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Extreme temperatures and heavy air pollution boost heart attack risk, according to a major new study.

And on days when the air is extra dirty and the temperature is unusually hot or cold, the effects are likely to be particularly bad, given that temperature and pollution seem to harm the body in different ways, Dr. Krishnan Bhaskaran of the London School of Hygiene and Tropical Medicine in the UK, the lead author of the research, told Reuters Health.

Several studies have linked changes in temperature to increases in deaths due to any cause, as well as heart disease mortality, Bhaskaran and his team note in their reports. But looking at heart attacks-not just deaths from heart disease-could offer a more accurate picture of the overall health risks of temperature changes and air pollution, they say, and might also offer clues to why they may trigger heart attack in high-risk people.

In two separate reports, the researchers reviewed 19 studies on temperature and heart attack and 26 examining air pollution and heart attack.

In the 12 temperature studies that collected winter data, eight showed short-term increases in heart attack risk with colder temperatures. Seven of the 13 studies that looked at the effects of warmer temperatures found increased heart attack risk in hotter weather.

Cold temperatures seemed to have a greater effect on heart attack risk in areas that were warmer, on average, Bhaskaran and colleagues note, suggesting that people living in colder areas may be better adapted to dips in temperature. But hot days boosted heart attack risk whether they happened in Sweden or Brazil.

In a city that normally sees 10 heart attacks a day, Bhaskaran explained, the findings show there might be an extra one to four heart attacks on the hottest or coldest days.

“There was a lot of variation in the methods and quality of the studies we reviewed, so more work is needed in this area, but we thought the results were consistent enough to suggest that these effects are real,” he added.

The evidence from the pollution studies was less clear-cut, the researcher said, but overall suggested that the risk of heart attack increases with levels of several different pollutants. Also, he noted, there appeared to be no “safe” level of air pollution at which no effect on heart attack risk was seen.

“Our findings would suggest that further lowering limits would likely further reduce the health burden associated with pollution, which is of course a desirable outcome,” he said.

Governments can also make an effort to alert at-risk people when extreme temperatures or high levels of pollution are expected, the researcher said. He noted that the UK now makes automated phone calls to people with emphysema when they are at risk due to changes in temperature; this, he said, has led to a reduction in hospital admissions for lung disease patients.

In an editorial accompanying the study, Professor David E. Newby of the University of Edinburgh and colleagues note that efforts to control air pollution are likely to help reduce carbon dioxide emissions as well, possibly helping to alleviate the effects of climate change down the road.

The self-reported health of the newly retired improves so much that most feel eight years younger, a new European study suggests.

This happy news was true of most everyone except a small minority — only 2 percent — who had experienced “ideal” conditions in their working life, anyway.

“The results really say three things: That work puts an extra burden on the health of older workers, that the effects of this extra burden are largely relieved by retirement and, finally, that both the extra burden and the relief are larger when working conditions are poor,” said Hugo Westerlund, lead author of a study published online Nov. 9 in The Lancet. “This indicates that there is a need to provide opportunities for older workers to decrease the demands in their work out of concern for their health and well-being.”

But of course, added Westerlund, who is head of epidemiology at the Stress Research Institute at Stockholm University in Sweden, “not all older workers suffer from poor perceived health. Many are indeed eminently healthy and fit for work. But sooner or later, everyone has to slow down because of old age catching up.”

Last week, the same group of researchers reported that workers slept better after retirement than before. “Sleep improves at retirement, which suggests that sleeping could be a mediator between work and perception of poor health,” Westerlund said.

This study looked at what the same 15,000 French workers, most of them men, had to say about their own health up to seven years pre-retirement and up to seven years post-retirement.

As participants got closer to retirement age, their perception of their own health declined, but went up again during the first year of retirement.

Those who reported being in poorer health declined from 19.2 percent in the year prior to retirement to 14.3 percent by the end of the first year after retiring. According to the researchers, that means post-retirement levels of poor health fell to levels last seen eight years previously.

The changes were seen in both men and women, across different occupations, and lasted through the first seven years of not punching the clock.

Workers who felt worse before retirement and had lower working conditions reported greater improvements as soon as they retired, the team found.

“Those who had low job satisfaction — a lot of burden for little satisfaction — those were the ones complaining of their health,” said Dr. Gary Kennedy, director of geriatric psychiatry at Montefiore Medical Center in New York City. “People with more authority or better education, a better sense of control over what they were doing and less demand were much less likely to complain,” he added.

“That’s not really surprising,” he said. “An old study of English civil-service workers in Britain found that those who felt they had a lot of responsibility but little control over their workplace were more likely to develop heart disease,” he added. “You can work hard but if you feel like you’re not at the mercy of a job, you still have the illusion of control. That’s an important illusion to maintain.”

A major question is whether these European findings apply to conditions in the United States.

“It’s a little bit difficult to apply directly to our workforce but … we can draw some conclusions about keeping a strong and healthy workforce through the life span,” said Angie Hochhalter, assistant professor of internal medicine at Texas A&M Health Science Center College of Medicine and research scientist in geriatrics at Scott & White in Temple, Texas.

“We know that we need strong health care but also mental services because, in [the study], those people with depression really saw a dramatic change after retirement,” she explained.

“In addition to strong systems, there’s also some degree of personal responsibility for trying to keep ourselves healthy — managing stress from work and from home, healthy eating and physical activity, and staying involved with social support,” Hochhalter added.

Workers in both the United States and Europe are likely to be affected similarly by poor working conditions, Westerlund added.

Babies who are deprived of oxygen at birth often go on to have lifetime disabilities, but research has shown that cooling infants can help prevent problems.

Now, a new study reports that the cooling actually reduces the number of brain lesions in the babies.

Oxygen starvation at birth can cause a condition called hypoxic-ischemic encephalopathy, which can be fatal. Oxygen starvation also accounts for about 20 percent of cerebral palsy cases.

An earlier study found that chilling infants who suffer from oxygen deprivation can help reduce rates of cerebral palsy and improve their motor skills later in life. In the new study, reported online Nov. 5 and in the January issue of The Lancet Neurology, researchers investigated whether MRI scans would reveal fewer cerebral lesions in infants who were cooled.

That turned out to be the case. After reviewing MRI brain scans of 131 infants, they found 30 to 40 percent fewer lesions in areas of the brain where neurological development occurs. The infants who underwent cooling were three times more likely than those who didn’t to have normal scans.

The scans also allowed doctors to predict with more than an 80 percent degree of certainty whether the infants would die or be disabled by the time they were 18 months old. The accuracy rate was 84 percent for the infants who were cooled and 81 percent for those who were not.