WEDNESDAY, May 21 (HealthDay News) -- At least some of the biological risk for childhood asthma and allergies traces back to the womb, new research suggests.

Both the order of birth and even the way a baby is delivered have a significant impact on the long-term strength of a child's allergic defenses, scientists say.

The findings were presented Wednesday during the American Thoracic Society's International Conference, in Toronto.

At the meeting, one team of scientists said it had evidence indicating that when a specific genetic marker for allergic and asthmatic development is present among a first-born child, it appears to raise the risk for allergic conditions as far as 10 years down the road. However, when the exact same marker is present in a family's second or third child, the gene seems to have exactly the opposite effect -- actually lowering such risk.

"This is the first time it has been demonstrated that birth order can affect the behavior of genes related to asthma and allergies, and that birth order can therefore affect the risk for developing one or the other," said study author Dr. Wilfried Karmaus, a professor in the department of epidemiology and biostatistics at the University of South Carolina in Columbia.

On a second front, another team of researchers suggested that regulatory cells associated with proper immune function may be impaired in babies delivered by Caesarean section.

"We found a dysfunctional cellular response in the normally protective immune system among C-section babies," observed Dr. Ngoc Ly, an assistant professor of pediatrics at the University of California at San Francisco. "And although more work needs to be done to follow how long this response might endure, we think this disrupted immune pathway may influence the development of asthma later on."

To explore the relationship between birth order and asthma/allergy risk, Karmaus and his team tracked more than 1,200 newborns from Great Britain's Isle of Wight.

After recording birth orders, the researchers tested each newborns allergic status by examining indicators present in umbilical cord blood. As well, they conducted standard skin prick allergy tests at both age 4 and age 10.

The authors found that among firstborn children, the presence of a particular gene strain -- known as the IL-13 gene variant -- was associated with a higher risk for having an "allergic response." This link continued to persist a decade later.

By contrast, among second or later-born children no such association between IL-13 and higher risk was found. In fact, the role of IL-13 seemed to "switch over" to that of a risk protector.

"The fetus is, in effect, a foreign body," noted Karmaus. "And a foreign body can be exposed to a lot of immune arousal or not, depending. So we think that something during pregnancy -- probably the immune system of the mother -- stimulates the IL-13 gene to act differently, depending on birth order. We haven't shown how this works yet, but that's the idea."

Karmaus suggested that the finding could theoretically lead to the crafting of interventions -- perhaps therapeutic, perhaps simply lifestyle changes -- which could reduce the allergic response risk for firstborns.

Meanwhile, Ly and her colleagues explored similar risks associated with Caesarean sections by analyzing the cellular immune regulatory activity present (in the form of so-called treg cells) in the umbilical cord blood of 50 babies born by Caesarean and 68 babies delivered vaginally. All the babies had a least one parent with allergies and/or asthma.

The authors found that among C-section babies, treg cells were more likely to fail to operate properly, raising the risk for the early onset of immune system disruption. This, in turn, may increase the likelihood that a child could grow up to develop an allergy or asthma.

Ly and her team said that the suggestion that the manner of delivery could actually influence immune system development and ultimately asthma/allergy risk could be due to the fact that vaginal labor provides beneficial exposure to birth canal microbes that simply aren't available to a C-section baby.

"But still I think it's important to reiterate that while this is interesting research, it is a small study and the first of its kind," noted Ly. "So there is much more follow-up work that needs to be done to see if these newborns in fact start developing symptoms of asthma or allergies as they grow."

Approaching the root causes of asthma and allergies from yet another angle, a third team of German researchers presented findings suggesting that mothers who visit farms and drink farm milk confer a anti-allergy benefit to their future babies.

The study involved 18 farming mothers and 59 non-farming mothers. Farm-based mothers appeared to give birth to babies with better-functioning treg cells.

More information

For details on childhood asthma, visit the American Lung Association  .

SUNDAY, May 18 (HealthDay News) -- Men checking into emergency departments with pneumonia are likely to be sicker than women with the same condition and have a greater risk of dying within a year, despite receiving more aggressive medical care, a new study reports.

