TOKYO REPORT: Extreme Heat Raises Risk of Preterm Births, Child Convulsions

Tokyo, May 25 (Jiji Press)–Extreme heat increases the risk of preterm births and can also lead to hospitalizations for childhood convulsions, according to new findings published by research teams at the Institute of Science Tokyo. Meanwhile, the Japan Meteorological Agency has released its latest three-month forecast, predicting higher-than-normal average temperatures nationwide from May through July. In light of the impending summer heat, officials stress that basic safety precautions, such as staying hydrated and utilizing air conditioning, are essential. Midpregnancy A research team led by Shuhei Terada, an assistant professor and specialist in perinatal medicine, analyzed data from about 986,000 births registered in the Japan Society of Obstetrics and Gynecology database between 2016 and 2020. To understand how climate affects pregnancy, the researchers examined the relationship between extreme heat and preterm delivery in each week of gestation. They focused on the months from May through September and defined “high-temperature weeks” as those in the top 10 pct of average weekly temperatures in each of Japan’s 47 prefectures. The findings indicate that women are particularly susceptible to the effects of heat between 16th and 22nd weeks. Most notably, expectant mothers who were exposed to severe heat during their 19th week of pregnancy faced a 16 pct higher risk of preterm birth than those who were not. Additionally, the study found that pregnant women under the age of 35 were more vulnerable to these heat-related effects than their older counterparts. Researchers attribute the heightened risk to the rapid fetal development and maternal bodily changes that occur in midpregnancy. According to the study, high temperatures can trigger inflammatory responses and other reactions that prematurely accelerate “cervical remodeling.” In this natural process, the cervix gradually softens and shortens in preparation for childbirth, rather than remaining firmly closed to protect the fetus. When heat induces the process too early, it can lead to preterm birth. “At the individual level, there is no need to immediately regard this as dangerous, but when considered at the population level, these figures cannot be ignored,” Terada said. He offered practical advice for those in their second trimester. “During the middle stage of pregnancy, expectant mothers should avoid spending long hours outdoors on extremely hot days, ensure they stay well-hydrated and use air conditioning appropriately.” Childhood Hospitalizations A separate Science Tokyo research team, led by professor Takeo Fujiwara and specially appointed assistant professor Aomi Katagiri, has identified a significant link between extreme temperatures and pediatric health emergencies. The team analyzed about 116,000 cases between 2011 and 2019 in which children aged 15 and under were admitted to emergency care for convulsions. The study revealed that extremely high daily average temperatures increased the risk of hospitalization by 17 pct, while extremely low temperatures drove the risk up by 22 pct. Notably, the risk of hospitalization peaked within one day of a major temperature shift. The team suggested that heat waves-related hospitalizations may be driven by dehydration and mineral deficiencies, such as sodium loss. During cold snaps, the increased risk is likely fueled by the rapid spread of infectious diseases. “Children may be vulnerable to extreme temperatures,” a member of the research team stated. “Measures against heat and cold, as well as preparedness in the medical system, are important.” Basic Precautions Between June and August last year, Japan recorded its highest average summer temperatures since its statistics began in 1898. Temperatures rose 2.36 degrees Celsius above the historical 30-year average through 2020. In response to this warming trend, the Japan Meteorological Agency announced in April this year that it will designate days with temperatures reaching 40 degrees or higher “kokushobi,” which translates as severely hot days. The agency warns that average temperatures are expected to exceed normal levels nationwide again this summer. To combat the heat, the health ministry is urging the public to take basic safety precautions. These include using air conditioning appropriately, staying hydrated, avoiding direct sunlight and regularly monitoring the heat index, also known as the Wet Bulb Globe Temperature, or WBGT. END [Copyright The Jiji Press, Ltd.]