Ambient Heat and Sudden Infant Death
Ambient Heat and Sudden Infant Death
Background: Climate change may lead to more severe and extreme heat waves in the future, but its potential impact on sudden infant death—a leading cause of infant mortality—is unclear.
Objectives: We sought to determine whether risk of sudden infant death syndrome (SIDS) is elevated during hot weather.
Methods: We undertook a case-crossover analysis of all sudden infant deaths during warm periods in metropolitan Montreal, Quebec, Canada, from 1981 through 2010. Our analysis included a total of 196 certified cases of SIDS, including 89 deaths at 1–2 months of age, and 94 at 3–12 months. We estimated associations between maximum outdoor temperatures and SIDS by comparing outdoor temperatures on the day of or day before a SIDS event with temperatures on control days during the same month, using cubic splines to model temperature and adjusting for relative humidity.
Results: Maximum daily temperatures of ≥ 29°C on the same day were associated with 2.78 times greater odds of sudden infant death relative to 20°C (95% CI: 1.64, 4.70). The likelihood of sudden death increased steadily with higher temperature. Associations were stronger for infants 3–12 months of age than for infants 1–2 months of age, with odds ratios of 3.90 (95% CI: 1.87, 8.13) and 1.73 (95% CI: 0.80, 3.73), respectively, for 29°C compared with 20°C on the day of the event.
Conclusions: High ambient temperature may be a novel risk factor for SIDS, especially at ≥ 3 months of age. Climate change and the higher temperatures that result may account for a potentially greater proportion of sudden infant deaths in the future.
Sudden infant death syndrome (SIDS) is a leading cause of death among infants 1–12 months of age, but its underlying risk factors are poorly understood (Kinney and Thach 2009; Moon et al. 2007). Despite rates that decreased following international campaigns to promote supine sleep positions in the 1990s, SIDS continues to be an important cause of postneonatal mortality in countries throughout Europe and the United States (Hauck and Tanabe 2008; Kinney and Thach 2009; Moon et al. 2007).
Evidence suggests that the underdeveloped thermoregulatory capacity of infants increases susceptibility to thermal stress and risk of sudden death (Guntheroth and Spiers 2001). Although numerous studies have shown that SIDS is associated with exposures such as overwrapping, bundling, and other behaviors linked with overheating (Guntheroth and Spiers 2001; Task Force on Sudden Infant Death Syndrome and Moon 2011), surprisingly little research documents whether outdoor heat is a risk factor. This is particularly concerning in light of climate change, which is expected to lead to more frequent and intense heat waves in the future (Intergovernmental Panel on Climate Change 2013). Several studies have reported that extreme heat is associated with higher mortality in the elderly (Baccini et al. 2008; Basagaña et al. 2011; Smargiassi et al. 2009), but the only studies that to our knowledge investigated a possible association with SIDS used ecologic methods and reported no associations with elevated temperature (Chang et al. 2013; Scheers-Masters et al. 2004). The paucity of research on high temperature using individual-level data on SIDS is concerning, considering that extreme ambient heat is a biologically plausible risk factor, and that more intense heat waves this century are imminent.
In response to the call for research on future impacts of climate change and extreme heat waves on the health of infants (Shea and American Academy of Pediatrics Committee on Environmental Health 2007), we sought to measure the association between high outdoor ambient temperature and SIDS in a large North American metropolitan center.
Abstract and Introduction
Abstract
Background: Climate change may lead to more severe and extreme heat waves in the future, but its potential impact on sudden infant death—a leading cause of infant mortality—is unclear.
Objectives: We sought to determine whether risk of sudden infant death syndrome (SIDS) is elevated during hot weather.
Methods: We undertook a case-crossover analysis of all sudden infant deaths during warm periods in metropolitan Montreal, Quebec, Canada, from 1981 through 2010. Our analysis included a total of 196 certified cases of SIDS, including 89 deaths at 1–2 months of age, and 94 at 3–12 months. We estimated associations between maximum outdoor temperatures and SIDS by comparing outdoor temperatures on the day of or day before a SIDS event with temperatures on control days during the same month, using cubic splines to model temperature and adjusting for relative humidity.
Results: Maximum daily temperatures of ≥ 29°C on the same day were associated with 2.78 times greater odds of sudden infant death relative to 20°C (95% CI: 1.64, 4.70). The likelihood of sudden death increased steadily with higher temperature. Associations were stronger for infants 3–12 months of age than for infants 1–2 months of age, with odds ratios of 3.90 (95% CI: 1.87, 8.13) and 1.73 (95% CI: 0.80, 3.73), respectively, for 29°C compared with 20°C on the day of the event.
Conclusions: High ambient temperature may be a novel risk factor for SIDS, especially at ≥ 3 months of age. Climate change and the higher temperatures that result may account for a potentially greater proportion of sudden infant deaths in the future.
Introduction
Sudden infant death syndrome (SIDS) is a leading cause of death among infants 1–12 months of age, but its underlying risk factors are poorly understood (Kinney and Thach 2009; Moon et al. 2007). Despite rates that decreased following international campaigns to promote supine sleep positions in the 1990s, SIDS continues to be an important cause of postneonatal mortality in countries throughout Europe and the United States (Hauck and Tanabe 2008; Kinney and Thach 2009; Moon et al. 2007).
Evidence suggests that the underdeveloped thermoregulatory capacity of infants increases susceptibility to thermal stress and risk of sudden death (Guntheroth and Spiers 2001). Although numerous studies have shown that SIDS is associated with exposures such as overwrapping, bundling, and other behaviors linked with overheating (Guntheroth and Spiers 2001; Task Force on Sudden Infant Death Syndrome and Moon 2011), surprisingly little research documents whether outdoor heat is a risk factor. This is particularly concerning in light of climate change, which is expected to lead to more frequent and intense heat waves in the future (Intergovernmental Panel on Climate Change 2013). Several studies have reported that extreme heat is associated with higher mortality in the elderly (Baccini et al. 2008; Basagaña et al. 2011; Smargiassi et al. 2009), but the only studies that to our knowledge investigated a possible association with SIDS used ecologic methods and reported no associations with elevated temperature (Chang et al. 2013; Scheers-Masters et al. 2004). The paucity of research on high temperature using individual-level data on SIDS is concerning, considering that extreme ambient heat is a biologically plausible risk factor, and that more intense heat waves this century are imminent.
In response to the call for research on future impacts of climate change and extreme heat waves on the health of infants (Shea and American Academy of Pediatrics Committee on Environmental Health 2007), we sought to measure the association between high outdoor ambient temperature and SIDS in a large North American metropolitan center.
