The report from the University of Washington School of Medicine called for a ``vigorous public campaign warning of heat stress as a preventable risk factor'' in some infant deaths. ``Although the risk of thermal stress is widely accepted abroad, it has received relatively little attention in the United States, ''said the study in the April issue of ''Pediatrics,'' published by the American Academy of Pediatrics. ``The incidence any infant death, including those diagnosed, SIDS, in the United States can likely be further reduced by educating the public against the dangers of overheating, as an integral part of the back-to-sleep campaign,'' it said.
The study concludes that deaths attributed to re-breathing could more logically be attributed to thermal stress. Still, in a program designed to reduce the risks of infant death, both thermal stress and re-breathing should have as common objectives the avoidance of prone sleeping, soft bedding, and covering the head. Excessive sweating, high room temperature, infection with fever and excessive bedclothes are factors in heat stress.
``It is possible that both thermal stress and re-breathing are interrelated co-factors of a lethal process that could lead to (death) through failure to arouse or respiratory failure,'' the study concluded. ``Defects in brain stem function from earlier injuries could increase the susceptibility to either mechanism.''
The findings contradict long-held concerns that the nutritional rigors of nursing could damage the bone health of young mothers who are still themselves growing and developing. The results of this study are important because they reassure young women that they can offer what numerous studies have shown to be the most perfect food for babies -- breast milk-- without compromising their own health. Teen moms are far less likely to nurse than are adult women, in part because of widely held misconceptions surrounding this feeding method.
In the new study, reported at the annual joint meeting of the 2001 Pediatric Academic Societies and American Academy of Pediatrics in Baltimore, Md., women who had breastfed as teenagers showed no signs of bone loss an average of nearly three years after the birth of their last child. In fact, the researchers found these women had stronger bone mineral density once they stopped breastfeeding than did moms who had children but did not nurse in their formative years. "Until now, we really weren't sure whether the bones of a breastfeeding adolescent could recover from the nutritional rigors of breastfeeding, but the results indicate that lactation may actually protect a teenager's bone health," said lead study author Caroline Chantry, UC Davis assistant professor of pediatrics. "This finding, coupled with the known health benefits both baby and mother receive from breastfeeding, clearly underscores the overall advantage for both mother and baby in choosing breastfeeding over formula."
The study of 819 white, black and Mexican women between the ages of 20 and 25 included 94 who had breastfed as teens, 151 who had babies but did not nurse them in their adolescence, 156 who had their first child as adults and 418 who were childless. The study, which accounted for such demographic and lifestyle factors known to affect bone mineral density as race, diet, weight and exercise, showed teen mothers who breastfed had 5 percent to 7 percent higher bone mineral density in all five areas of the femur studied than did their peers who did not breastfeed.
Infants who were fed more breastmilk than infant formula were at less risk for being overweight in late childhood and adolescence than those who were fed more infant formula than breastmilk, and infants who were breastfed for a longer period were at less risk than those breastfed for a shorter period, according to an article published in JAMA.
The authors used a 1996 survey of 8,186 girls and 7,155 boys age 9 to 14 who participated in the nationwide Growing Up Today Study, a cohort study of diet, activity, and growth. The children's and adolescents' mean age was 11.9, and 93.6% of them were white. Additional data came from a 1997 supplemental questionnaire sent to participants' mothers, who took part in the Nurses' Health Study II.
The 1996 survey questionnaire for child participants collected data on sex, race/ethnicity, height, weight, sexual maturity, age at menarche for girls, diet and physical activity in the past 12 months, and average time spent watching television on weekdays and weekends. The 1997 survey collected data on each child's birthweight, birth length, category of gestational age, medical conditions during childhood, and infant feeding practices. Survey questions on feeding practices relied on the mother's recollection of 1) what the infant was fed during the first 6 months of life (breastmilk, infant formula, or a combination), and 2) duration of breastfeeding (less than 1 month, 1 to 3 months, 4 to 6 months, 7 to 9 months, or more than 9 months). Additional information on the mothers' weight at birth and at certain subsequent intervals, smoking habits, dietary restraint, diet, weight history, body mass index (BMI), and physical activity levels were obtained from other studies associated with the Nurses' Health Study II.
The authors compared 1) children and adolescents fed primarily breastmilk as infants and those fed primarily infant formula, and 2) children and adolescents breastfed for 7 months or more as infants and those breastfed for 3 months or less. Overweight in children and adolescents was defined as "BMI exceeding the age- and sex-specific 95th percentile in a national sample of US children," and children and adolescents whose BMI was between the 85th and the 95th percentiles were categorized as being "at risk of overweight."
The study findings include the following:
The authors suggest two possible mechanisms to explain these findings. The first is behavioral. Infants who breastfeed naturally stop when satiated, whereas a parent feeding from a bottle may continue feeding until the contents are finished. Thus, formula-fed infants may consume more than necessary. The second mechanism could involve the serum level of insulin found in breastmilk, and the serum level's possible impact on inhibiting the development of adiposity. For these reasons, the authors find their study "consistent with the recommendations of the American Academy of Pediatrics to maintain breastfeeding for the first 12 months of life."
Gillman MW, Rifas-Shiman SL, Camargo CA, et al. 2001. Risk of overweight among adolescents who were breastfed as infants. JAMA 285(19): 2461-2467
