Winter immune boost may actually cause deaths, study suggests
The increase in deaths during winter months is typically put down to icy weather, bouts of flu and the more sluggish lifestyles we adopt as the days draw in. Now scientists have suggested that our own immune systems may be to blame for the annual peak in conditions from heart attacks to diabetes and schizophrenia.
A study has revealed that the immune system has a seasonal cycle, in which its activity is boosted during the winter and relaxes during the summer.
The winter increase in immune defences ought to help stave off infections, such as flu, but also raises the risk of harmful inflammation in the body, effectively lowering the threshold for heart attacks, stroke, diabetes and even some psychiatric conditions.
The latest work suggests that our own immune systems could be “tipping us over the edge” into illness - or even death. In the future, doctors may be able to reduce this peak, by prescribing medicines, such as statins, diabetic drugs and anti-depressants on a seasonal basis, the scientists suggested.
In the latest work, scientists analysed blood samples from more than 16,000 people living in both the northern and southern hemispheres, in countries including
One gene, known as ARNTL, that was seen to be more active in the summer, has previously been shown in mice to suppress inflammation, the body’s response to infection. Many other immune genes followed a similar trend, the study found.
In the past, our seasonal immune cycle may have given us a powerful evolutionary advantage in the winter months, when the main cause of fatalities would have been disease and hunger. “You have to take yourself back to prehistoric humans who suffered cold and starvation in the winter,” said Todd. “It would’ve been a really perilous situation.”
In these conditions, even a slight boost to the readiness of the immune system could improve survival chances.
However, the inflammatory molecules that flood the body during an immune response have a downside – they can attack the body’s own tissues causing conditions from diabetes to heart attack and stroke. More recent studies have shown compelling links between inflammatory markers and mental health, from schizophrenia, severe depression and Alzheimer’s disease.
In the modern world, the disadvantages of the winter peak in immune activity may have come to outweigh the benefits, the researchers suggest.
Drugs that target the mechanisms behind inflammation could offer a way of helping treat these diseases more effectively during the winter periods.
The study also found people from the
“We know that humans adapt to changing environments,” said Dr
The findings are published in the journal