In a longitudinal, population based study, overnight temperature recordings were made in the bedrooms of 152 babies aged 3-18 weeks and the insulation provided by their bedclothing was assessed. Outdoor temperatures for the study nights were also available.Parents applied more insulation on colder nights with lower bedroom temperatures than on warmer nights (mean 8.5 tog at 15°C minimum bedroom temperature falling to 4-0 tog at 25°C). For a particular temperature they also applied 2 tog more insulation in winter than in summer.The amounts ofbedclothing used in the home were compared with insulation levels predicted to achieve thermoneutrality over a similar range of environmental temperature from heat balance studies in young infants. They corresponded closely.The The first was a descriptive study of what was actually happening in our community. It was undertaken by measuring bedroom temperatures in babies' homes and by discovering the type and amount of clothing and bedding that babies were sleeping under, throughout the year and longitudinally over the first few months of life. In contrast the second study was carried out in a laboratory environment using a series of heat balance measurements on a smaller number of babies to determine how much insulation was required to achieve thermoneutrality over a range of environmental temperatures comparable to those in the home. Methods COMMUNITY METHODS

Sequential recordings were made in the first five months after birth of metabolic rate, environmental temperature, and body temperature during sleep at home in 17 infants, each with an older sibling. Further recordings were made whenever an older sibling developed an upper respiratory tract infection (URTI), again four to six days later, and again two weeks later, aiming to achieve recordings before, during, and after an URTI in the infant. The temperature of the room and wrapping of the infant were determined according to their usual practice by the parents.Parents added appropriate wrapping to achieve thermal neutrality based on our calculated values and the measured oxygen consumption.In five of the six infants who developed an URTI in the first three months after birth there was no change or a decrease in metabolic rate at the time of the infection; for infants older than 3 months the metabolic rate increased in three of the five episodes recorded. Peripheral skin temperature decreased at the time of URTI at all ages, though in the older infants it usually increased in parallel with rectal temperature during the latter part of the night, when pyrexia was most common.Infants thus respond to URTI by heat conservation. In the younger infants the lower metabolic rate and the further decrease in this rate with URTI means that fever is rare, and their temperature may decrease on infection. In the older infants the increase in metabolic rate (from an already higher baseline) may result in fever. These differences may contribute to the increased vulnerability of the older infants to heat stress, particularly at the time of acute viral infections. (Arch Dis Child 1994; 70: 187-191) Thermal stress has been shown to be associated with an increased risk of sudden infant death syndrome (SIDS) in a number of anecdotal reports and in two case-control studies.' 2 Although the mechanism of such an association remains unclear, the reported effects of the thermal environment on respiratory pattern suggest that, at least in some subjects, the mechanism may involve an interaction between thermoregulation and respiratory control.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 7The change...

No abstract