The effects of ambient temperature on road traffic injuries in Jinan city: a time-stratified case-crossover study based on distributed lag nonlinear model

Abstract

Objectives: The impact of climate change, especially extreme temperatures, on health outcomes has become a global public health concern. Most previous studies focused on the impact of disease incidence or mortality, whereas much less has been done on road traffic injuries (RTIs). This study aimed to explore the effects of ambient temperature, particularly extreme temperature, on road traffic deaths in Jinan city.

Methods: Daily data on road traffic deaths and meteorological factors were collected among all residents in Jinan city during 2011-2020. We used a time-stratified case-crossover design with distributed lag nonlinear model to evaluate the association between daily mean temperature, especially extreme temperature and road traffic deaths, and its variation in different subgroups of transportation mode, adjusting for meteorological confounders.

Results: A total of 9,794 road traffic deaths were collected in our study. The results showed that extreme temperatures were associated with increased risks of deaths from road traffic injuries and four main subtypes of transportation mode, including walking, Bicycle, Motorcycle and Motor vehicle (except motorcycles), with obviously lag effects. Meanwhile, the negative effects of extreme high temperatures were significantly higher than those of extreme low temperatures. Under low-temperature exposure, the highest cumulative lag effect of 1.355 (95% CI, 1.054, 1.742) for pedal cyclists when cumulated over lag 0 to 6 day, and those for pedestrians, motorcycles and motor vehicle occupants all persisted until 14 days, with ORs of 1.227 (95% CI, 1.102, 1.367), 1.453 (95% CI, 1.214, 1.740) and 1.202 (95% CI, 1.005, 1.438), respectively. Under high-temperature exposure, the highest cumulative lag effect of 3.106 (95% CI, 1.646, 5.861) for motorcycle occupants when cumulated over lag 0 to 12 day, and those for pedestrian, pedal cyclists, and motor vehicle accidents all peaked when persisted until 14 days, with OR values of 1.638 (95% CI, 1.281, 2.094), 2.603 (95% CI, 1.695, 3.997) and 1.603 (95% CI, 1.066, 2.411), respectively.

Conclusion: This study provides evidence that ambient temperature is significantly associated with the risk of road traffic injuries accompanied by obvious lag effect, and the associations differ by the mode of transportation. Our findings help to promote a more comprehensive understanding of the relationship between temperature and road traffic injuries, which can be used to establish appropriate public health policies and targeted interventions.

Keywords: ambient temperature; case-crossover study; distributed lag nonlinear model; extreme temperature; road traffic injuries.

Figure 1

Exposure-response relationship between total RTIs deaths and daily mean temperature in Jinan city, 2011–2020. (A) Exposure-response curve. (B) 3D effect plot. (C) Contour plot.

Figure 2

The lagged-response curves for association between Daily Mean Temperature and RTIs fatalities in Jinan City, 2011–2020. (A) Single-day lagged low temperature. (B) Cumulative lagged low temperature. (C) Single-day lagged high-temperature. (D) Cumulative lagged high-temperature.

Figure 3

Cumulative Effects of extreme low-temperature and high-temperature on RTIs fatalities over lag days 0–14 in different subtypes of transport mode, in Jinan city, 2011–2020. (A) Cumulative effect at extreme low temperature (−6°C) on pedestrian injuries in transport accidents. (B) Cumulative effect at extreme low temperature (−6°C) on cyclist injuries in transport accidents. (C) Cumulative effect at extreme low temperature (−6°C) on motorcyclist injuries. (D) Cumulative effect at extreme low temperature (−6°C) on motor vehicle (except motorcycles) occupant injuries in transport accidents. (E) Cumulative effect at extreme high temperature (32°C) on pedestrian injuries in transport accidents. (F) Cumulative effect at extreme high temperature (32°C) in cyclist injuries in transport accidents. (G) Cumulative effect at extreme high temperature (32°C) on motorcyclist injuries in transport accidents. (H) Cumulative effect at extreme high temperature (32°C) on motor vehicle (except motorcycles) occupant injuries in transport accidents.