A new study has showed that chronic stress alters gene activity in immune cells before they reach the bloodstream.

With these changes, the cells are primed to fight an infection or trauma that doesn't actually exist, leading to an overabundance of the inflammation that is linked to many health problems.

Ohio State University scientists made and their colleagues from other institutions, testing blood samples from humans living in poor socioeconomic conditions, found that similarly primed immune cells were present in these chronically stressed people as well.

Co-lead author John Sheridan, professor of oral biology in the College of Dentistry and associate director of Ohio State's Institute for Behavioral Medicine Research (IBMR),sa di that the cells share many of the same characteristics in terms of their response to stress.

He said that there is a stress-induced alteration in the bone marrow in both our mouse model and in chronically stressed humans that selects for a cell that's going to be pro-inflammatory.

Sheridan and colleagues have been studying the same mouse model for a decade to reveal how chronic stress - and specifically stress associated with social defeat - changes the brain and body in ways that affect behavior and health.

The mice are repeatedly subjected to stress that might resemble a person's response to persistent life stressors. In this model, male mice living together are given time to establish a hierarchy, and then an aggressive male is added to the group for two hours at a time.

This elicits a "fight or flight" response in the resident mice as they are repeatedly defeated by the intruder.

Under normal conditions, the bone marrow in animals and humans is making and releasing billions of red blood cells every day, as well as a variety of white blood cells that constitute the immune system.

In this work, the researchers compared cells circulating in the blood of mice that had experienced repeated social defeat to cells from control mice that were not stressed. The stressed mice had an average fourfold increase in the frequency of immune cells in their blood and spleen compared to the normal mice.

The study has been published in the journal Proceedings of the National Academy of Sciences.

Researchers have showed that the decline in brain function in normal aging is influenced by genes.

Senior author John Blangero, Ph.D., a Texas Biomed geneticist, said that identification of genes associated with brain aging should improve our understanding of the biological processes that govern normal age-related decline.

In large pedigrees including 1,129 people aged 18 to 83, the scientists documented profound aging effects from young adulthood to old age, on neurocognitive ability and brain white matter measures. White matter actively affects how the brain learns and functions.

Genetic material shared amongst biological relatives appears to predict the observed changes in brain function with age.

Blangero said that the use of large human pedigrees provides a powerful resource for measuring how genetic factors change with age.

By applying a sophisticated analysis, the scientists demonstrated a heritable basis for neurocognitive deterioration with age that could be attributed to genetic factors. Similarly, decreasing white matter integrity with age was influenced by genes.

The investigators further demonstrated that different sets of genes are responsible for these two biological aging processes.

Women exposed to even low levels of urban air pollution during pregnancy may be at heightened risk of having a low-birth weight baby, according to a review of evidence from Europe.

Based on data for more than 74,000 women in 12 European countries over a 15-year period, researchers say that if pollution levels were lowered to limits set by the World Health Organization (WHO), 22 percent of cases of low birth weight would be avoided.

"This is similar to the number of cases that would be prevented by cessation of maternal smoking during pregnancy in this European population," said lead author Dr. Marie Pedersen from the Centre for Research in Environmental Epidemiology in Barcelona, Spain.

Babies who weigh less than 5.5 pounds at birth are at increased risk of respiratory problems in childhood, as well as other disorders later in life.

Pedersen's team looked at 14 studies of pregnant women who had a child at full term between 1994 and 2011. She told Reuters Health the researchers specifically focused on areas "where people live" - as opposed to industrial locations - and selected cities that are much smaller, with less dense traffic than the average American city.

The researchers were able to obtain detailed birth records, including home addresses during pregnancy, infant birth weight and gestational age and sex, from maternal health centers in Scandinavia, Western Europe, England, Lithuania and Greece.

They also developed their own intensive air-monitoring network, sending teams to residential areas in the study and measuring pollution levels over three different seasons. Pedersen and her colleagues also used data from air monitoring stations and combined it with information on traffic density and land use.

When they looked at women's exposure during pregnancy to the type of fine particles in vehicle exhaust and some industrial air pollution, they found that for every increase of 5 micrograms per cubic meter of air, the risk of low birth weight at term rises by 18 percent.

In addition to the babies' weight at birth, the study looked at their head circumference because of its potential effect on brain development, according to Pedersen. They found reductions in the head size of babies whose mothers were exposed to average small particle concentrations of more than 15 micrograms per square meter.

The researchers took into account factors like maternal smoking, age, height and weight and education, and still concluded that all air pollutants, especially fine particulates, as well as traffic density, were tied to an increased risk of low birth weight and reduced average head circumference at birth.

Among the women studied, the average exposure levels to fine particulates during pregnancy ranged from less than 10 micrograms per cubic meter of air to nearly 30 micrograms.

The results were published in The Lancet Respiratory Medicine.

Current European Union air quality standards recommend limiting a person's average fine particulate exposure over the course of a year to no more than 25 micrograms per cubic meter.

The United States Environmental Protection Agency (EPA) sets an upper limit for a 24-hour period of 35 micrograms per cubic meter, but in 2013 EPA lowered the annual exposure limit to 12 micrograms per cubic meter. The WHO standard is no more than an average of 10 micrograms per cubic meter.

