Q: In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.
According to researchers, lower temperatures act as an external trigger for the life threatening condition. 
  
 Researchers at Lund University in Sweden found that there was a higher occurrence of heart attacks in sub-zero temperatures. 
  
 London: Heart attacks are more prevalent in the winter season, as lower temperatures act as an external trigger for the life threatening condition, a study claims. 
  
 Researchers at Lund University in Sweden found that there was a higher occurrence of heart attacks in sub-zero temperatures. 
  
 When the daily temperature was less than zero degree Celsius, the average rate of heart attacks a day peaked to four, as compared to when it was above 10 degrees, researchers said. 
  
 Furthermore, occurrence of heart attacks was increased with higher wind velocities, limited sunshine duration and higher air humidity. 
  
 The findings were the same across a large range of patient subgroups, and at national as well as regional levels, suggesting that air temperature is a trigger for heart attack. 
  
 The body responds to cold by constricting superficial blood vessels, which decreases thermal conduction in the skin and subsequently increases arterial blood pressure, researchers said. 
  
 Other responses are shivering and increased heart rate, which raise the metabolic rate and in turn increase body temperature, they added. 
  
 "There is seasonal variation in the occurrence of heart attack, with incidence declining in summer and peaking in winter," Moman A Mohammad from the Department of Cardiology at Lund University. 
  
 "Our results consistently showed a higher occurrence of heart attacks in sub-zero temperatures. The findings were the same across a large range of patient subgroups, and at national as well as regional levels, suggesting that air temperature is a trigger for heart attack," Mohammed added. 
  
 Researchers studied the specific weather conditions during which heart attacks occurred using local meteorological data from hundreds of weather stations. 
  
 During the study period, a total of 280,873 heart attacks occurred of which meteorological data were available for 99 per cent. 
  
 The average number of heart attacks per day was significantly higher during colder temperatures as compared to warmer. 
  
 The results were consistent across health care regions. ||||| Barcelona, Spain - 28 Aug 2017: A 16 year study in more than 280 000 patients has suggested that air temperature is an external trigger for heart attack. The findings are presented today at ESC Congress.1 
  
 "There is seasonal variation in the occurrence of heart attack, with incidence declining in summer and peaking in winter," said first author Dr Moman A. Mohammad, from the Department of Cardiology at Lund University, Skane University Hospital, Lund, Sweden. "It is unclear whether this is due to colder temperatures or behavioural changes." 
  
 This nationwide, 16 year, observational study led by Prof David Erlinge from Lund University, is the largest to investigate the association between heart attack incidence and weather conditions such as air temperature, sunshine duration, precipitation, and air pressure. 
  
 Using the Swedish myocardial infarction registry (SWEDEHEART), all consecutive heart attacks treated at a coronary care unit between 1 January 1998 and 31 December 2013 were included in the study. The investigators studied the specific weather conditions during which heart attacks occurred using local meteorological data from hundreds of weather stations in the Swedish Meteorological and Hydrological Institute (SMHI). 
  
 The average daily minimum temperature was calculated for the entire country as well as the six healthcare regions in Sweden and stratified as <0 °C, 1-10 °C and >10 °C. The relationship between the average number of heart attacks per day and the average minimum air temperature was evaluated. 
  
 During the study period, a total of 280 873 heart attacks occurred of which meteorological data were available for 99%. The average number of heart attacks per day was significantly higher during colder temperatures as compared to warmer. The results were consistent across healthcare regions. 
  
 On a day-to-day basis, this translated into four more heart attacks in Sweden when the average daily temperature was less than 0 °C as compared to when it was above 10°C. Furthermore, the occurrence of heart attacks was increased with higher wind velocities, limited sunshine duration and higher air humidity. Consistent results were observed in ST-segment elevation myocardial infarction and non-ST-segment elevation myocardial infarction. 
  
 The investigators analysed the relationship between heart attack incidence and weather conditions in subgroups including the elderly, those with hypertension, diabetes mellitus or previous heart attacks, and patients taking various medications. The link between heart attack incidence and weather conditions was stable across subgroups. 
  
 Dr Mohammad said: "Our results consistently showed a higher occurrence of heart attacks in sub-zero temperatures. The findings were the same across a large range of patient subgroups, and at national as well as regional levels, suggesting that air temperature is a trigger for heart attack." 
  
 The body responds to cold by constricting superficial blood vessels, which decreases thermal conduction in the skin and subsequently increases arterial blood pressure. Other responses are shivering and increased heart rate, which raise the metabolic rate and in turn increase body temperature. 
  
 "In the majority of healthy people these mechanisms are well tolerated," said Dr Mohammad. "But in people with atherosclerotic plaques in their coronary arteries they may trigger a heart attack." 
  
 As this was an observational study, Dr Mohammad said there were other factors that may have contributed to the results. He said: "Respiratory tract infections and influenza are known risk factors for heart attack that have a clear seasonal variation. In addition, seasonal-dependent behaviours such as reduced physical activity and dietary changes could play a role in the increased occurrence of heart attack during colder weather." 
  
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A:
When the temperature drops, the number of heart attacks goes up, according to a massive 16-year study of some 280,000 patients in Sweden. "There is seasonal variation in the occurrence of heart attack, with incidence declining in summer and peaking in winter," says the lead author in a press release, though it's "unclear whether this is due to colder temperatures or behavioral changes." The team out of Lund University announced its findings at the European Society of Cardiology Congress in Barcelona this week. Using the Swedish myocardial infarction registry (SWEDEHEART), they were able to track every heart attack treated across Sweden between 1998 and 2013. They found significantly more heart attacks in sub-zero temps and fewer in summer months, per Asian Age—to the tune of about four more incidents per day when it's below freezing than when it's above 50 degrees. There could be various factors at play: Our bodies have ways of coping with extreme cold, such as shivering and elevated heart rates, which help raise body temperature but also increase blood pressure. That's no problem for most healthy people, but researchers think that signals trouble for those with plaques in their coronary arteries. Other potential factors tied to the seasons are decreased physical activity, dietary changes, and increased cases of respiratory tract infections and flu. HuffPost reports that extreme cold is one of several "forgotten" risk factors of heart attacks, with large meals and sudden exertion (think snow shoveling) topping the list. (Watch out for high doses of this over-the-counter drug, too.)