Trinity researchers at the Irish Longitudinal Study on Ageing (TILDA) have collaborated with the University of Liverpool on some new findings regarding the variation in how Covid-19 affects people.
The study has found that the proportion of older people in each country greatly affected that country’s Covid-19 mortality rates. After adjusting for this, a strong association remains across the Northern hemisphere between more northerly latitude and higher death rates from Covid-19.
The positive correlation between Covid-19 mortality and latitude exists above 28 degrees. Beyond 35 degrees, human populations often have insufficient ultraviolet B exposure. This causes problems for the maintenance of Vitamin D levels in the blood throughout winter and spring.
Vitamin D is known to have a variety of health benefits including boosting the body’s immune response, supporting bone and muscle health and in playing a potentially critical role in suppression of the severe pro-inflammatory response.
Evidence linking vitamin D deficiency with Covid-19 severity is only circumstantial, but it is growing. Researchers point out that if the association between vitamin D deficiency and Covid-19 severity is causative, then the disease should prove seasonal, since more severely affected individuals are infectious for longer.
Professor Rose Anne Kenny, Principal Investigator of TILDA and author of the study said: “Our group is cautious about ascribing a causal association in advance of results from Vitamin D supplementation studies which are on-going. However, given the high prevalence of Vitamin D deficiency in many northern latitude countries, the reduction in outdoor physical activity during Covid, and the safety of Vitamin D, public health bodies in Ireland and UK are recommending that older persons, those who are mainly indoors and those from other high risk groups such as BAME, should take regular supplements.”
Professor Jon Rhodes, Emeritus Professor of Medicine, University of Liverpool and co-author of the study said: “Vitamin D is an unusual vitamin – it is a hormone and we get most of it by the action of ultraviolet light on cholesterol in the skin. Unless you live in a sunny country or eat a very large amount of oily fish you are quite likely to need supplements to maintain a normal level. It is plausible that vitamin D deficiency increases risk of severe Covid-19 illness, but all the evidence is indirect. The correlation between Covid-19 mortality and northern latitude, with consequently reduced ultraviolet exposure from sunlight, adds to this evidence.”