The thermal environment in which 3-4 month old infants sleep at home.

Abstract

SUMMARY The thermal insulation of clothing and wrapping (tog value), room temperature, and body temperature was measured for 3-4 month old infants sleeping in their home cots under conditions chosen freely by parents during a cold winter. We found that ambient temperature averaged 18-4°C when infants were put down, but fell by an average of 4-4°C during the night. Minimum room temperature correlated with outside temperature, but most rooms were heated to some degree; smaller babies were kept in warmer rooms. The tog value of clothing before putting the baby down averaged 5-1, supplemented by 9-6 tog units of wrapping in the cot-a 188% increase for a 4-40C drop in temperature.Total tog of clothing and wrapping correlated negatively with minimum room temperature; smaller born babies tended to be more heavily wrapped. Despite the large increase in insulation in the cot, most babies maintained normal body temperatures.Over the last couple of decades there has been a substantial increase in the variety of items for clothing and wrapping of babies, and a rise in the number of homes with central heating. There are few reports, however, of the thermal consequences of the way in which parents now clothe and wrap their babies. 1 Recent reports of raised core temperature in some sudden infant deaths,2 and subsequent retrospective analysis of clothing and wrapping,3 have suggested that 'over wrapping' may be a contributory factor, but is not clear how 'over wrapping' can be defined as we have no precise information about either the range of normal parental behaviour or how it affects infant thermoregulation.In this study we report data on the room temperatures to which normal 4 month old infants were exposed at home during the night, the extent to which they were clothed and wrapped, and the factors that parents took into account in deciding the appropriate combination of room heating and coverings for sleeping babies during a cold British winter. Subjects and methodsInformation on a random sample of normal, full term, singleton babies was collected at birth, and permission obtained from parents for the body temperature to be monitored for one night during sleep between the ages of 3-4 months. At this time each child was visited at home, weighed, skin fold thickness measured, and information obtained on feeding pattern and the recent health of the baby. Three thermistor probes were securely attached to the baby: (a) at the centre of the forehead; (b) on the abdomen 3 cm to the left of the umbilicus; and (c) into the rectum 5 cm from the anal margin.

Interaction between bedding and sleeping position in the sudden infant death syndrome: a population based case-control study.

“…This analysis showed that for the younger infants for whom complete data were available there was no significant difference in total thermal insulation of bedding plus clothing between the infants who had died (n=24) and the control infants (x2=0-75, p>005) whereas the prone position was associated with an increased risk of sudden unexpected infant death (x2=7 14, relative risk 4 15, 95% confidence interval 1 32 to 13 04, p<0 01). For the older infants for whom complete data were available there had been a highly significant excess of bedding and clothing on the infants who had died (n=38) compared with control infants.…”

“…4 The low incidence of the sudden infant death syndrome in Hong Kong, which has a hot, humid climate but where most infants sleep supine, has led to the suggestion that the prone position may be an important risk factor.4 Recently, Nelson et al suggested on the basis of a simple model of infant heat balance that infants sleeping in the prone position with an excess of bedding would be more likely to become hyperthermic than infants in the supine position with equal bedding. 6 We have shown an appreciable rise in oxygen consumption and carbon dioxide production (and hence heat production) between birth and 1 month of age in healthy infants.7 This higher metabolic rate is maintained until at least 3 months.…”

Thermal balance and metabolic rate during upper respiratory tract infection in infants.

“…Figure 1 shows the relation between the effective environmental temperature and the total thermal resistance of the bedding and clothing chosen by the parents (corrected for the proportion of surface area covered, as described previously) for the daytime sleep recordings.' 11 4 In the infants aged less than 3 months this decrease was less consistent and rarely more than 0 4°C, whereas for older infants the decrease was consistent and usually greater than 0 6°C. Figure 3 shows these changes with age for typical infants aged 30 and 184 days.…”

“…3 In this context the head, as the site of about 40% of heat production and up to 85% of heat loss for the infant in bed, may be particularly vulnerable to the effects of thermal stress. 4 In two studies an excess incidence of head covering was found in infants who died from SIDS compared with matched controls,5 6 and in animal studies relatively small changes in brain temperature have been shown to have potentially major effects on the control of respiration.7 Thus factors which increase the resting metabolic rate might have a significant influence on respiratory control both by a 'feed forward' effect of increased carbon dioxide production (which may directly affect respiratory drive) and by an effect on cerebral temperature, particularly under conditions (for example a prone sleeping position, head covering) in which the ability to lose heat from the head might be compromised.3 6 7 The change in metabolic rate over the first three months after birth, which, when expressed in terms of heat loss for each unit of surface area amounts to an increase of over 50%, might be expected to put infants aged 3 months at a higher risk of the adverse effects of a warm environment than younger infants.8 In the Avon study the risk of SIDS was increased by the presence of heavy wrapping only for those aged more than 70 days. '…”

Disturbed nights and 3-4 month old infants: the effects of feeding and thermal environment.

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AbstractParents completed a prospective diary of a night's sleep for 87,[3][4] month old infants at home whose body temperatures were continuously recorded. We found that about half of the babies disturbed their parents in the night.

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