Periods of persistently high temperatures lead to an increase in gastrointestinal infections and can lead to flare-ups of chronic inflammatory bowel disease. We spoke to the Director of the Clinic for Gastroenterology and Hepatology Gerhard Rogler, Prof. Dr. med. Dr. phil., and the head physician Luc Biedermann, PD Dr. med.
You discovered the phenomenon back in 2013. Have there been any new findings on the connection between heat and gastrointestinal problems since then?
Luc Biedermann: The reasons why heat triggers gastrointestinal problems are still unclear. Various environmental influences are discussed as triggers: different lifestyles and diets or even heat. Of course, it is not just one factor that triggers gastrointestinal problems, it is about extremes, stress factors that are not good. These issues have attracted a great deal of interest in research in recent years.
Do you know more about the stress factors?
Gerhard Rogler: People adapt to their environment. We know, for example, that stays at high altitudes can also trigger relapses in chronically ill intestinal patients; this is particularly pronounced in patients who otherwise live at low altitudes. It’s the same with heat: people who live in temperate climates are more likely to suffer from heatwaves. Runners’ colitis, for example, is also known in marathon runners: in some cases they can develop intestinal inflammation. Another assumption is that the increased body temperature changes something in the intestinal flora.
LB: We are treating an unusually high number of patients with chronic bowel diseases on our ward this week. And many of those affected are currently writing to us that they are going through a relapse.
“Heat over several days is a stressful event for the body.”
Does that mean they have heat-induced relapses?
LB: We can only guess. It has been scientifically proven that physical and psychological stress can trigger relapses in chronic bowel patients. This also includes sleep deprivation, depression, long flights, etc. The exact cause of the relapses is not known to science. But one thing is clear: heat over several days is a stressful event for the body.
What advice would you give affected patients?
GR: In many cases, patients can avoid relapses if they avoid psychological or physical stress. It’s about recognizing triggers and preventing them. It is important for me to know that there is a connection between heat and the triggering of relapses so that I can give patients appropriate recommendations. It is also very important for chronic intestinal patients to avoid food-borne infections. They have to be even more careful than healthy people: A flare-up doesn’t just last two or three days, but puts those affected out of action for a longer period of time. However, infections and diarrheal diseases also increase in healthy people during heat waves, with a time lag of around five days.
Why do infections and diarrheal diseases increase during heat waves?
GR: These are often infectious diarrheal diseases. Bacteria such as Salmonella or Campylobacter typically grow at 37 degrees. The more the outside temperature adapts to this, the better they grow. They take a few days to become infectious because they have to multiply first. This is why it is important to make sure that the chicken is well grilled in summer.
LB: Dehydration could also play a role. If the body has too little water, this – combined with the necessary metabolic and circulatory adjustments – is a stress factor.
In the event of an infection: when do I need to see a doctor?
GR: The WHO recommends that you see a doctor if you have severe diarrhea. This is defined as no longer being able to be physically active, for example no longer being able to stand up. You should also see a doctor if you have a high temperature or have lost a lot of fluid. If you have diarrhea without restricting your physical activity for less than three to five days, a visit to the doctor is not absolutely necessary.