The findings, based on research from the University of Pittsburgh, were scheduled to be presented Tuesday at the American Thoracic Society's 2008 International Conference in Toronto. The study examined roughly an equal number of men and women with community-acquired pneumonia recruited in the emergency rooms of 28 U.S. hospitals.

The study found that the women, on average, had pneumonia symptoms for a longer time before going to the ER, but many had already received antibiotics before admission. Men, on the other hand, arrived at the hospital with more complications and had worse vital signs. Once hospitalized, men more often received antibiotics within eight hours and were twice as likely to be admitted to the ICU.

"The gender disparity on aggressiveness of hospital care is appropriate, given the fact that men tended to be significantly sicker than women," study lead Michael Reade said in a prepared statement. "But it is nevertheless insufficient to offset men's higher risk of death within the following year."

This, he said, suggests biology plays a role in survival. "The social factors we examined were not sufficient to explain the differences we observed," Reade said. "This leads us to suggest that there may be differences in genetic or inflammatory factors between men and women."

While that factor remains unknown, Reade suggests hospitals and family practitioners change their approach to men with pneumonia, because they run a greater risk of dying from it.

More information

The U.S. National Foundation for Infectious Diseases has more about pneumococcal disease  .

WEDNESDAY, May 14 (HealthDay News) -- Just a few hours of exposure to particulate matter air pollution can increase blood pressure and harm blood vessel function within 24 hours, a new study finds.

The findings may explain why air pollution can trigger a range of cardiovascular events such as heart attack, heart failure and stroke, the researchers said.

Particulate matter (PM) is a component of air pollution emitted from vehicles, power plants, and factories. It's believe that PM is the 13th leading cause of death worldwide, but the link between PM and death hasn't been well understood.

"Not everyone is equally at risk to the effects of poor air quality," researcher Robert Brook, an assistant professor of medicine, division of cardiovascular medicine, University of Michigan, said in a prepared statement.

"Yet, as traffic worsens and millions of vulnerable people are exposed to PM, it is incumbent upon us to understand how and why people are affected so that we can take steps to limit our personal exposure -- and consider making broader changes to the public agenda to control air pollution," Brook said.

In the study, researchers looked at adults living in Toronto and Ann Arbor, Mich.

In Toronto, 30 adults, aged 18 to 50, were exposed for two hours to concentrated ambient PM (CAPS alone), CAPS and ozone, ozone alone, or filtered air. Exposure to air pollution that contains PM (CAP or CAP and ozone) resulted in an average diastolic blood pressure increase of 3.6 mm/Hg. Blood vessel function was impaired 24 hours after (but not immediately after) all exposures to all exposures containing PM, but not ozone alone.

In Ann Arbor, 50 adults were pre-treated with either the antioxidant vitamin C -- which blocks the vasoconstrictor hormone endothelin (bosentan) -- or placebo. Diastolic blood pressure increased between 2.5 and 4.0 mm/Hg during all exposures. However, blood pressure function was not impaired at any time after all exposures, and blood pressure returned to normal within 10 minutes after exposure.

The fact that vitamin C didn't block the blood pressure response suggests that it's likely caused by a sudden increase in sympathetic nervous system activity.

The findings confirm that PM, not ozone, is responsible for the rapid increase in diastolic blood pressure and that this occurs only during actual inhalation of PM. The research also confirms that PM impairs blood vessel function one day after exposure. However, this blood vessel function response occurred only in Toronto, which suggests that the composition of PM or its source may play a role in determining that kind of response, the researchers said.

The study was expected to be presented Wednesday at the American Society of Hypertension annual meeting, in New Orleans.

"These findings are a springboard for further study that will specifically determine how the sympathetic nervous system responds and to what types of particles in air pollution," Brook said. "But this glimpse helps us determine the triggers behind a range of CV events -- some deadly. Learning how this dangerous cascade starts can help the medical and public health community make advances toward limiting their impact in the future."

More information

The American Academy of Family Physicians has more about air pollution and health  .