Seasonal variation of idiopathic benign paroxysmal positional vertigo correlates with serum 25-hydroxyvitamin D levels: a six-year registry study in Shanghai, China

Seasonal variation of benign paroxysmal positional vertigo (BPPV) occurrence has been reported in recent years. Whether the seasonality of BPPV also exists in Chinese patients and whether it correlates with serum vitamin D levels is unexplored. We retrospectively analyzed the data of 1269 new-onset idiopathic BPPV patients registered in our vertigo outpatient clinic over a six-year period. Additionally, serum 25-hydroxyvitamin D levels during this period were measured in 877 patients by chemiluminescence immunoassay. We delineated the changing trend of the monthly BPPV patient numbers and serum 25-hydroxyvitamin D levels, and the correlation between them was explored. December to next March is the top 4 months with higher BPPV patient numbers. The median BPPV patient numbers in winter group were higher than those in summer group (20 vs. 16 patients, p < 0.05). Median 25-hydroxyvitamin D levels in winter group were much lower than those in summer group (16.3 vs. 20.8 ng/ml, p < 0.001) and autumn group (16.3 vs. 19.3 ng/ml, p < 0.05). A moderate negative correlation was observed between median serum 25-hydroxyvitamin D levels and BPPV patient numbers each month. The onset of BPPV also shows a seasonal fluctuation in Chinese patients. This phenomenon may be related to serum vitamin D levels.