Early Pandemic Associations of Latitude, Sunshine Duration, and Vitamin D Status with COVID-19 Incidence and Fatalities: A Global Analysis of 187 Countries

In the face of the COVID-19 pandemic, understanding the interplay between environmental factors and virus spread is crucial for global preparedness strategies. This study explores how geographic latitude, sunshine duration, and vitamin D status were associated with the incidence and fatality rates of COVID-19 across 187 countries during the crucial early months of the outbreak. Data on the total number of COVID-19 cases by country were obtained from the United Nations database as of June 30, 2020. Univariate and multivariate regression analyses were conducted to determine the associations between COVID-19 cases and latitude, average hours of sunshine from January to June, and mean 25-hydroxyvitamin D (25(OH)D) levels. The average COVID-19 prevalence and mortality per million population were 2,087 and 69, respectively, with a case fatality rate of 3.19%. COVID-19 case fatality rate was positively associated with latitude (β = 0.030; 95% CI: 0.008, 0.052) and negatively associated with hours of sunshine (β = -1.51; 95% CI: -4.44, 1.41) and 25(OH)D levels (β = - 0.054; 95% CI: -0.089, -0.019) in adjusted regression analyses. Findings were similar for COVID-19 prevalence and mortality rate. These findings indicate that higher latitude and lower 25(OH)D levels was associated with increased COVID-19 severity and mortality.

While the data highlight potential links between vitamin D status and COVID-19 outcomes, causality cannot be inferred. Further research, including large-scale, well-controlled trials, is essential to determine whether vitamin D plays a definitive role in COVID-19 prevention and management.