SAN DIEGO, April 26--New findings on breastfeeding and asthma, obesity and asthma and snoring and high blood pressure in pregnancy were discussed here today by an expert panel at the American Lung Association/American Thoracic Society International Conference.
Breastfeeding and Asthma
Children who are exclusively breastfed for at least the first four
months of life have a substantial reduction in the risk of developing asthma by
age 6, suggests a study presented at the conference. The study of 2,834
Australian children found that the introduction of milk other than breast milk
before four months of age was a significant risk factor for asthma in children.
Wendy Oddy MPH, in work for her Ph.D at the TVW Telethon Institute for Child
Health in West Perth, Western Australia, found that compared with children who
were exclusively breastfed for the first four months of life, children who were
not breastfed exclusively were 27% more likely to have doctor-diagnosed asthma
by age six; 44% more likely to wheeze three or more times since the age of 1;
41% more likely to have wheezed in the last 12 months; and 74% more likely to
have sleep disturbance due to wheeze within the last 12 months.
Dr. Oddy noted that asthma is the leading cause of hospitalization in American and Australian children, and the prevalence of is asthma increasing in both countries. In Australia, while nearly 90% of babies are breastfed when they leave the hospital, by age 3 months half are no longer exclusively breastfeeding. In the United States, even fewer 3-month-olds are exclusively breastfed, she said. She echoed the World Health Organization recommendation that, if possible, mothers should exclusively breastfeed for at least the first 4 to 6 months of a baby's life.
"The findings of this study are important for the prevention of asthma in children," Oddy said. There are several possible reasons for the findings, she noted. "In the past year or two, breast milk has been shown to be a bioactive, live fluid filled with proteins and lipids so essential for developing infants," she said. "Babies need as much help as they can get in developing their immune system and organs. Their mother's milk gives them the very best protective immunological factors, which are difficult to include in formula."
Oddy said that breast milk transmits immunity from the mother to baby, and can lead to enhanced tolerance to infection, which increase chances of an infant's survival. "Because asthma is a disease of inflammation, these processes occurring very early in life may affect an individual's health well into childhood and beyond," she said. "My research has shown that this is occurring, with protection against asthma and allergy from exclusive breastfeeding (and no introduction of other formula or milk) extending into childhood."
Obesity and Asthma
Obesity may increase the risk of asthma in children, a study presented
at the conference suggests. Researchers studying 16,862 children of female
nurses found that the most overweight children had approximately twice the risk
of asthma compared with the thinnest boys, and the most overweight girls had 1.5
times the risk of asthma compared with the thinnest children. The study, which
included boys and girls ages 9 to 14, was conducted by Carlos A. Camargo, Jr.,
M.D., Dr.P.H. of Brigham and Women's Hospital. Last year, Dr. Camargo presented
a study at the American Lung Association/American Thoracic Society International
Conference using data from a study of more than 100,000 nurses that found that
the more overweight a nurse was, the greater her risk of developing asthma in
adulthood.
Obesity and asthma are both on the rise in developed nations. An estimated 14.6 million Americans, including 4.8 million children, suffer from asthma. Between 1982 and 1994, the rate of asthma rose 61%, while the rate of pediatric asthma rose 72%.
Physicians have commonly assumed that people with asthma may become overweight because their breathing problems limit their activity, according to Dr. Camargo. The new study suggests that the obesity precedes the development of asthma.
"This study suggests that obesity may explain some of the increase in asthma in Western countries in the last 20 years," he said. "It's interesting to note that in wealthier countries, the poorest people are the most likely to be obese and the most likely to have asthma, supporting the plausibility of the relationship between the two conditions."
Although very little research has yet been done to examine how obesity might lead to asthma, Dr. Camargo said it is possible that being overweight somehow compresses the airways, making them smaller and therefore more reactive to cats and other common asthma triggers.
The researchers measured obesity in terms of body mass index (BMI), a measure of how overweight someone is after taking into account their height. The higher the BMI the fatter the person.
Dr. Camargo plans to conduct another year of followup on the children in the study, and then will combine data from the children's and the mother's studies, to look for trends in environmental and genetic factors.
Snoring and Pre-eclampsia
Snoring, often a sign of partial airway obstruction, is associated with
high blood pressure in pregnancy, a dangerous condition known as pre-eclampsia,
according to a study presented at the conference. Pre-eclampsia is one of the
leading causes of illness and death for pregnant women and their babies.
Dr. Colin Sullivan of the University of Sydney in Australia says the study suggests that partial upper airway obstruction may be responsible for a large portion of the nighttime increase in blood pressure in pre-eclampsia, and that treatment may minimize the obstruction and improve nighttime blood pressure control in these women.
The study of 32 women with severe pre-eclampsia and 40 women with normal pregnancies found that snoring and partial upper airway obstruction occurred in all women with pre-eclampsia, with the highest blood pressures recorded in association with increasing partial airway obstruction.
In 9 of the women with pre-eclampsia, elimination of partial upper airway obstruction with nasal continuous positive airway pressure (CPAP) resulted in a marked reduction in blood pressure. CPAP is a breathing mask attached to a machine and is used during sleep to keep the airways open.
Dr. Sullivan noted that pre-eclampsia occurs in nearly 10% of all normal pregnancies, and is the major cause of admission to the hospital during pregnancy and the major cause of infant admission to the intensive care unit. He recommended that women who are admitted to the hospital with pre-eclampsia be assessed for snoring during sleep to determine if they might be helped by CPAP treatment.