Association between daily ambient temperature and drug overdose in Tokyo: a time-series study

Abstract

Background: Previous studies have reported that high ambient temperature is associated with increased risk of suicide; however, the association has not been extensively investigated with drug overdose which is the most common method of unsuccessful suicidal behavior in Japan. Therefore, this study aims to examine the short-term association between daily mean temperature and the incidence of self-harm attempts by drug overdose in Tokyo, Japan. Methods: We collected the emergency ambulance dispatch data and daily meteorological data in Tokyo from 2010 to 2014. A quasi-Poisson regression model incorporating a distributed lag non-linear function was applied to estimate the non-linear and delayed association between temperature and drug overdose, adjusting for relative humidity, seasonal and long-term trends, and days of the week. Sex, age and location-specific associations of ambient temperature with drug overdose was also estimated. Results: 12,937 drug overdose cases were recorded during the study period, 73.9% of which were female. We observed a non-linear association between temperature and drug overdose, with the highest risk observed at 21 °C. The highest relative risk (RR) was 1.30 (95% Confidence Interval (CI): 1.10-1.67) compared with the risk at the first percentile of daily mean temperature (2.9 °C) over 0-4 days lag period. In subgroup analyses, the RR of a drug overdose at 21 °C was 1.36 (95% CI: 1.02-1.81) for females and 1.07 (95% CI: 0.66-1.75) for males. Also, we observed that the risk was highest among those aged ²65 years (RR = 2.54; 95% CI: 0.94-6.90), followed by those aged 15-34 years (RR = 1.25; 95% CI: 0.89-1.77) and those aged 35-64 years (RR = 1.15; 95% CI: 0.78-1.68). There was no evidence for the difference in RRs between urban (23 special wards) and sub-urban areas in Tokyo. Conclusions: An increase in daily mean temperature was associated with increased drug overdose risk. This study indicated the positive non-linear association between temperature and incomplete attempts by drug overdose. The findings of this study may add further evidence of the association of temperature on suicidal behavior and suggests increasing more research and investigation of other modifying factors.

Short-term exposure to ambient temperature and the mortality burden of suicide in Japan

“…This is consistent with a broader body of existing studies investigating the association between ambient temperature and suicide in terms of relative risk in Japan [16,17,36]. Our findings are also consistent with a previous study in Tokyo, Japan, which indicated that an increase in daily mean temperature was nonlinearly associated with an increased risk of drug overdose, the most common method of unsuccessful suicide attempts in Japan [37]. Our findings also align with previous studies that showed higher relative risks for older people and women in Japan [16,17].…”

“…Our findings also align with previous studies that showed higher relative risks for older people and women in Japan [16,17]. Similarly, the previous study investigating the association between daily mean temperature and drug overdose using emergency ambulance dispatch data in Tokyo also found higher relative risks among older people and women [37]. However, the results from a multi-country study showed that the observed differences by sex and age group, with nonoverlapping confidence intervals, occur only in Japan and South Korea [16].…”

A protective role of urban greenspace on the association between night-time heat and suicide in Seoul, South Korea

“…In addition, opening windows on hot nights may increase noise-related stress, resulting in reduced quality of sleep (Murage et al 2017). Sleep deprivation or being awake at night due to hot nights can increase the use of alcohol or other substances, and social support declines during the night (Perlis et al 2016, Roy et al 2022. Furthermore, staying awake at night may decrease frontal lobe function, leading to diminished problem-solving abilities and increased impulsive behaviors (Perlis et al 2016).…”

“…As night-time heat can cause sleep disorders or sleep deprivation (Van Someren 2003), which potentially leads to an increase in the risk of suicide (Perlis et al 2016, Roy et al 2022, we hypothesized that districts, where people sleep less, have a higher risk of suicide for exposure to night-time heat. We tested this hypothesis by adding an interaction term between the hot night indices and the mean sleep hours (low vs. high) of each district in the model.…”

Effects of apparent temperature on daily outpatient and inpatient visits for cause-specific respiratory diseases in Ganzhou, China: a time series study

“…With increasing concerns about anthropogenic greenhouse gas emissions catalyzing the changes in global climate, health consequences arising from temperature have gained significant attention. Previous studies have found temperature adversely affected cardiovascular diseases [ 1 , 2 ], suicidal behavior [ 3 ], overall mortality [ 4 , 5 ] and other related outcomes [ 6 ]. Given that the respiratory system is directly and significantly influenced by temperature, its effects have been of greater concern than other systems.…”