A new research in the Oxford Economic Papers shows that migration movements from regions of high sunlight to regions of low sunlight have affected current health outcomes in destination countries over the past 500 years.
Researchers also found that the ability of people to synthesize vitamin D from sunlight decreases with skin pigmentation, and that vitamin D deficiency is directly related to a higher risk of mortality, including cardiovascular disease, type 1 and type 2 diabetes, hypertension, and some cancers. Latest research also shows that the severity of COVID-19 is impaired by vitamin D.
Researchers concentrated on groups from regions with high solar radiation that moved between 1500 and today to regions with low solar radiation.
The resulting demographic changes have triggered a major increase in the risk of vitamin D deficiency.
Over a long historical period, the researchers analyzed the aggregate health effects of such migration.
For this, the researchers produced a measure that showed the risk in a given population of vitamin D deficiency.
The measure tracked the difference between the intensity of sunlight at the ancestral place of residence of the population and the real intensity of sunlight at the current place of residence.
The researchers then explored its explanatory power in relation to life expectancy worldwide, using the disparity between ancestral and ambient sunlight as a measure of the possible risk of vitamin D deficiency. The researchers found that life expectancy was negatively associated with a higher risk of vitamin D deficiency, with all else being equal.
The researchers pointed out that the adverse effects of prolonged sun exposure are now well established, leading individuals to try to avoid sunburn through strategies such as sunscreen and restricted time outdoors.
Efficient skin cancer therapies are widely available as well. People now spend more time indoors, which limits their exposure to sunshine, than their ancient ancestors.
Consequently, since ancient times, the risk of premature death from prolonged sun exposure has declined.
Lower exposure to sunlight, however, increases the risk of vitamin D deficiency, especially in people with higher skin pigmentation whose ancestors came from regions with high exposure to sunlight.
Ultimately, the researchers concluded here that a migration-driven disparity between skin pigmentation strength and ambient sunlight can both be related to contemporary inequalities in global health and explain them. In the absence of such migration flows, low-sunlight regions which have undergone high immigration from high-sunlight regions have lower life expectancy than would have been the case.
This study is significant because the correlation between increased risk of vitamin D deficiency and differences in life expectancy between countries and regions is the first to be reported.
It thus underlines the potentially large benefit of taking vitamin D supplements, especially in the fall and winter, in terms of additional years of life, says author Dr.
Thomas Andersen Barnebeck.
Reference: 7 January 2021, Economic Papers of Oxford.