Daily heat stress sending children to hospital

A plethora of life-long issues may begin affecting New Zealand children as the days heat up. While sunburn and dehydration might be the immediate health concerns during hot summer days, a new Waipapa Taumata Rau, University of Auckland study shows that when the mercury reaches beyond 24.1 degrees Celsius, childhood hospital admissions rise for all sorts of ailments.

Epidemiologists from the Faculty of Medical and Health Sciences explored the relationship between childhood health and changes in daily temperatures. The researchers crunched 20 years of data on daily maximum temperature between 2000 and 2019 alongside information about the principal and secondary causes of 647,000 hospital admissions for children under the age of five.

Dr Hakkan Lai, a senior research fellow in epidemiology and biostatistics, says infectious diseases, blood and immune disorders, and diseases related to the kidney, skin and tissues, and nervous system were among the number of diagnoses associated with the effect of heat on young children.

“We can see hospital admissions increase from the first day of high temperature,” he says. “After that, pronounced delayed effects are still evident three weeks later.”

The link between heat stress and child hospitalisations is consistent with previous studies in the US and Australia and, Lai says, the surging risks in various diseases can be “explained due to dehydration, cardiovascular strain and inflammatory damage. These responses can overwhelm the body, potentially leading to worsening of pre-existing conditions”.

He says young children are more significantly affected by heat compared with adults for several reasons including their faster metabolism, and their smaller bodies heating up more quickly.

The research, funded by the Health Research Council in 2022, also uncovered that the relative risk of heat stress is not uniform for all children around New Zealand.

“Preschoolers’ vulnerability to heat stress appears to be highly sensitive to daily temperature changes and is unevenly distributed across the population.

“Unsurprisingly, geography plays a part. Our research shows young children living in Central Otago, Central Canterbury and the East Coast, as well as those in densely populated areas, have greater sensitivity to daily temperature changes than those in other areas. Interestingly though, when we look very closely, there are some notable differences suburb by suburb.

“There are ethnic, sex and socio-economic differences. At temperatures above the reference temperature of 24.1°C, Pacific, Asian and Māori pre-schoolers present to hospital more frequently than European children.”

For example, in every 1°C increase from 30°C to 35°C, Pacific children accounted for a 34 percent increased risk of hospital admissions associated with daily heat changes, Asian children 28 percent, Māori children 20 percent, and sole European 12 percent. Conversely, children new to New Zealand were less sensitive to heat but much more sensitive to cold compared to those who were New Zealand born.

Boys seemed less sensitive to daily temperature than girls. Children who lived in homes owned by their caregivers appeared to be less susceptible to heat, compared with those living in rental properties.

Over the last seven years of this 20-year period, an estimated 290 preschooler hospital admissions were attributable to heat effects every year. Using 24.1°C as the reference temperature, data modelling from the study projects that number to rise rapidly with each 1°C increase, reaching up to 1,300 admissions with a 3°C increase.

Lai says this research is important in signalling risk and allows for timely well-directed policy and practical interventions to be put in place.

“As we anticipate rising temperatures as our climate changes, heat stress on children is particularly pressing.

“There are implications for the health sector such as planning, funding and distribution of paediatric services, also longer-term planning for central and local government in health, housing, urban design to moderate the effect of higher summer temperatures.”

Lai is seeking funding to extend this research to delve more closely into the New Zealand data to discover more clues that will help prepare for the impact of climate change on the nation’s health.

The research was published in the International Journal of Environmental Research and Publich Health. See the full paper.