Long-Term Exposure to Extreme Temps Tied to Newborn Lung Function

Long-term exposure to heat and cold from the second trimester to 4 weeks after birth was associated with lung function among female newborns, according to a French population-based cohort study.

Specifically, long-term heat and cold exposure were associated with decreased functional residual capacity (FRC) and increased respiratory rate, while only long-term cold exposure was linked to lower tidal volume, reported Johanna Lepeule, PhD, of the Institute for Advanced Biosciences in La Tronche, France, and co-authors.

The effects of climate change have led to more variance in temperatures, which has the potential to impact public health, they noted in JAMA Network Open.

"Current data suggest that unusual ambient temperatures may promote or worsen respiratory diseases, such as asthma, rhinitis, or respiratory tract infections," the group wrote. "Decreased forced vital capacity and peak expiratory flow have been associated with short-term and long-term exposure to extreme temperatures in healthy children or children with asthma. During pregnancy, high diurnal temperature variations have been associated with significant increase of pneumonia diagnosis and the common cold in children."

Lepeule and team found that long-term heat exposure (24°C, or 75°F) during gestational weeks 20-35 and weeks 0-4 after delivery was associated with decreased FRC (-39.7 mL, 95% CI -68.6 to -10.7) compared with the median temperature (12°C, or 54°F), and to increased respiratory rate during gestational weeks 14-35 and the first week of life (28.0/min, 95% CI 4.2-51.9).

Long-term cold exposure (1°C, or 34°F) was associated with decreased FRC during gestational weeks 15-29 compared with the median temperature (-21.9 mL, 95% CI -42.4 to -1.3) and lower tidal volume at gestational weeks 14-35 and weeks 0-4 after delivery (-23.8 mL, 95% CI -43.1 to -4.4), as well as increased respiratory rate at gestational weeks 6-35 and weeks 0-1 after delivery (45.5/min, 95% CI 10.1-81.0).

No consistent associations were observed for male newborns or short-term exposure to cold or heat.

"Thermoregulation is compromised in pregnancy due to increased cardiovascular demands and other physiologic changes," Lepeule and colleagues wrote. "These physiologic alterations may affect lung development of the fetus, in accordance with this study's results. Direct temperature exposure during the postnatal period could act on the respiratory system as well as on risk factors (e.g., allergens) of altered lung function."

"Research must continue to better understand the long-term impact of unusual temperatures in early life and to raise awareness of health risks posed by heat and cold exposure during this period among pregnant women, mothers, and healthcare professionals," they concluded.

For this study, the researchers included 343 mother-child pairs. Median maternal age at conception was 32, and 47% of the newborns were girls. Women were recruited during pregnancy from July 2014 to July 2017. A total of 246 mothers and/or fathers held at least a master's degree.

Using the addresses of participants, the researchers measured the daytime temperature, nighttime temperature, overall temperature, and variability of temperature.

The median overall temperature during pregnancy was 12.7°C (55°F), with the highest temperatures observed in July (22.8°C, or 73°F) and the lowest in January (3°C, or 37°F).

Lepeule and team noted that their cohort size was small, and participants were fairly well educated across the board, which may limit the applicability of these results to different populations. Other limitations included the "possible spurious associations" due to numerous tests being performed.

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