Heart attack rates are highest when temperatures are below 0°C

Cold weather can trigger a heart attack, research suggests.

The life-threatening condition is more likely to occur on chilly, windy days when there is little sunshine, a study found today.

And sub-zero temperatures increase a person's risk of suffering the most serious type of heart attack by nearly 10 per cent, the research adds, according to Daily Mail.

Icy weather is thought to cause blood vessels to narrow, restricting the heart's oxygen supply, lead author Professor David Erlinge, from Lund University, said.

Colds and flu are also more common during the winter months, which have been shown to increase vulnerable people's risk of a heart attack, he added.

 The researchers analysed 16 years of weather and heart attack date between 1998 and 2013. 

This included information on more than 274,000 people aged between 50 and 89. 

'Days with low air temperature and atmospheric pressure, high wind velocity and shorter periods of sunshine were associated with risk of heart attack,' Professor Erlinge said.

'The strongest association appeared to be for air temperature - with a higher risk of heart attack on days when air temperatures were less than 0°C (32°F).

'Consistent results were observed after adjustment for long-term trends in heart attack and day of week.

'After adjustment for air pollutant levels, only air temperature remained significantly associated with risk of heart attack.'

Results further suggest that when temperatures rose from 0°C to 3°C or 4°C, the rate of heart attacks fell.

The link between the deadly condition and the weather was most pronounced in STEMI (ST-Elevation Myocardial Infarction).

This is considered the most deadly type of heart attack and occurs when part of the cardiac muscle dies due to a blocked blood supply.

'This translated into a 9.5 per cent reduction in STEMI for each 3.1°C increase in air temperature,' Professor Erlinge said.

In terms of the cause of the heightened risk, Professor Erlinge said: 'Respiratory tract infections and influenza are known risk factors for heart attacks that have a clear seasonal variation that may contribute to our findings.'

A study released earlier this year showed a sixfold increase in a person's heart-attack risk a week after they battled a lung or throat infection.

Cold weather may also make people less active and increase their cravings for fatty comfort food, triggering poor heart health.

Reduced vitamin D exposure during the short winter days may also be to blame.   

'Although the day-to-day association of weather on incidence of heart attack is complex - with a number of factors possibly interacting and affecting the results - a strong association between air temperature and risk is evident,' Professor Erlinge said.

'Adaptation to cold may blunt this association but whether reducing cold exposure by staying indoors and wearing warm clothes reduces the risk of heart attack remains unknown and has to be prospectively studied.'  

Professor Erlinge added drugs are available that could reverse the narrowing effects of cold weather.

'Beta-blockers and aspirin - among other medications - could blunt the possible associations of external triggers through widening of the blood vessels,' he said.

Although the research was observational and therefore cannot prove cause-and-effect, Professor Erlinge added: 'The results were consistent across a large range of subgroups and health care regions.'

Previous studies have established a link between air temperature and the risk of a heart attack, however, most have been restricted to one area or based on unreliable data, he said. 

'To our knowledge this study not only constitutes the largest of its kind but also the only one investigating a wider spectrum of weather variables to clinical data,' Professor Erlinge added. 

N.H.Kh