Winter vs summer in US – 25 percent more deaths, 16 percent less vitamin D – Oct 2017

Seasonal variations of U.S. mortality rates: Roles of solar ultraviolet-B doses, vitamin D, gene exp ression, and infections

The Journal of Steroid Biochemistry and Molecular Biology, Volume 173, October 2017, Pages 5-12, https://doi.org/10.1016/j.jsbmb.2017.01.003
William B.Grant a Harjit Pal Bhatto ab Barbara J.Boucher c

Highlights
• Death rates vary seasonally with lowest rates in summer.
• Circulatory and respiratory system diseases vary seasonally.
• The primary factor proposed is variations in solar UVB.
• Increased infections near the start of school raise rates.
• Vitamin D concentrations >36 ng/mL are recommended.

Free, fuzzy image from the web

Death rates in the U.S. show a pronounced seasonality. The broad seasonal variation shows about 25% higher death rates in winter than in summer with an additional few percent increase associated with the Christmas and New Year’s holidays. A pronounced increase in death rates also starts in mid-September, shortly after the school year begins. The causes of death with large contributions to the observed seasonality include diseases of the circulatory system; the respiratory system; the digestive system; and endocrine, nutritional, and metabolic diseases. Researchers have identified several factors showing seasonal variation that could possibly explain the seasonal variations in mortality rate. These factors include seasonal variations in solar ultraviolet-B(UVB) doses and serum 25-hydroxyvitamin D [25(OH)D] concentrations, gene expression, ambient temperature and humidity, UVB effects on environmental pathogen load, environmental pollutants and allergens, and photoperiod (or length of day). The factors with the strongest support in this analysis are seasonal variations in solar UVB doses and 25(OH)D concentrations. In the U.S., population mean 25(OH)D concentrations range from 21 ng/mL in March to 28 ng/mL in August. Measures to ensure that all people had 25(OH)D concentrations >36 ng/mL year round would probably reduce death rates significantly.

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