Serum 25-hydroxyvitamin D levels and risk of overall and site-specific cancers in Korean adults: results from two prospective cohort studies.

BACKGROUND

The link between vitamin D and cancer remains inconclusive. In this study, we aimed to explore the relationship between circulating vitamin D levels and overall and site-specific cancers in Korean adults using data from two large prospective cohort studies.

METHODS

Baseline serum 25-hydroxyvitamin D [25(OH)D] levels were measured in a subset of participants from the Cardiovascular Disease Association Study (2005-2012) and the Health Examinees Study (2009-2013). We followed 46,514 adults aged ≥ 40 years who consented to linkage with national cancer registry data. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for cancer incidence according to quartiles of season-standardized 25(OH)D levels.

RESULTS

The median season-standardized 25(OH)D level was 45.6 nmol/L (interquartile range: 33.6-59.7 nmol/L). During the median follow-up of 10.6 years, 3,529 incident cancer cases were recorded. Compared with the first quartile, the upper quartiles of serum 25(OH)D were associated with a lower risk of overall cancer [HR (95% CI): 0.86 (0.77-0.95), 0.84 (0.75-0.93), and 0.80 (0.72-0.89), respectively; P for trend < 0.001]. For site-specific cancers, the HRs (95% CIs) for the comparison of extreme quartiles of serum 25(OH)D were 0.72 (0.52-0.99) for colorectal cancer, 0.32 (0.21-0.50) for liver cancer, and 0.75 (0.55-1.04) for lung cancer. Upon categorization of serum 25(OH)D levels based on absolute cut-off points, participants with levels ≥ 75 nmol/L had significantly lower risks of overall, liver, and lung cancers compared with those with levels < 30 nmol/L.

CONCLUSIONS

These findings suggest that higher 25(OH)D levels are associated with a lower risk of overall and some site-specific cancers in the Korean population.

CLINICAL TRIAL NUMBER

Not applicable.