Exposure to temperatures of at least 35°C was associated with higher suicide risk scores in Bangladesh, with poor sleep quality emerging as a substantially stronger potential mediating pathway than emotional dysregulation, according to a nationally representative study published in Environmental Research. The observational analysis could not establish causation.
Investigators conducted a 2-round longitudinal panel study using nationally representative survey data collected from urban and rural households in Bangladesh during winter and summer 2024. The first survey, conducted from January 18 to February 7, included 7,492 participants aged 15 years or older, while the second, conducted from May 20 to June 7, included 7,490 participants. A balanced panel of 7,042 participants completed both rounds. The primary adjusted model included 14,861 observations across the 2 survey rounds. Investigators estimated heat exposure using meteorological data from 47 weather stations, examining the number of days with maximum temperatures of at least 25°C, 28°C, 30°C, 32°C, and 35°C during the 2 weeks preceding each survey.
The primary outcome was suicide risk, assessed using the Bangla version of the Brief Suicide Cognitions Scale, which measures perceived unlovability, unbearability, and unsolvability. Scores ranged from 6 to 30, with higher scores indicating greater risk. The investigators also assessed sleep quality using the Medical Outcomes Study Sleep Scale and emotional regulation using the Emotion Regulation Questionnaire. Adjusted analyses accounted for age, sex, disability status, household wealth, educational attainment, employment status, physical health conditions, time spent indoors, and urban or rural residence. Adjusted Tobit regression models assessed associations between heat exposure and suicide risk scores, while structural equation modeling examined potential statistical mediation through sleep quality and emotional dysregulation.
The association was strongest for days with maximum outdoor temperatures of at least 35°C. Each additional day reaching this threshold during the preceding 2 weeks was associated with an approximately 1-point higher suicide risk score in the adjusted model. The association was smaller at lower thresholds, with increases of 0.29 points at 32°C and 0.07 points at both 30°C and 28°C. Exposure at the 25°C threshold was not significantly associated with suicide risk in the adjusted analysis.
Mediation analysis showed that poor sleep quality accounted for 29.5% of the total modeled association between extreme heat exposure and suicide risk, corresponding to an indirect association of 0.08 points. Emotional dysregulation accounted for 1.8%, corresponding to an indirect association of 0.01 points. The remaining 69.5% was classified as the direct association in the statistical model, corresponding to 0.20 points. The mediation model estimated a total association of 0.29 points on the suicide risk scale.
Suicide risk scores were higher during summer than winter, increasing from a population-weighted mean of 11 to 13. Sleep quality scores also worsened, rising from 18.3 to 21.7, while emotional dysregulation scores increased from 16.1 to 18.6. Higher scores on all 3 measures indicated poorer outcomes.
Summer suicide risk scores also varied across demographic groups. Participants aged 65 years or older had the highest mean suicide risk scores during summer, at 13.5, compared with 12.5 among those aged 16 to 35 years. Women had slightly higher summer scores than men, at 13.1 vs 12.8, while urban residents had higher scores than rural residents, at 13.2 vs 12.9. However, age and sex were not independently associated with suicide risk in the primary adjusted model.
Socioeconomic characteristics showed more consistent associations. Compared with participants in the poorest wealth category, those in the middle and highest wealth categories had lower adjusted suicide risk scores by approximately 0.3 and 0.4 points, respectively. Higher educational attainment was also associated with lower risk scores, with reductions ranging from 0.6 points among participants who completed primary education to 1.5 points among those who completed tertiary education, compared with participants without formal education. Unemployment, disability, and urban residence were associated with higher adjusted scores.
Sensitivity analyses supported the primary findings, with the association between exposure to temperatures of at least 35°C and suicide risk remaining consistent across alternative regression models, a balanced panel of participants interviewed in both rounds, and models excluding sleep quality and emotional dysregulation. An additional analysis found no statistically significant association between suicide risk and heat exposure during the preceding 15 to 28 days, while the association with exposure during the preceding 1 to 2 weeks remained consistent.
Several limitations warrant consideration. Although the longitudinal design incorporated repeated observations, sleep quality, emotional regulation, and suicide risk were measured concurrently within each survey round, preventing confirmation of causal mediation. Suicide risk was assessed using a validated questionnaire rather than observed suicide attempts or deaths. Heat exposure was estimated from outdoor weather stations rather than individual measurements, potentially overlooking indoor conditions and nighttime temperatures. The analysis also lacked data on humidity, air pollution, rainfall, preexisting psychiatric disorders, substance use, stressful life events, previous suicide attempts, and access to mental health care, leaving potential residual confounding.
Investigators proposed that cooling infrastructure to improve sleeping conditions, alongside psychological interventions targeting emotional regulation, may warrant consideration in climate adaptation strategies. They identified dialectical behavior therapy (DBT), which has been used in Bangladesh to address suicidal outcomes, as one potential approach. “However, access to such services is restricted primarily due to cost and geographical concentration of providers in urban areas of the country,” wrote co-first study author Syed Shabab Wahid, DrPH, of Georgetown University in Washington, DC, and colleagues.
The investigators suggested that DBT could be adapted for community-based delivery by trained nonspecialist providers, with consideration of local cultural factors and mental health stigma. They also called for further research using more frequent or temporally separated measurements to determine whether the proposed pathways are causal.
The study received World Bank–administered funding. Wahid reported financial support from the World Bank. The remaining authors declared no competing interests.
Source: Environmental Research
