Abstract
Introduction: Despite the importance of vitamin D, the number of vitamin D-related research publications has declined since 2020. This study examines trends in vitamin D-related research and National Institutes of Health (NIH) funding over 4 decades. Methods: We conducted a PubMed search using medical subject headings terms to identify vitamin D-related papers published between 1985 and 2024. NIH funding data were from NIH Reporter; statistical significance was determined using negative binomial regression. Results: Vitamin D-related publications rose steadily from 1985 to 2000, surged from 2008 to 2021, peaked at 6,019 in 2021, and then declined. A similar trend was seen in research on vitamin D-associated diseases. NIH funding for vitamin D research peaked at $52.4 million in 2013 but decreased to $10.5 million by 2024. A negative binomial regression showed a significant difference in publication rates (P<.001) in Vitamin D-related publications with “year” being a significant predictor across all models (P<.05). Negative binomial regression across 4 decades showed an annual publication growth of Vitamin D-related papers of 1.44% (P=.002) from 1985 to 1994, 4.78% (P<.001) from 1995 to 2004, and 12.88% (P<.001) from 2005 to 2014. In contrast, during the years 2015 to 2024, the annual increase dropped to 0.63% (P=.389), indicating a decline in publication activity. Conclusions: Vitamin D research output surged through 2014 but has since lost momentum, declining from its 2021 peak and showing no significant annual growth from 2015 to 2024 (P=.389). These findings regarding vitamin D-related research raise important questions that remain unanswered.