New US research has found evidence to support the long-held belief that those living in parts of the world where the days are shorter and colder drink more alcohol, potentially putting people at a higher risk of liver disease.
Carried out by researchers from the University of Pittsburgh Division of Gastroenterology, the new study set out to investigate if living in colder, darker climates causes people to consume more alcohol and what effect this may have on the risk of alcoholic cirrhosis.
The researchers gathered information on 193 sovereign countries as well as 50 states and 3,144 counties in the United States using data from the World Health Organization, the World Meteorological Organization and the Institute on Health Metrics and Evaluation.
They then looked at the associations between climate factors such as average temperature and sunlight hours, alcohol consumption (measured as total alcohol intake per capita), the percent of the population that drinks alcohol, and the rate of binge drinking.
The findings, published online in the journal Hepatology, showed that as the temperature and the number of daylight hours dropped, alcohol consumption increased.
The researchers also found evidence to suggest that colder, darker days also contribute to binge drinking and a higher rate of alcoholic liver disease, one of the main causes of death in those with prolonged excessive alcohol use. The same results were found both when comparing countries around the world and when comparing counties within the United States.
"It's something that everyone has assumed for decades, but no one has scientifically demonstrated it. Why do people in Russia drink so much? Why in Wisconsin? Everybody assumes that's because it's cold," said senior author Ramon Bataller, M.D., Ph.D. "But we couldn't find a single paper linking climate to alcoholic intake or alcoholic cirrhosis. This is the first study that systematically demonstrates that worldwide and in America, in colder areas and areas with less sun, you have more drinking and more alcoholic cirrhosis."
The team noted that they also took into account other factors which might influence how much a population drinks, for example, most of the Arab populations who live in hot, desert areas with a large number of sunlight hours would abstain from alcohol.
The researchers also controlled for health factors that might worsen the effects of alcohol on the liver, such as viral hepatitis, obesity and smoking.
"It's important to highlight the many confounding factors," said lead author Meritxell Ventura-Cots, Ph.D. "We tried to control for as many as we could. For instance, we tried to control for religion and how that influences alcohol habits."
They explained that those in colder climates may drink as alcohol is a vasodilator, meaning it increases the flow of warm blood to the skin, which is full of temperature sensors, and so can increase feelings of warmth. Drinking is also is linked to depression, which tends to be worse during winter months and when there is less sunlight.