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

J Steroid Biochem Mol Biol. 2017 Oct;173:5-12. doi: 10.1016/j.jsbmb.2017.01.003. Epub 2017 Jan 11.


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 21ng/mL in March to 28ng/mL in August. Measures to ensure that all people had 25(OH)D concentrations >36ng/mL year round would probably reduce death rates significantly.

Keywords: Cardiovascular disease; Gene expression; Mortality rate; Respiratory tract infections; Season; Temperature; Vitamin D.

Publication types

  • Review

MeSH terms

  • Cardiovascular Diseases / blood
  • Cardiovascular Diseases / genetics
  • Cardiovascular Diseases / mortality
  • Digestive System Diseases / blood
  • Digestive System Diseases / genetics
  • Digestive System Diseases / mortality
  • Environmental Pollutants / adverse effects
  • Gene Expression
  • Humans
  • Metabolic Diseases / blood
  • Metabolic Diseases / genetics
  • Metabolic Diseases / mortality
  • Mortality*
  • Nutrition Disorders / blood
  • Nutrition Disorders / genetics
  • Nutrition Disorders / mortality
  • Particulate Matter / adverse effects
  • Respiratory Tract Infections / blood
  • Respiratory Tract Infections / genetics
  • Respiratory Tract Infections / mortality
  • Seasons*
  • Sunlight
  • Ultraviolet Rays
  • United States / epidemiology
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood


  • Environmental Pollutants
  • Particulate Matter
  • Vitamin D
  • 25-hydroxyvitamin D