Study: Heat death risk intervention tailoring should not stop at city level

Extreme heat is a leading cause of weather-related human mortality throughout much of the world, posing a significant burden when developing healthy and sustainable cities. But little research has been conducted on how impacts of risk factors for heat-related death can vary at city, city-region and neighbourhood levels.

An innovative study, recently published in the Elsevier journal Sustainable Cities and Society by researchers at Xi’an Jiaotong-Liverpool University, Harvard University and City University of Hong Kong, seeks to fill the research gap. The study analyses the impact of factors contributing to heat-related death at different spatial scales. (Spatial scale categorises the size of a space in which something occurs.) Factors the research considers include age, education, socioeconomic status, workplace, birthplace and environmental variables.

The study provides a framework for professionals such as geographers, urban planners, policymakers, environmental scientists and epidemiologists to better understand the spatial-scale dependent risk factors of heat-related mortality. In turn, greater understanding can inform strategies for heat-related death mitigation and further related research, says lead author Dr Jinglu Song of XJTLU.

Beyond top-down interventions

In urban planning, heat mitigation and climate change strategies too often use a top-down approach that does not effectively address specific conditions at the levels of the city, city-region and  neighbourhood levels, Dr Song says. The one-size-fits-all approach is less effective than a localised, spatial scale approach. 

To achieve this localised approach, the researchers presented a novel application of the Multiscale Geographically Weighted Regression (MGWR) to explore the scale of effect of each underlying risk factor. Hong Kong was used as the case study, but the MGWR techniques can be replicated in other regions, Dr Song says, but findings will vary depending on the area studied. (MGWR is used to study varying relationships in terms of geography.)

“Most cities in the Chinese mainland have a problem similar to Hong Kong—they have developed top-down interventions,” Dr Song says. “They don't consider much of a hierarchical strategy and rarely include site-specific action plans. According to our findings, some measures or interventions should not only be the responsibility of the provincial or municipal governments. They also need to consider community-oriented adaptive strategies. This can be a community centre, health agency and even volunteers taking the leading role instead of the city government.”

Measuring risk factors

Risks for heat-related death come from factors that might be only obvious at specific sites.

The researchers found that age and socioeconomic status were significant factors influencing risk over the whole city, with the elderly and the poor belonging to the population group most at risk, Dr Song explains. 

Some other risk factors exhibit more localised contributions to heat-related mortality, such as thermal environment and low income. Those findings suggest each region needs to be assessed individually to achieve answers that can address local conditions, Dr Song says.

The factor of birthplace was also observed as a contributor to heat-related mortality risk, she says. In particular, foreign immigrants in Hong Kong may come from different climates and find it hard to adjust to Hong Kong’s heat and humidity. This may weaken their adaptive capacities to extreme heat stress. In the face of an emergency or a disaster, they may also encounter language barriers and have trouble communicating and getting help, she says.

A hierarchical and site-specific climate action plan could broaden conventional adaptive strategies to include targeted interventions, such as additional healthcare institutions and medical personnel for the elderly.

“For effective heat mitigation and climate adaptive strategies, the responsibility of decision makers should be clarified at different administrative levels,” Dr Song says.

In addition to Dr Song, the study’s authors are Dr Hanchen Yu of Harvard University and Dr Yi Lu of City University of Hong Kong.