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Short term effects of temperature on risk of myocardial infarction in England and Wales: time series regression analysis of the Myocardial Ischaemia National Audit Project (MINAP) registry

BMJ 2010; 341 doi: (Published 10 August 2010) Cite this as: BMJ 2010;341:c3823

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  1. Krishnan Bhaskaran, research degree student1,
  2. Shakoor Hajat, senior lecturer2,
  3. Andy Haines, professor of public health and primary care and director3,
  4. Emily Herrett, research degree student1,
  5. Paul Wilkinson, reader in environmental epidemiology2,
  6. Liam Smeeth, professor of clinical epidemiology1
  1. 1Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London WC1E 7HT
  2. 2Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine
  3. 3London School of Hygiene and Tropical Medicine
  1. Correspondence to: K Bhaskaran krishnan.bhaskaran{at}
  • Accepted 1 June 2010


Objective To examine the short term relation between ambient temperature and risk of myocardial infarction.

Design Daily time series regression analysis.

Setting 15 conurbations in England and Wales.

Participants 84 010 hospital admissions for myocardial infarction recorded in the Myocardial Ischaemia National Audit Project during 2003-6 (median 57 events a day).

Main outcome measures Change in risk of myocardial infarction associated with a 1°C difference in temperature, including effects delayed by up to 28 days.

Results Smoothed graphs revealed a broadly linear relation between temperature and myocardial infarction, which was well characterised by log-linear models without a temperature threshold: each 1°C reduction in daily mean temperature was associated with a 2.0% (95% confidence interval 1.1% to 2.9%) cumulative increase in risk of myocardial infarction over the current and following 28 days, the strongest effects being estimated at intermediate lags of 2-7 and 8-14 days: increase per 1°C reduction 0.6% (95% confidence interval 0.2% to 1.1%) and 0.7% (0.3% to 1.1%), respectively. Heat had no detrimental effect. Adults aged 75-84 and those with previous coronary heart disease seemed more vulnerable to the effects of cold than other age groups (P for interaction 0.001 or less in each case), whereas those taking aspirin were less vulnerable (P for interaction 0.007).

Conclusions Increases in risk of myocardial infarction at colder ambient temperatures may be one driver of cold related increases in overall mortality, but an increased risk of myocardial infarction at higher temperatures was not detected. The risk of myocardial infarction in vulnerable people might be reduced by the provision of targeted advice or other interventions, triggered by forecasts of lower temperature.


  • Contributors: KB, SH, AH, PW, and LS designed the study. KB and EH prepared and cleaned the data. KB did the statistical analysis and wrote the first draft. SH, AH, EH, PW and LS contributed to further drafts. KB and LS are the guarantors.

  • Funding: This study was funded through grants from the British Heart Foundation (FS/04/045) and the Garfield Weston Trust. LS is supported by a Wellcome Trust senior research fellowship in clinical science. SH is funded by a Wellcome Trust research career development fellowship (076583/Z/05/Z). The funders had no role in the design or conduct of this review, or in the preparation, review, or approval of the manuscript. All authors carried out this research independently of the funding bodies.

  • Competing interests: All authors have completed the unified competing interest form at (available on request from the corresponding author) and all authors want to declare: (1) financial support for the submitted work from the British Heart Foundation, the Garfield Weston Trust, and the Wellcome Trust; (2) no financial relationships with commercial entities that might have an interest in the submitted work; (3) no spouses, partners, or children with relationships with commercial entities that might have an interest in the submitted work; and (4) no non-financial interests that may be relevant to the submitted work.

  • Ethical approval: This study was approved by the London School of Hygiene and Tropical Medicine ethics committee.

  • Data sharing: No additional data available.

  • Accepted 1 June 2010

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