Acute Air Pollution Exposure and Risk of Suicide Completion
Acute Air Pollution Exposure and Risk of Suicide Completion
Research into environmental factors associated with suicide has historically focused on meteorological variables. Recently, a heightened risk of suicide related to short-term exposure to airborne particulate matter was reported. Here, we examined the associations between short-term exposure to nitrogen dioxide, particulate matter, and sulfur dioxide and completed suicide in Salt Lake County, Utah (n = 1,546) from 2000 to 2010. We used a time-stratified case-crossover design to estimate adjusted odds ratios for the relationship between suicide and exposure to air pollutants on the day of the suicide and during the days preceding the suicide. We observed maximum heightened odds of suicide associated with interquartile-range increases in nitrogen dioxide during cumulative lag 3 (average of the 3 days preceding suicide; odds ratio (OR) = 1.20, 95% confidence interval (CI): 1.04, 1.39) and fine particulate matter (diameter ≤2.5 μm) on lag day 2 (day 2 before suicide; OR = 1.05, 95% CI: 1.01, 1.10). Following stratification by season, an increased suicide risk was associated with exposure to nitrogen dioxide during the spring/fall transition period (OR = 1.35, 95% CI: 1.09, 1.66) and fine particulate matter in the spring (OR = 1.28, 95% CI: 1.01, 1.61) during cumulative lag 3. Findings of positive associations between air pollution and suicide appear to be consistent across study locations with vastly different meteorological, geographical, and cultural characteristics.
Suicide is the tenth leading cause of death in the United States and the eighth leading cause in Utah. Multiple interacting factors influence a person's risk of suicide, including the presence of psychiatric and/or physical illness, previous and current social experiences, genetic susceptibility, and exposure to environmental factors. Despite being recognized as major contributors to suicide risk, the environmental risk factors associated with suicide remain poorly understood.
Research into the environmental factors associated with suicide has focused largely on the relationship between suicide risk and meteorological variables. Peak suicide rates have been shown to be positively correlated with increasing durations of sunshine and ambient temperatures and negatively correlated with decreasing amounts of precipitation. Recently, the search for environmental risk factors associated with suicide has broadened beyond meteorological variables to include exposure to air pollutants. Studies conducted in the Republic of Korea and Taiwan have identified a heightened risk of suicide related to short-term exposure to particulate matter. Further, Kim et al. conducted a stratified analysis and found that suicide risk was greatest among males and persons aged 36–64 years, while a peak seasonal association was identified during the "transition period," defined as spring and fall combined.
A similar relationship may exist between air pollution and suicide risk in US populations, but this has yet to be examined. Substantial differences in epidemiologic suicide patterns, including higher average suicide rates, lower male:female suicide ratios, and higher elderly:general population suicide ratios in Asian countries compared with the United States, suggest that the relationship between air pollution exposure and suicide in US populations may be hard to predict based on recent findings in Asian populations.
In this study, we used a time-stratified case-crossover design to investigate the associations between acute exposure to airborne particulate matter and gaseous air pollutants (nitrogen dioxide and sulfur dioxide) and suicide risk among completed suicides occurring in Salt Lake County, Utah, from 2000 to 2010. The Salt Lake Valley regularly experiences wintertime inversions (a product of its geography and weather), in which a mass of trapped cold air blankets the valley floor. These intermittent inversions are often characterized by an accumulation of air pollutants with daily average levels exceeding the Environmental Protection Agency's National Ambient Air Quality Standards. Researchers have used data from these winter inversion events, in contrast with data from improved wintertime air quality days, to describe associations between air pollution and increased rates of daily mortality, hospital admissions for respiratory disease, and emergency department visits for asthma. We hypothesized that Salt Lake County's poor wintertime air quality might show similar adverse associations with risk of suicide completion.
Our primary objectives in this study were to investigate the suicide risk associated with short-term air pollution exposure. In addition, we examined how the relationship between acute air pollution and suicide risk varied by suicide characteristics, including season, method of death (violent vs. nonviolent), sex, and age.
