Thermal insulation and SIDS-an investigation of selected 'Eastern' and 'Western' infant bedding combinations

Evaluation of the thermal insulation of clothing of infants sleeping outdoors in Northern winter

It is a common practice in Northern countries that children aged about 2 weeks to 2 years take their daytime sleep outdoors in prams in winter. The aim was to evaluate the thermal insulation of clothing of infants sleeping outdoors in winter. Clothing data of infants aged 3.5 months was collected, and sleep duration, skin and microclimate temperatures, humidity inside middle wear, air temperature and velocity of the outdoor environment were recorded during sleep taken outdoors (n = 34) and indoors (n = 33) in families' homes. The insulation of clothing ensembles was measured by using a baby-size thermal manikin, and the values were used for defining clothing insulation of the observed infants. Required clothing insulation for each condition was estimated according to ISO 11079. Clothing insulation did not correlate with ambient air temperature. The observed and required insulation of the study group was equal at about -5 °C, but overdressing existed in warmer and deficiency in thermal insulation in colder temperatures (r (s) 0.739, p < 0.001). However, even at -5 °C a slow cooling (ca. 0.012 °C/min) of mean skin temperature (T (sk)) was observed. When the difference between observed and required insulation increased, the cooling rate of T (sk) increased linearly (r (s) 0.605, p < 0.001) and the infants slept for a shorter period (r (s) 0.524, p = 0.001). The results of this study show the difficulty of adjusting systematically the optimal thermal insulation for outdoor sleeping infants during northern winter. Therefore, the necessity for guidelines is obvious. The study provides information for adequate cold protection of infants sleeping in cold conditions.

Association of dopamine transporter and monoamine oxidase molecular polymorphisms with sudden infant death syndrome and stillbirth: new insights into the serotonin hypothesis

Recent findings demonstrated the role of neurotransmitters in the aetiopathogenesis of sudden unexpected deaths in infancy. Although genes involved in serotonin metabolism have been proposed as risk factors for sudden infant death syndrome (SIDS), the contribution of additional neurotransmitters and genes different from the serotonin transporter (SLC6A4, 5-HTT) has not been investigated. Considering the common metabolic pathway and synergism between dopamine and serotonin, the role of dopamine transporter (SLC6A3, DAT) and monoamine oxidase A (MAOA) genes in SIDS and stillbirth (sudden intrauterine unexplained death, SIUD) was investigated. Genotypes and allelic frequencies of DAT and MAOA were determined in 20 SIDS and five stillbirth cases and compared with 150 controls. No association was found between DAT polymorphisms and SIDS either at genotype (P = 0.64) or allelic (P = 0.86) level; however, a highly significant association was found between MAOA genotypes (P = 0.047) and alleles (P = 0.002) regulating different expression patterns (3R/3R vs 3.5R/3.5R + 4R/4R) in SIDS + SIUD and controls. Analysis of combined 5-HTTLPR (serotonin transporter linked polymorphic region)/MAOA genotypes revealed that frequency of L/L-4R/4R genotype combination was eightfold higher in SIDS + SIUD than in controls (P < 0.001). Findings are discussed considering the metabolic association among DAT, 5-HTT and MAOA with special emphasis on the linked action of 5-HTT/MAOA in regulating serotonin metabolism of SIDS and SIUD infants.

Genes regulating the serotonin metabolic pathway in the brain stem and their role in the etiopathogenesis of the sudden infant death syndrome

Genotypes and allelic frequencies of TPH2, 5-HTTLPR, the 5-HTT (SLC6A4) intron 2 variable-number tandem repeat (VNTR) region, and the MAOA VNTR region were determined in brain-stem samples of 20 "genuine" SIDS cases and compared with results obtained from 150 healthy controls. The SNP G1463A responsible for 80% functionality loss of TPH2 (tryptophan hydroxylase 2) was not detected, neither in SIDS infants nor in the controls. In contrast, a strict relation was found between the 5-HTTLPR genotype and its allelic frequencies with SIDS cases. The L/L genotype and the long allele (L) of the promoter region of the serotonin transporter were significantly associated (likelihood ratio (LR) test, p<0.001) with the syndrome (L/L, 60% SIDS vs 14% controls; L, 80% SIDS vs 42.6% controls). Polymorphisms of the intron 2 VNTR of the same gene showed a trend for significant differences between genotypes 10/10 and 12/12 (LR test, p=0.068), with the L-12 haplotype being almost twofold in SIDS (44.5%) with respect to controls (23.4%). Differences were even higher considering the genotype combination L/L-12/12 (20% SIDS vs 2.6%), and variations among categories were statistically highly significant (p<0.001). Although additional differences were observed in the frequency of the MAOA (monoamine oxidase A) VNTR genotype 3R/3R between SIDS and controls (respectively 15% vs 26%), the results were not supported by statistical significance. Molecular polymorphisms are discussed considering their functional role in regulating serotonin synthesis (TPH2), neuronal reuptake (5-HTTLPR and 5-HTT intron 2), and catabolism (MAOA) in the nervous system of Italian SIDS infants. Comparisons are made with previous data obtained in different ethnic groups.

Is the mattress important in helping babies keep warm?--Paradoxical effects of a sleeping surface with negligible thermal resistance

BACKGROUND

Heavy wrapping and head covering are risk factors for Sudden Infant Death Syndrome. A new mattress construction, PurFlo, has extremely low thermal resistance, and when used with an infant sleeping bag minimizes the risk of head covering.

AIM

To investigate the thermal balance and metabolic rate of infants sleeping on a conventional mattress or a Purflo mattress in infant sleeping bags.

METHODS

A longitudinal study of thermal balance of infants during day-time sleep on both mattress types in thermoneutral and cool conditions at ages 3 weeks (n = 24), 3 months (n = 22) and 5 months (n = 18).

RESULTS

In thermoneutral conditions axillary temperatures in quiet sleep were lower on the conventional mattress than on the PurFlo mattress (p < 0.05, Wilcoxon test). On lowering room temperature to 15-16 degrees C axillary temperatures fell, particularly in the older babies, and at each age were lower on the conventional mattress than the Purflo (differences 0.14-0.72 degrees C, p < 0.05, Wilcoxon test).

CONCLUSION

In both thermoneutral and cool conditions, infant temperatures were higher on the PurFlo than the conventional mattress. The more deformable surface of the PurFlo mattress may lead to more effective insulation by the sleeping bag despite a lack of mattress insulation.