Temperature and neonatal mortality in California, 1999-2007

摘要

Background: Temperature and mortality among the elderly has been widely studied. Infants have been far less researched but also lack thermoregulatory response to heat exposure. Neonates up to 28 days following birth represent the most vulnerable infancy period. Aim: To examine the association between mean daily apparent temperature, a combination of temperature and humidity, and neonatal deaths. Methods:We applied the time-stratified case-crossover study design to neonatal deaths reported by the California Vital Records occurring during the warm season of May through October from 1999 through 2007. The study population included 6,564 cases residing within twenty kilometers of meteorologic monitors. We considered possible effect modification by region, cause of death, and race/ethnic group, and potential confounding by air pollutants. Results: For all-cause mortality, coastal areas were more impacted than non-coastal areas for most causes of death (excess risk 7.12% per 10°F same-day apparent temperature; 95% confidence interval [CI]: -9.82, 24.34 in coastal areas versus 0.49%; -5.60, 6.63 in non-coastal areas). The most notable significant positive association was found for circulatory causes in coastal areas (234.52%; 46.25, 456.66), while respiratory diseases and short gestation duration also had positive impacts. Temperature effects appeared to be greatest for Blacks (11.06%; -3.44, 25.77) for all-cause mortality, although risk varied by race/ethnicity and disease subgroup. Asian neonates, for example, had a significant association with deaths from respiratory causes (136.69%; 19.43, 267.44). Risks remained independent of air pollutants. Conclusions:High temperatures were associated with an increase in neonatal deaths. Region and race/ethnicity modified the association.