The Effect of Meteorological, Pollution, and Geographic Exposures on Death by Suicide: A Scoping Review

The short-term effect of ambient particulate matter on suicide death

BACKGROUND

Air pollution can cause various respiratory and neurological diseases and continuous exposure can lead to death. Previous studies have reported that particulate matter (PM) exposure increases the risk of depression, suicidal thoughts, and suicidal death; however, the results are inconsistent and limited. This study aimed to examine the relationship between short-term PM exposure and suicide deaths, as well as investigate the short-term effects of PM on suicide death within vulnerable groups based on factors such as sex, age group, suicide-related information (note, method, and cause), psychiatric disorders, and physical diseases.

METHODS

Data on a total of 28,670 suicide deaths from 2013 to 2017, provided by the Korea Foundation for Suicide Prevention, were analyzed. The study design employed a time-series analysis with a two-stage approach. In the first step, a generalized additive model combined with a distributed lag nonlinear model was used to estimate the short-term effect of PM exposure on suicide risk specific to each city. In the second step, the estimated results from each city were pooled through a meta-analysis to derive the overall effect. We determined the effects of single lag, cumulative lag, and moving average PM concentrations from days 0-7 before suicide.

RESULTS

We confirmed an association between exposure to PM10 (≤ 10 μm in diameter) and deaths due to suicide. In particular, among individuals with psychiatric disorders and those who employed non-violent suicide methods, increased exposure to PM10 was associated with a higher risk of death by suicide, with percentage changes of 5.92 (95% confidence interval [CI]: 3.95-7.92) and 11.47 (95% CI: 7.95-15.11), respectively. Furthermore, in the group with psychiatric disorders, there was an observed tendency of increasing suicide risk as PM10 levels increased up to 120 µg/m3, whereas in the group with non-violent suicide deaths, there was a pronounced trend of rapid increase in suicide risk with an increase in PM10 up to 100 µg/m3.

CONCLUSIONS

These results show an association between short-term exposure to PM and suicide. Our study adds evidence for the benefits of reducing PM in preventing diseases and improving mental health.

Ambient temperature and mental health: a systematic review and meta-analysis

BACKGROUND

Increasing evidence indicates that ambient outdoor temperature could affect mental health, which is especially concerning in the context of climate change. We aimed to comprehensively analyse the current evidence regarding the associations between ambient temperature and mental health outcomes.

METHODS

We did a systematic review and meta-analysis of the evidence regarding associations between ambient outdoor temperature and changes in mental health outcomes. We searched WebOfScience, Embase, PsychINFO, and PubMed for articles published from database origin up to April 7, 2022. Eligible articles were epidemiological, observational studies in humans of all ages, which evaluated real-world responses to ambient outdoor temperature, and had mental health as a documented outcome; studies of manipulated or controlled temperature or those with only physical health outcomes were excluded. All eligible studies were synthesised qualitatively. If three or more studies reported the same or equivalent effect statistics and if they had equivalent exposure, outcome, and metrics, the studies were pooled in a random-effects meta-analysis. The risk of bias for individual studies was assessed using the Newcastle-Ottawa Scale. The quality of evidence across studies was assessed using the Office of Health Assessment and Translation (OHAT) approach.

FINDINGS

114 studies were included in the systematic review, of which 19 were suitable for meta-analysis. Three meta-analyses were conducted for suicide outcomes: a 1°C increase in mean monthly temperature was associated with an increase in incidence of 1·5% (95% CI 0·8-2·2, p<0·001; n=1 563 109, seven effects pooled from three studies); a 1°C increase in mean daily temperature was associated with an increase in incidence of 1·7% (0·3-3·0, p=0·014; n=113 523, five effects pooled from five studies); and a 1°C increase in mean monthly temperature was associated with a risk ratio of 1·01 (95% CI 1·00-1·01, p<0·001; n=111 794, six effects pooled from three studies). Three meta-analyses were conducted for hospital attendance or admission for mental illness: heatwaves versus non-heatwave periods were associated with an increase in incidence of 9·7% (95% CI 7·6-11·9, p<0·001; n=362 086, three studies); the risk ratio at the 99th percentile of daily mean temperature compared with the 50th percentile was 1·02 (95% CI 1·01-1·03, p=0·006; n=532 296, three studies); and no significant association was found between a 10°C increase in daily mean temperature and hospital attendance. In a qualitative narrative synthesis, we found that ambient outdoor temperature (including absolute temperatures, temperature variability, and heatwaves) was positively associated with attempted and completed suicides (86 studies), hospital attendance or admission for mental illness (43 studies), and worse outcomes for community mental health and wellbeing (19 studies), but much of the evidence was of low certainty with high heterogeneity.

INTERPRETATION

Increased temperature and temperature variability could be associated with increased cases of suicide and suicidal behaviour, hospital attendance or admission for mental illness, and poor community health and wellbeing. Climate change is likely to increase temperature anomalies, variability, and heatwaves as well as average temperatures; as such, health system leaders and policy makers must be adequately prepared and should develop adaptation strategies. More high-quality, standardised research is required to improve our understanding of these effects.

FUNDING

None.

Relationship of emergency department visits for suicide attempts with meteorological and air pollution conditions

BACKGROUND

Environmental factors such as meteorological and air pollution conditions have been identified as risk factors for suicide. This study aimed to clarify the relationship of the number of visits to the emergency department for suicide attempts with meteorological and air pollution conditions.

