Association between shift work and biological factors including FGF-23, klotho, and serum 25-(OH) vitamin D3 among Korean firefighters: a cross-sectional study

Abstract

Study Objectives: Shift work is known to be detrimental to an individual's health as it disrupts the circadian rhythm and is a risk factor for cancer. It has been reported that elevated fibroblast growth factor (FGF)-23, increased serum soluble alpha-klotho, and decreased vitamin D-3 are associated with cancer progression. We studied the relationship between shift work and the levels of FGF-23, alpha-klotho, and vitamin D-3 amongst firefighters, as they work in long shifts outside the traditional daytime schedule. Methods: The study consisted of 450 participants who were firefighters. We measured FGF-23, alpha-klotho, and vitamin D-3 levels in their blood and a set of questionnaires were given to the participants to evaluate their health habits. After determining and adjusting for potential confounding factors, we compared the levels of FGF-23, alpha-ldotho, and serum vitamin D-3 by job and shift types. Results: FGF-23 and alpha-klotho levels were significantly higher in shift workers than traditional day workers, and in 3-day cycle shift workers than workers with another shift schedule. When the levels of these substances were compared based on different types of jobs, firefighters had a lower level of vitamin D-3. We conclude that shift work is positively correlated with the levels of FGF-23 and alpha-klotho. Conclusions: Levels of FGF-23 and alpha-klotho were linked to shift work and job types. Although vitamin levels did not differ by shift types, vitamin D-3 levels were lower in firefighters. These findings suggest that high levels of FGF-23 and alpha-klotho are potential risk factors for cancer among firefighters.