Table 2.
Summary of study findings that assess temperature effects on all-cause infant mortality and SIDS.
| Main Author (Year) | Research Design | Location, Year of Study | Description of Climate | Main Temperature Exposure Variable(s) | Statistical Analysis | Outcomes Measure (Source of Data) | Effect Estimates |
|---|---|---|---|---|---|---|---|
| All-Cause Mortality | |||||||
| Basu (2008) [35] | Case-crossover | California, USA 1999–2003 | Mean apparent temperature in warm season: 21.4 °C | Mean daily apparent temperature. Lag 0 days | Time-stratified case-crossover | Nonaccidental infant death. Sample size not provided for this age group (routine data) | 4.9% (95%CI = 1.0, 7.1%) increase in mortality for every 4.7 °C increase in temperature (no threshold presented). |
| Basu (2015) [21] | Case-crossover | California, USA, 1999–2011 | Mean temperature in warm season in coastal area, 17.8 °C and in non-coastal area 20.8 °C | Mean daily apparent temperature in warm season. Lag 0–3 days | Time-stratified case-crossover | 12,356 infant deaths (routine data) | Increase in all-cause mortality by 4.4% (95%CI = −0.3, 9.2) per 5.6 °C increase temperature (no threshold presented). For stratified analysis; all-cause mortality in black race/ethnic group: 13.3% (95%CI = 0.6, 27.6). |
| Schinasi (2020) [15] | Case-crossover | Philadelphia, USA, 2000–2015 | Humid, subtropical climate. Mean dry bulb temperature 23.3 °C in warm season | Minimum daily temperature in warm season. Lag 0–3 days | Time-stratified case-crossover | 1522 all-cause infant deaths (routine data) | OR comparing 23.9 °C and 26.1 °C with 4.4 °C were 2.1 (95%CI = 1.2, 3.6) and 2.6 (95%CI = 1.3, 5.0), respectively. Risk of infant mortality increased by 22.4% (95%CI = 5.0, 42.6) for every 1 °C increase in temperature above 23.9 °C. No evidence of effect modification. |
| Son (2017) [36] | Retrospective cohort | 7 cities in South Korea, 2004–2007 | Climate varies across cities. Average 13.0 °C–14.8 °C. | Mean daily temperature averaged 2 weeks before death | Cox proportional hazards model | 557 all-cause infant mortality and SIDS (routine data) | HR for 1 °C increase in temperature during 2 weeks before death; 1.51 (95%CI = 1.45, 1.56) for total mortality and 1.50 (95%CI = 1.35, 1.66) for SIDS. No evidence of effect modification. |
| Basagaña (2011) [37] | Case-crossover | Catalonia, Spain, 1983–2006 | Mediterranean climate. Average maximum temperature 19.9 °C–27.4 °C. 95th percentile of maximum temperature in warm season was 27.3 °C–38.0 °C | Maximum daily temperature during warm season over 95th percentile. Lag 0–6 days | Time-stratified case-crossover | 3144 deaths on hot days (routine data) | RR 1.25 (95%CI = 1.02, 1.53) on hot day as compared to non-hot day. |
| Fouillet (2006) [34] | Heat episode analysis | France, August 2003 | Temperate oceanic climate. During heatwave, temperature exceeded 35° for at least 9 days in most French departments | Daily minimum and maximum temperatures for very hot days | Excess mortality (observed over expected deaths) | Excess mortality in infant population (0.4 million) (routine data) | Excess of 25 deaths in male infants; mortality ratio 1.3 (95%CI = 1.0, 1.6) of observed over expected deaths during same time period. No excess mortality observed in females. |
| Diaz (2004) [38] | Retrospective cohort | Madrid, Spain, 1986–1997 | Mediterranean climate. Mean maximum temperature 19.7 °C. | Maximum, minimum, and temperature in cold wave. Lag 0–7 days | Poisson regression models | Infant mortality (sample size not provided for this age group) (routine data) | 17.4% of deaths are attributable to cold wave. RR 1.21 (95%CI = 1.10, 1.32) per 1 °C, below 6 °C, at lag 4 days. |