METHODS

This cross-sectional study included patients who attempted suicide and were transported to Yokohama City University Medical Center from April 2005 to March 2022. The meteorological conditions recorded at the time of transport included mean atmospheric pressure, mean temperature, maximum temperature, minimum temperature, mean humidity, wind speed, and sunshine hours, and the air pollution conditions included SO₂ (ppm), NO (ppm), NO₂ (ppm), NOX (ppm), OX (ppm), CH₄ (ppmC), NMHC (ppmC), THC (ppmC), SPM (μg/m³), and PM2.5 (μg/m³). Poisson regression analysis was used to examine the association between the number of suicide attempts and the meteorological and air pollution conditions. Subgroup analyses were conducted by classifying the subjects according to the means of suicide attempt; comparisons were performed using t-tests.

RESULTS

The study included 1737 patients. Multivariate Poisson regression analyses revealed a significant positive relationship between the number of suicide attempts and SO₂ levels and a significant negative relationship between the number of suicide attempts and NO levels. When subjects were divided by means of suicide attempt, different relationships with meteorological and air pollution conditions were observed.

CONCLUSION

Meteorological and air pollution conditions are environmental factors that can enable a more detailed understanding of suicide behavior according to the means of suicide attempts.

Scrutinizing the Profile and Risk Factors of Suicide: A Perspective from a Case-Control Study Focused on a Northern Region of Spain

Suicide is a major public health problem the prevention of which has become a priority, and, to this end, knowledge of its risk factors is essential. This study aims to evaluate the impact of some social, medico-legal, and clinical issues on suicide deaths. A total of 135 cases were identified as suicides that occurred in a region of northern Spain between 2018 and 2020. Controls (three for each case) were matched by age, sex, and urban-rural areas. The information was collected retrospectively through electronic health record systems. A binary logistic regression analysis was performed to study the association between individual risk factors and suicide. Being male (78.5%), between 40 and 60 years of age, unmarried (70.9%), and unemployed (85%) were associated with suicide deaths. Although the existence of a previous self-harm attempt is presented as the most robust risk factor (OR 22.121 [8.997-54.389]), the presence of a psychiatric diagnosis (OR 12.583 [7.686-20.601]) and cancer (OR 3.729 [1.845-7.536]) also showed a significant relationship with suicide (p < 0.05). Defining and knowing the risk factors for suicide helps to better understand the profiles of those individuals who are vulnerable, and enables prevention actions to be taken in both social and medical spheres.

Spatial and space-time clusters of suicides in the contiguous USA (2000-2019)

The present study investigates the spatiotemporal variations in suicide mortality and tests associations between several covariates and suicides for the years 2000-2019 in the contiguous USA. The epidemiological disease surveillance software (SaTScan^TM) was used to identify spatiotemporal variations in suicide mortality rates and to test for significant spatial and space-time clusters with elevated relative suicide risk. The analysis was done with age-adjusted suicide mortality counts data from the Centers for Disease Control (CDC) with (International Classification of Diseases) ICD-10 codes. Specifically, data with codes ICD-10 codes X60-X84.9 and Y87.0, plus ICD-10 113 codes from the CDC, was used. Fourteen significant spatial clusters and five significant space-time clusters of suicide in the contiguous USA were found, including nine significant bivariate spatial clusters of suicide deaths and opioid deaths. Based on these data, there exist significant and non-random suicide mortality clusters after adjusting for multiple covariates or risk factors. The covariates studied provide evidence to develop a better understanding of possible associations in geographical areas where the suicide mortality rates are higher than expected. In addition, there is a significant association between several of the studied risk factors and suicide mortality. While most suicide clusters are also opioid clusters, there exist some clusters with high opioid deaths that are not suicide clusters. These results have the potential to provide a scientific framework that is based on surveillance, allowing health agencies to intervene and reduce elevated rates of suicides in selected counties in the U.S. The study is limited due to the resolution of the data at the county level, and some covariate data was unavailable for the entire period of the study.

Short-term changes in meteorological conditions and suicide: A systematic review and meta-analysis

BACKGROUND

Suicide is a leading cause of death, particularly for young adults. Suicidal behaviours are influenced by a wide-range of personal, social, and cultural factors. Emerging evidence suggests that daily changes in meteorological conditions, including temperature, increases the risk of suicide.

METHODS

We conducted a systematic review and meta-analysis of studies that examined associations between either daily, or weekly, variations for eight meteorological variables and suicide outcomes (attempts, or deaths). Meta-analytic methods were applied to derive summary measures of association using random effect models. We assessed the heterogeneity in these associations by region and biological sex.

RESULTS

We identified 29 studies of suicide. Of these, 26 reported associations between temperature, while fewer studies reported on rain (n = 4), solar radiation (n = 4), humidity (n = 3), sunshine (n = 3), atmospheric pressure (n = 2), wind (n = 2) and cloud cover (n = 2). The overall relative risk for suicide deaths/attempts per 1 °C increase in ambient temperature was 1.016 (95% CI: 1.013-1.019). Subgroup analysis of temperature found stronger associations with suicide when using the maximum rather than the mean daily temperature, among men, and for completed suicides relative to attempts. Regionally, the strongest associations were found in the East Asia and Pacific region. While associations were found for solar radiation and cloud coverage and suicide, we did not undertake a meta-analysis for these exposures as it was not possible to standardize measures of association across studies. Statistically significant associations were not observed for other identified meteorological variables.

CONCLUSIONS

Our findings suggest that daily increases in temperature increase the risk of suicide, particularly, among men and in the East Asia and Pacific region.