Limitaciones a los poderes públicos en garantía del derecho a

Despite the overwhelming emphasis on research into the relationship between heat stress and SIDS, there is some evidence that cold stress also affects SIDS risk.

Thermal stress and SIDS in the literature almost always refers to heat stress only.

Cold stress and SIDS has been hugely under-researched compared to heat stress and SIDS.

Williams and colleagues (1996) found an association between SIDS and too little insulation. Another possible relationship between cold and SIDS is that defects in the infants thermoregulation could cause hypothermia. Dunne and colleagues (1986) published a case study of a boy in the first years of his life who had frequent episodes of hypothermia and sleep-related apnoea. Various attempts to prevent him from getting cold when he slept did not work, and he suffered several near-miss episodes of SIDS. When he was 17 months old, the episodes stopped and he subsequently suffered no long-term effects.

Goldsmith and colleagues (1991) suggest that infants who become too cold in the winter months are subjected to an under-recognised cause of SIDS. Lloyd (1986) suggested that environmental cold can cause death through other mechanisms than hypothermia, and argued that some of the increase in SIDS observed during the winter may be due to undiagnosed pulmonary hypotension with apnoeic episodes. Cardiovascular changes could be a factor in cold stress and SIDS, as discussed above. Furthermore, cold depresses the immune system and leaves the body less able to fight off pathogens, so cold-stressed infants may suffer more frequent infections, which are also linked to SIDS. There have been several reports of SIDS victims having had respiratory infections in the weeks prior to their death (Bajanowski 2007; Fleming and colleagues 2006; McKenna and colleagues 1996; Moloney and colleagues 1999). Evidence for the link between the colder temperatures and SIDS is extremely scarce, however. The over-emphasis on

95 protecting infants from heat stress might unintentionally be putting an unknown number of infants at risk of SIDS due to cold stress. Efforts to eliminate all sources of thermal stress, including stress caused by both heat and cold, would ultimately be a more sensible approach, one which is largely congruent with the actual infant care practices of mothers in cultures influenced by humoral beliefs.

3.5 Conclusion

The thermoregulation of an infant is complex. There are many intrinsic and extrinsic factors to consider in how the infant controls its temperature and responds to thermal stress. There are also many individual differences that dictate

thermoregulation as well as thermal comfort. Different infants will express thermal discomfort at varying levels of thermal stress, which partly influences the types of thermal care they receive from their caregivers. How thermal stress contribute to SIDS is equally complex, and its complexity must be adequately acknowledged when designing SIDS-prevention advice for parents that relates to thermal care of infants.

The precise mechanisms that cause SIDS are not known. It appears that a SIDS death results from a combination or succession of physiological challenges to the infant’s respiration and internal regulation, especially in infants with often unknown, subtle vulnerabilities. SIDS is the main cause of death in the UK for infants aged one month to one year, but the number of infants dying of SIDS in this context pales in comparison to the millions of infants who die from pneumonia alone in the rest of the world. Lack of resources needed to conduct post-mortem examinations, combined with a context in which infectious diseases are prevalent, makes it almost impossible to establish whether or not there is a significant incidence of SIDS deaths in lower-income countries. In the UK, the search to unravel the mysteries of SIDS is of great concern. Certain ethnic minorities in high-income countries, especially South Asian communities, have remarkably low rates of SIDS (Blackwell and colleagues 2006). South Asian infants’ slower maturation of thermoregulation, higher rates of LBW, and reported higher bedroom

temperatures would seem to put them more at risk of SIDS, but their SIDS rate is in fact exceptionally low. One of the explanations for this apparent paradox is that

96 cultural patterns of infant care among South Asian groups involve a higher degree of attentiveness through the night and day, which offer protection to infants as they undergo internal physiological challenges.

One area that seems particularly lacking in SIDS research on thermal stress is the contribution of cold stress to SIDS. Many papers refer to thermal stress but focus entirely on heat stress. Although there are only a handful of studies that examine the link between cold stress and SIDS, theoretically there is no reason for cold stress to be any less significant to SIDS than heat stress. I propose that this bias is due to cultural beliefs in the UK that focus on the dangers of heat for infants to the exclusion of dangers caused by cold. Another reason that South Asian infants in the UK could have such low SIDS rates could be because their mothers,

informed by humoral beliefs that emphasise maintaining thermal balance avoid exposing their infants to extremes of cold or heat, so protecting them from both heat and cold stress.

SIDS prevention advice regarding thermal (heat) stress usually focuses on room temperature and use of appropriate clothing and bedding for infants at night.

It has already been established that no infant will have the same thermal experience in a given environment. For example, older healthy babies may suffer heat stress in the same environmental temperatures that cause hypothermia in newborn or low birthweight infants. Estimating appropriate bedding and clothing for a given environmental temperature has proved to be especially complex, yet this complexity is vastly oversimplified when research findings are translated into public health messages regarding SIDS prevention. It is not possible to guarantee that a given amount of clothing and bedding for a given environmental temperature will protect even one infant from heat stress during the night, and it is even more inappropriate to assume that one-size-fits-all advice can be developed that applies to all infants. It may ultimately prove to be more important for individual mothers to respond to infant cues regarding thermal comfort, since infants experience extrinsic and intrinsic changes throughout the night and at different times may require assistance from his/her caregivers to maintain thermal comfort and be protected from the potential dangers of thermal stress. Human thermoregulation is

97 part physiological and part behavioural, and thus an infant’s expression of its own unique response to heat and cold stress must be considered more important than uniform assumptions about appropriate room temperatures and amounts of clothing and bedding.

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