Melting snowman on the warm rainy day in the middle of January winter weather anomalies.

    Heart attacks more likely after sudden falls in temperature, study finds

    2 March 2018

    Sudden swings in temperature are associated with a significant increase in the number of heart attacks, according to a new study by the University of Michigan.

    It is well known that cold weather brings with it an increased risk of heart attacks, but most previous studies have focused on overall daily temperatures. This new study is among the first to examine associations with sudden changes in temperature.

    The research is based on data from more than 30,000 patients treated at 45 Michigan hospitals between 2010 and 2016, all of whom had been diagnosed with ST-elevated myocardial infarction, the most serious form of heart attack.

    The researchers calculated the temperature fluctuation preceding each heart attack based on weather records for the hospital’s ZIP code. Daily temperature fluctuation was defined as the difference between the highest and lowest temperature recorded on the day of the heart attack.

    Overall, the results showed the risk of a heart attack increased by about 5 per cent for every five-degree jump in temperature differential, in degrees Celsius. Swings of more than 25 degrees Celsius were associated with a greater increase in heart attack rates compared to a smaller increase with temperature swings of 10 to 25 degrees Celsius.

    The effect was more pronounced on days with a higher average temperature; in other words, a sudden temperature swing seemed to have a greater impact on warmer days.

    Hedvig Andersson, the study’s lead author, said: ‘Global warming is expected to cause extreme weather events, which may, in turn, result in large day-to-day fluctuations in temperature. Our study suggests that such fluctuations in outdoor temperature could potentially lead to an increased number of heart attacks and affect global cardiac health in the future.’

    ‘While the body has effective systems for responding to changes in temperature, it might be that more rapid and extreme fluctuations create more stress on those systems, which could contribute to health problems,’ he said.