Incidence and seasonality of hypothermia among newborns in southern Nepal

Abstract

Objective: To quantify incidence, age distribution, and seasonality of neonatal hypothermia among a large population cohort.

Design: Longitudinal cohort study.

Setting: Sarlahi, Nepal.

Participants: A total of 23 240 newborns born between September 2, 2002, and February 1, 2006. Main Exposures Community-based workers recorded axillary temperature on days 1 through 4, 6, 8, 10, 12, 14, 21, and 28 (213 636 total measurements).

Main outcome measures: Regression smoothing was used to describe axillary temperature patterns during the newborn period. Hypothermia incidence in the first day, week, and month were estimated using standard cutoffs. Ambient temperatures allowed comparison of mild hypothermia (36.0 degrees C to <36.5 degrees C) and moderate or severe hypothermia (<36.0 degrees C) incidence over mean ambient temperature quintiles.

Results: Measurements lower than 36.5 degrees C were observed in 21 459 babies (92.3%); half (48.6%) had moderate or severe hypothermia, and risk peaked in the first 24 to 72 hours of life. Risk of moderate or severe hypothermia increased by 41.3% (95% confidence interval, 40.0%-42.7%) for every 5 degrees C decrease in average ambient temperature. Relative to the highest quintile, risk was 4.03 (95% confidence interval, 3.77-4.30) times higher among babies exposed to the lowest quintile of average ambient temperature. In the hot season, one-fifth of the babies (18.2%) were observed below the moderate hypothermia cutoff.

Conclusions: Mild or moderate hypothermia was nearly universal, with substantially higher risk in the cold season. However, incidence in the hot season was also high; thus, year-round thermal care promotion is required. Research on community, household, and caretaker practices associated with hypothermia can guide behavioral interventions to reduce risk.

Figures

Figure 1

Locally weighted regression smoother (LWS) and median/IQR of axillary temperatures during the first 10 days of life

Figure 2

Proportion of infants meeting WHO definitions for mild, moderate, or any hypothermia, by age* *Estimates are located at the mid-point of each 24-hour interval

Figure 3

Seasonality of hypothermia: Locally weighted regression curves for daily proportion of axillary temperatures measures * Predictions at the extreme end of the curves are skewed due to progressively fewer estimates contributing to the regression estimate at those points.