Abstract and Introduction
Abstract
Research into environmental factors associated with suicide has historically focused on meteorological variables. Recently, a heightened risk of suicide related to short-term exposure to airborne particulate matter was reported. Here, we examined the associations between short-term exposure to nitrogen dioxide, particulate matter, and sulfur dioxide and completed suicide in Salt Lake County, Utah (n = 1,546) from 2000 to 2010. We used a time-stratified case-crossover design to estimate adjusted odds ratios for the relationship between suicide and exposure to air pollutants on the day of the suicide and during the days preceding the suicide. We observed maximum heightened odds of suicide associated with interquartile-range increases in nitrogen dioxide during cumulative lag 3 (average of the 3 days preceding suicide; odds ratio (OR) = 1.20, 95% confidence interval (CI): 1.04, 1.39) and fine particulate matter (diameter ≤2.5 μm) on lag day 2 (day 2 before suicide; OR = 1.05, 95% CI: 1.01, 1.10). Following stratification by season, an increased suicide risk was associated with exposure to nitrogen dioxide during the spring/fall transition period (OR = 1.35, 95% CI: 1.09, 1.66) and fine particulate matter in the spring (OR = 1.28, 95% CI: 1.01, 1.61) during cumulative lag 3. Findings of positive associations between air pollution and suicide appear to be consistent across study locations with vastly different meteorological, geographical, and cultural characteristics.
Introduction
Suicide is the tenth leading cause of death in the United States and the eighth leading cause in Utah. Multiple interacting factors influence a person's risk of suicide, including the presence of psychiatric and/or physical illness, previous and current social experiences, genetic susceptibility, and exposure to environmental factors. Despite being recognized as major contributors to suicide risk, the environmental risk factors associated with suicide remain poorly understood.
Research into the environmental factors associated with suicide has focused largely on the relationship between suicide risk and meteorological variables. Peak suicide rates have been shown to be positively correlated with increasing durations of sunshine and ambient temperatures and negatively correlated with decreasing amounts of precipitation. Recently, the search for environmental risk factors associated with suicide has broadened beyond meteorological variables to include exposure to air pollutants. Studies conducted in the Republic of Korea and Taiwan have identified a heightened risk of suicide related to short-term exposure to particulate matter. Further, Kim et al. conducted a stratified analysis and found that suicide risk was greatest among males and persons aged 36–64 years, while a peak seasonal association was identified during the "transition period," defined as spring and fall combined.
A similar relationship may exist between air pollution and suicide risk in US populations, but this has yet to be examined. Substantial differences in epidemiologic suicide patterns, including higher average suicide rates, lower male:female suicide ratios, and higher elderly:general population suicide ratios in Asian countries compared with the United States, suggest that the relationship between air pollution exposure and suicide in US populations may be hard to predict based on recent findings in Asian populations.
In this study, we used a time-stratified case-crossover design to investigate the associations between acute exposure to airborne particulate matter and gaseous air pollutants (nitrogen dioxide and sulfur dioxide) and suicide risk among completed suicides occurring in Salt Lake County, Utah, from 2000 to 2010. The Salt Lake Valley regularly experiences wintertime inversions (a product of its geography and weather), in which a mass of trapped cold air blankets the valley floor. These intermittent inversions are often characterized by an accumulation of air pollutants with daily average levels exceeding the Environmental Protection Agency's National Ambient Air Quality Standards. Researchers have used data from these winter inversion events, in contrast with data from improved wintertime air quality days, to describe associations between air pollution and increased rates of daily mortality, hospital admissions for respiratory disease, and emergency department visits for asthma. We hypothesized that Salt Lake County's poor wintertime air quality might show similar adverse associations with risk of suicide completion.
Our primary objectives in this study were to investigate the suicide risk associated with short-term air pollution exposure. In addition, we examined how the relationship between acute air pollution and suicide risk varied by suicide characteristics, including season, method of death (violent vs. nonviolent), sex, and age.
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