Associations between Serum 25-hydroxyvitamin D, Sun Exposure Time, Dietary Vitamin D Intake, and New-Onset Acute Kidney Injury among 413,169 UK Adults.

ABSTRACT

BACKGROUND: The prospective associations of serum 25(OH)D, sun exposure time, and dietary vitamin D with risk of acute kidney injury (AKI) are unclear. OBJECTIVES: We aimed to evaluate the relations of serum 25(OH)D, sun exposure time, and dietary vitamin D intake with new-onset AKI and examine whether genetic susceptibility modified such associations. METHODS: A total of 413,169 participants (mean age was 56.4 y, 47.2% were male) from UK Biobank without prior AKI were included. Sun exposure time was expressed as time spent outdoors. Genetic risk scores were calculated by 263 single nucleotide polymorphisms, which showed significant associations with the estimated glomerular filtration rate. The primary outcome was new-onset AKI. Cox proportional hazards models were used to estimate the HRs and (95% CIs). RESULTS: During a median follow-up duration of 12 y, 16,938 (4.1%) participates developed new-onset AKI. Compared with those with serum 25(OH)D <25 nmol/L, significantly lower risks of new-onset AKI were found between participants with 25(OH)D 25 to <50 nmol/L (adjusted HR 0.76; 95% CI 0.73, 0.80), and ≥50 nmol/L (adjusted HR 0.69; 95% CI 0.65, 0.72). Moreover, in summer, participants who spent ≥4 h outdoors per day (tertile 3) had a significantly lower risk of new-onset AKI (adjusted HR 0.90; 95% CI 0.86, 0.95) than those who spent <2 h outdoors per day (tertile 1). Similar results were found for time spent outdoors in winter. In addition, those in quintile 5 of dietary vitamin D intake showed a lower risk of new-onset AKI (≥4.2 µg/d, adjusted HR 0.90; 95% CI 0.82, 0.98) than those in quintile 1 (<1.0 µg/d). Genetic risks of kidney diseases did not significantly modify all the 3 above associations (all P-interactions >0.05). CONCLUSIONS: Serum 25(OH)D concentrations, time spent outdoors, and dietary vitamin D intake were all inversely associated with new-onset AKI, independent of genetic risks for kidney diseases.