| Karlsson (2020) [32] | Retrospective cohort | Northern Sweden 1860 –1899 | Sub-artic climate. Mean monthly temperatures 14.8 °C–15 °C | Mean daily temperature. No lags. | Time-event binomial regression model | 330 neonatal deaths (parish registers) | Temperature at and after birth not associated with increased risk of neonatal mortality for whole study population. Sami infants had a higher mortality risk than winter-born non-Sami infants with lower temperatures on day of birth, HR 1.46 (95%CI = 1.07, 2.01). |
| Scalone (2018) [33] | Retrospective cohort | Northern Italy, 1820–1900 | Prolonged rainy and dry periods with frequent violent weather events. Mean temperatures 1.2 °C–20.7 °C | Minimum daily temperature. No lag. | Multivariate statistical analysis, using event-history techniques | 175 neonatal deaths (parish registers) | Temperature at birth had a significant effect on neonatal mortality; RR 0.911 SE 0.028, p = 0.003; 9% decrease in mortality for each unit increment in temperature at birth. Daily temperature was not associated with increased neonatal mortality RR 1.031 SE 0.928 p = 0.255. Landless rural labourers were at a higher risk for neonatal mortality related to temperature at birth as compared to sharecroppers and farmers during the 1860–1900 period: RR 0.830 SE 0.068 p = 0.023 |
| SIDS | |||||||
| Jhun (2017) [39] | Case-crossover | 210 cities in USA 1972–2006 | 8 climate clusters were created given variability across different cities | Mean temperature. Lag 0–2 days | Time-stratified case-crossover | 60,364 SIDS cases (routine data. ICD 8–795.0, ICD 9–798.0 and ICD 10-R95.0) | 8.6% (95%CI = 3.6, 13.8) increase in SIDS risk for 5.6 °C increase in temperature. 3.1% (95% CI = −5.0, −1.3) decrease in the winter. Summer risks were greater among black infants 18.5% (95%CI = 9.3, 28.5) compared to white infants 3.6% (95%CI = −2.3, 9.9) |
| Auger (2015) [40] | Case-crossover | Montreal, Canada1981–2010 | Continental climate with hot summers and cold winters. Maximum temperatures ranged from −1.5 °C to 33.8 °C on days before SIDS occurred. | Maximum temperature during warm months. Lag 0–2 days | Time-stratified case-crossover | 196 SIDS cases (routine data) | Same-day maximum daily temperature of 24 °C, 27 °C and 30 °C when compared to 20 °C increased the odds of SIDS by 1.41 (95%CI = 1.17, 1.69), 2.12 (95%CI = 1.43, 3.14) and 3.18 (95%CI = 1.76, 5.77), respectively. |
| Waldhoer (2017) [41] | Case-crossover | Vienna, Austria1984–2014 | Continental climate. Mean maximum temperatures on day before and day of SIDS 14.4 °C–28.9 °C | Maximum daily temperature. Lag 0–1 days | Time-stratified case-crossover | 187 SIDS cases (routine data. ICD 10-R95.0, ICD 9–798.0 and mentioned autopsy) | OR for SIDS at same day temperatures of 24 °C, 27 °C and 30 °C compared to 20 °C were 1.05 (95%CI = 0.87, 1.27), 1.13 (95%CI = 0.76, 1.68), and 1.23 (95%CI = 0.67, 2.29), respectively. |
| Scheers-Masters (2004) [42] | Retrospective cohort | Arkansas, Georgia, Kansas and Missouri, USA1980 | Temperate climate | Daily average and maximum temperatures | Chi-squared test for trend. Spearman’s rank correlation coefficient | 111 SIDS cases (ICD 9–79.8) and heat-related mortality (ICD 9–900: Death due to excessive heat due to weather conditions) | No increase in SIDS rate with increasing average (p = 0.713) and maximum temperature (p = 0.362). |
| Chang (2013) [43] | Case-control | Taiwan 1994–2003 | Temperate climate | Daily maximum temperature categorised into percentiles | Log-liner model | 1671 SIDS cases (routine data, ICD 9–789) | Risk of SIDS at the lowest percentile <5th (9.2–14.2 °C) compared to 45th–55th percentile (21.9–23.3 °C) is 2.10 (95%CI = 1.67, 2.64). Daily mean temperature in 85th–95th percentile (26.4–27.3 °C) and >95th percentile (27.3–33.2 °C) associated with reduced risk of SIDS 0.60 (95%CI = 0.46, 0.79) and 0.61 (95%CI = 0.50, 0.75), respectively. |
CI–confidence interval; OR—odds ratio; HR—hazard ratio; RR—relative risk; SE—standard error; SIDS—sudden infant death syndrome; lag—effects of temperature may reflect exposure on the preceding days. 
Cold exposure.