Sudden infant death syndrome (SIDS): disordered brown fat metabolism and thermogenesis

Foster found areas with the highest incidence of SIDS in USA in 1983-1984 coincided with the highest areas recorded with the highest incidence of goitre in First World War troops (1). Reid compared the two populations described as having the highest incidence of SIDS worldwide. Both were selenium deficient areas (King County WA, USA and Canterbury, New Zealand). Besides being a selenium livestock responsive area, Canterbury school children, prior to 1925, had a 56% incidence of goitre (2-6). Brown adipose tissue (BAT) synthesises fatty acids from glucose. BAT is a major tissue in fatty acid metabolism for the generation of heat (7). BAT has the specific property of converting thyroxine (T4) to triodothyronine (T3) via Type II deiodinase enzyme. There is a many fold increase in the activity of this deiodinase in BAT after exposure of rats to sudden cold, which is greatly impaired in selenium deficient animals (7). The accepted picture of SIDS worldwide is that there is an increased incidence in infants of young smoking mothers. The incidence peaks in the second and third month of life, in winter and as latitude increases.