My hypothesis is that COVID-19 is more severe because of a Vitamin D deficiency and old people are more likely to be deficient. The discussion section referenc

My hypothesis is that COVID-19 is more severe because of a Vitamin D deficiency and old people are more likely to be deficient. The discussion section references a study from 2017 which shows Vitamin D's helps protect against acute respiratory infections, especially those who are D deficient. It mentions the countries with lower levels of vitamin D and higher mortality rates (Spain, Italy, Switzerland) also have an older population. On a different topic: Vitamin D has been touted as this miracle vitamin but studies and trials have shown that it's not effective for improving cardiovascular health or bone density.