If the women in the study had all been exposed to only the WHO standard for particulates, Pedersen said, 145 cases of low birth weight among 50,151 babies would have been prevented.

"In setting new more stringent standards for ambient air pollution, the United States has taken a leadership role," said Tracey Woodruff, director of the Program on Reproductive Health and the Environment at the University of California, San Francisco. But most cities in the United States are currently out of compliance.

"While Europe has better regulations on toxic chemicals, the United States has been a leader in this area, and it could be that this study will be more evidence for the Europeans to take action," added Woodruff, who has researched the effects of pollution exposure during pregnancy.

Pedersen said pregnant women worldwide are exposed to air pollution at similar or even higher concentrations than those found in her group's study, and the results "provide a clear message to policymakers to improve the quality of the air we all share."

"We need cars and we need to heat our homes, but I think it is possible to develop cleaner cities," she said. "It's a change that can happen and I really hope it will, because there are so many bad health outcomes related to air pollution."

Dr. Jonathan Grigg from Queen Mary University of London, UK, said, "'acceptable' levels (of air pollution) may well need to be revised downward in the light of this and other studies."

Although this would involve weighing costs and benefits, "policy makers also have to take a precautionary approach when considering children's health," said Grigg, who wrote a commentary accompanying Pedersen's study and is co-chair of the Royal College of Physicians Working Party on air quality and life effects.

Grigg, a London resident, told Reuters Health in an email that he would like to place cell-phone size personal monitors onto pregnant women to see what determines how much particulate pollution they're exposed to. That could suggest generic precautions, like avoiding walking right next to heavily used roads, that do not "either impact on lifestyle or make women feel guilty," he said.

He also suggested that policymakers take steps to reduce urban air pollution by requiring reductions in emissions by cars, taxis and buses. Development of stop/start technology to prevent idling, and requiring fuel cell power for buses, would also help.

Diet, exercise, therapy and drugs can help obese people get healthier. But weight-loss surgery does a better job of getting rid of extra pounds and treating type 2 diabetes, a new review of past studies shows.

The studies only followed people for two years. So it's possible the results would look different further down the line, the authors write.

So-called bariatric surgery, like gastric bypass or gastric banding, reduces the size of the stomach so patients can only eat small amounts of food.

Many doctors have noted the dramatic weight loss that often results. But it wasn't obvious how surgery stacks up against traditional diet and exercise strategies.

The new review included 11 studies. Each study randomly chose some obese people to have surgery and others to make diet or lifestyle changes instead, for instance. Together those studies included close to 800 people.

Participants in the bariatric surgery groups lost an average of 57 more pounds than those in the non-surgery groups. Average weight loss ranged from 45 to 100 pounds among those who had surgery.

More people who had type 2 diabetes saw their blood sugar levels fall into the normal range after surgery than after a different intervention.

"Although they try to look at a range of medical conditions, in reality the real importance is the effect of weight loss on diabetes and the relative effectiveness of non-surgical versus surgical approaches," said Dr. Paul O'Brien.

O'Brien is an obesity specialist who pioneered the Lap-Band procedure in Australia in 1994. He founded the Centre for Obesity Research and Education at Monash University in Melbourne and was not involved in the new review.

"The clear and consistent message is the bariatric surgical procedures achieve a much better outcome," O'Brien said.

Bariatric surgery will certainly help obese people with diabetes better control the disease and may put it into remission entirely, he said.

"Given that there are probably in excess of 300 million people across the world with type 2 diabetes and maybe half of these are obese, this opens up huge possibilities for better health," O'Brien told Reuters Health.

But two years isn't really enough time to judge the results. And the analysis included small numbers of studies and patients, Viktoria L. Gloy from University Hospital Basel in Switzerland and colleagues note in the journal BMJ.

Longer-term studies, cost-effectiveness studies and comparisons between different surgeries are still missing, O'Brien said.

The authors did not respond to a request for comment before deadline.

Surgery is typically recommended for people with a body mass index - a measure of weight in relation to height - of at least 40, or at least 35 if they also have co-occurring health problems such as diabetes or severe sleep apnea.

"I think an important point to consider is that most of the studies suggest that bariatric surgery combined with intensive lifestyle management is superior to lifestyle management alone," said Dr. Richdeep Gill. He is a general surgeon at the University of Alberta in Canada.

Generally people who undergo weight-loss surgery must try lifestyle changes like diet and exercise first before going under the knife. So it may not be an either/or choice for most obese people.

Gill, who studies bariatric surgery, was not involved in the review.

Patients need to be informed about the risks of surgery, he told Reuters Health.

According to the National Institutes of Health, gastric bypass surgery carries risks of allergic reactions to anesthesia, blood clots, breathing problems, heart attack, stroke or infection.

In the review, 15 percent of people in the surgery groups had anemia from low iron levels post-surgery and 8 percent needed a second operation.

It's impossible to say how serious those additional surgeries were. But second surgeries are always more difficult than the first, Gill said.

Post-surgery, patients must stick to a special diet for life and often have to avoid some common medications like aspirin and other non-steroidal anti-inflammatory drugs.

"Tackling obesity is a challenging issue, and the patient needs to be committed to their own management strategy," Gill said. Only then, with consultation of a multidisciplinary care team, will surgery be considered as an option.