The research was lead by Dr. Krishnan Bhaskaran of the London School of Hygiene and Tropical Medicine in the UK. He and his team note in their report that several studies have linked changes in temperature to increases in deaths due to any cause, as well as heart disease mortality.

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

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

On average, cold temperatures seemed to have a greater effect on heart attack risk in areas that were warmer, 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.

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

"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 researcher said that the evidence from the pollution studies was less clear-cut, but overall suggested that the risk of heart attack increases with levels of several different pollutants. He also noted that 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.

There also a note from Professor David E. Newby of the University of Edinburgh and colleagues accompanying this study. They said that efforts to control air pollution are likely to help reduce carbon dioxide emissions as well. This effort possibly helping to reduce the effects of climate change down the road.


Source: Dirty air, heat, cold may all trigger heart attacks