Effects of high ambient temperature on ambulance dispatches in different age groups in Fukuoka, Japan

ABSTRACT

Background: The elderly population has been the primary target of intervention to prevent heat-related illnesses. According to the literature, the highest risks have been observed among the elderly in the temperature–mortality relationship. However, findings regarding the temperature–morbidity relationship are inconsistent.

Objectives: This study aimed to examine the association of temperature with ambulance dispatches due to acute illnesses, stratified by age group. Specifically, we explored the optimum temperature, at which the relative health risks were found to be the lowest, and quantified the health risk associated with higher temperatures among different age groups.

Methods: We used the data for ambulance dispatches in Fukuoka, Japan, during May and September from 2005 to 2012. The data were grouped according to age in 20-year increments. We explored the pattern of the association of ambulance dispatches with temperature using a smoothing spline curve to identify the optimum temperature for each age group. Then, we applied a distributed lag nonlinear model to estimate the risks of the 85th–95th percentile temperature relative to the overall optimum temperature, for each age group.

Results: The relative risk of ambulance dispatches at the 85th and 95th percentile temperature for all ages was 1.08 [95% confidence interval (CI): 1.05, 1.12] and 1.12 (95% CI: 1.08, 1.16), respectively. In comparison, among age groups, the optimum temperature was observed as 25.0°C, 23.2°C, and 25.3°C for those aged 0–19, 60–79, and ≥80, respectively. The optimum temperature could not be determined for those aged 20–39 and 40–59. The relative risks of high temperature tended to be higher for those aged 20–39 and 40–59 than those for other age groups.

Conclusions: We did not find any definite difference in the effect of high temperature on ambulance dispatches for different age groups. However, more measures should be taken for younger and middle-aged people to avoid heat-related illnesses.

KEYWORDS:

• ambulance dispatch
• temperature
• distributed lag nonlinear model
• age category
• acute illness

Responsible Editor Peter Byass, Umeå University, Sweden

Responsible Editor Peter Byass, Umeå University, Sweden

Acknowledgments

This study was supported by the Global Environment Research Fund (S-12) of the Ministry of Environment in Japan.

Disclosure statement

No potential conflict of interest was reported by the authors.

Ethics and consent

Ethical approval for this study was provided by the Ethics Committee of the Graduate School of Engineering at Kyoto University.

Paper context

Several studies explored the temperature–mortality relationship and found that the elderly were susceptible to high temperature. However, there are relatively few studies characterizing the subgroups vulnerable to heat-related morbidity, and these results are inconsistent. The relative health risks of high temperature for younger and middle-aged people tended to be higher than that for the elderly people. More measures need to be taken for younger and middle-aged people to avoid heat-related illnesses.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This study was supported by the Environment Research and Technology Development Fund (S12) of the Environmental Restoration and Conservation Agency.

Notes on contributors

Hirohisa Takano

KK, KU, and HM collected the data. KK analyzed the data. KK wrote the manuscript, while KU, XS, SY, HM, MO, AH, and HT provided technical support during the drafting and editing phase.