SD) decrease in CC16 (Hazard Ratio (HR), 95% CI: 1.16, 1.06 – 1.26; p = 0.0007). When data on cause-specific mortality were analyzed, each SD decrease in serum CC16 was associated with >40% increased risk of dying of cancer (adjusted