Japan's recent record-breaking heat poses health risks other than heatstroke, a study by the Institute of Science Tokyo shows.

The team found that the risk of serious complications for pregnant women increases the day after a heat wave. Previous studies also reported worsening symptoms of diabetes and respiratory illnesses, making precautions against these related health risks even more important.

Takeo Fujiwara, a professor at the university, and his team analyzed the link between the wet bulb globe temperature (WBGT) heat stress index and about 6,900 cases reported from 11 regions in Japan in 2011-2020 of placental abruption, in which part of the placenta separates from the uterus before childbirth.

The risk of developing placental abruption was 1.2 times higher the day after a particularly high WBGT day. The risk increased 1.5 times among those with hypertensive disorders of pregnancy and 1.4 times among those with fetal growth restriction.

A previous study of people with diabetes found that the risk of hospitalization for hyperglycemia and hypoglycemia rose by over 1.6 times on days with an average temperature of 29 degrees Celsius compared to days with an average of 22 C.

Dehydration is said to be the cause of the increased risks, with attention required especially for patients using insulin.

Health risks stemming from torrid temperatures also extend to children.

According to another study, exposure to extreme heat led to a 1.2 times increase in the risk of hospitalization for asthma, with the risk rising 1.3 times for those the age of 14 or younger.

Based on climate change and demographics, the risk of being hospitalized for heat-related asthma could increase by up to 4.1 times in the 2090s, according to the study.

As basic measures to cope with the heat, Japan's health ministry is calling on people to use air conditioners, monitor WBGT levels, stay hydrated and avoid direct sunlight.