Overnight deep body temperature and urinary cortisol excretion in infants from economically deprived areas

OBJECTIVES: To assess the pattern of postnatal physiological maturation in economically deprived infants by measuring the age-related changes in deep body temperature during night-time sleep. SETTING: Inner city Leicester, UK. PARTICIPANTS: Forty-eight infants aged 6-21 weeks from economically deprived areas and 87 control infants from more affluent areas. OUTCOME MEASURES: Average deep body temperature between 2 and 4 h after bedtime, overnight and early morning urinary cortisol excretion. RESULTS: Both groups showed a decline in overnight deep body temperature with age that averaged 0.030 degrees C per week (SE = 0.003). Over the age range studied, the average age-adjusted overnight temperature in the infants from deprived homes was 0.090 degrees C (SE = 0.028) higher than that for the affluent group (P = 0.001). Deprived infants had on average 51% higher overnight urinary cortisol and 80% higher morning cortisol. The differences remained when the effects of room temperature, clothing, smoking, birthweight and gestational age were taken into account. CONCLUSION: These indicators of postnatal physiological maturation suggest that infants from economically deprived homes mature less quickly. This might increase their vulnerability to illness.