medwireNews: Having diabetes exacerbates the adverse effects of extreme temperatures on people’s risk for having an acute myocardial infarction (MI), say researchers.
Indeed, only diabetes patients had an increased MI risk at very high temperatures, report William Bernard Goggins (The Chinese University of Hong Kong) and study co-authors.
“The dual phenomena of global warming and the global epidemic of diabetes may lead to increasing numbers of heat-related [acute] MI events among [diabetes] patients,” they write in PLOS Medicine.
The team analyzed all 53,796 acute MI admissions to public hospitals in Hong Kong between 2002 and 2011, 30.8% of which occurred in patients with diabetes. When the temperature dropped below 12oC, people with and without diabetes had respective 2.10- and 1.43-fold increases in the risk for acute MI admission, relative to when the temperature was 24oC.
“It is important to note that, while we present our findings in terms of absolute temperatures, in general, ambient temperatures relative to the norm for a particular climate have been found to be very important in terms of impact on health outcomes,” says the research team.
For this reason, the temperature thresholds identified in this study cannot be applied to other geographic regions, they stress.
The association between cold temperatures and MI risk was significantly stronger for the diabetes patients, at a relative risk ratio of 1.46 compared with people without diabetes. And the effects of cold temperature lasted for 22 days, so people’s risk remained elevated for that time even if the temperature rose.
The risk difference between patients with and without diabetes was particularly pronounced for those younger than 75 years, leading the researchers to suggest that the presence of diabetes “may remove the protective effect of younger age […] by compromising thermoregulation ability at a relatively younger age.”
Diabetes patients also had a significant 14% increased risk for MI admission when the temperature rose to 30.4oC compared with 28.8oC, which persisted for 4 days, whereas the risk did not significantly increase in people without diabetes. Again, the risk difference between the two groups was most pronounced for people younger than 75 years, at a significantly increased relative risk ratio of 1.33.
The researchers note that the generally smaller associations with high temperatures, relative to low temperatures, may be due to the shorter lag, citing a previous study that found the effect of high temperatures could be best captured by examining hourly, rather than daily, temperature.
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