Cold Weather Coronary Episodes

snowblowerThe way the body responds to low temperatures involves more than comfort. Cold temperatures cause arteries to tighten, restricting blood flow and reducing the oxygen supply to the heart, all of which can set the stage for a cardiac event. The heart has to work harder in the cold weather to keep the body warm, especially in the morning when blood pressure is on the upswing. The “blood pressure surge” just before waking is higher in the winter than at other times of the year. The tight management of blood pressure and cardiovascular health requires careful attention, but more so when the thermometer drops.

Since global climate change has been realized, more because of Earth’s orbital fluctuations than man’s dominion over its resources, interest has grown in the relationship between weather and health.  Measures of mortality have seen a decline when temperatures increase from the coldest days up to a certain point, above which mortality increases with temperature.  Detrimental effects of both hot and cold days also have been associated with cardiovascular mortality.  But it appears that winter has the most impact on circadian rhythm and disturbances in homeostasis that may lead to coronary episodes.

At London’s School of Hygiene and Tropical Medicine, researcher Krishnan Bhaskaran and his team found, “…a broadly linear relation between temperature and myocardial infarction…” whereby “…each 1° C reduction in daily mean temperature was associated with a 2.0% 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..” (Bhaskaran.  2010)

Do bad things happen only to other people?  Most of us are guilty of the “it-can’t-happen-to-me” syndrome.  But could we be right?  This study mentions that, “the risk of infarction in vulnerable people might be reduced by the provision of targeted advice and other interventions, triggered by forecasts of lower temperatures.”  (Ibid.) The operative term here is vulnerable people.”  That deserves a sigh of relief, but not until you determine if you are in or out of that group.  However, the study points out that the adverse effect of the cold temperatures may linger for as long as two weeks.  Keep that in mind.  If you smoke, you’re vulnerable.  Got high blood pressure?  You’re vulnerable.  Lousy diet and nix on the exercise bit?  Yep, vulnerable.  How about being a type A personality with a high-stress lifestyle, or skipping a few visits with the dentist, or being large enough to have your own zip code?  Yup.  You’re in.  Now that you know, what’re you gonna do about it?

Mastering your Self can change the odds much in your favor.  It’s true that additional studies need to be conducted to ascertain the measures that could be taken to reduce risk for cold-weather coronary episodes, but there’s no reason not to start making changes right away.

Meteorological factors that include heavy snowfalls were examined in Scandinavia to look for any implications in cardiac events.  It was found that myocardial infarction (MI) increased especially in people older than 65, but not necessarily in younger groups, when the temperature dropped and the snowfall was heavy.  However, prudent behaviors, such as dressing for the conditions and delaying snow removal until the afternoon, could excuse a considerable number of people from cardiac episodes.  (Hopstock.  2011).  Similar work done by the Mayo Clinic has documented low-temperature peaks in coronary heart disease, suggesting that temperatures below 0° C are associated with sudden cardiac deaths. (Gerber. 2006).

Hypertension prevalence increases in the cold weather and in cold regions of the world, and that can trigger an event.  Animals exposed to these conditions exhibit cardiac hypertrophy (enlargement of the heart) and overactivity of the sympathetic nervous system, which is activated in stressful states and elevates heart rate and narrows blood vessels, thereby spiking blood pressure and setting the stage for an unwelcome happening.  (Sun. 2010).  The proteins designed to constrict blood vessels are especially sensitive to frigid temperatures.  (Chen. 2006).  Strangely, winter temperatures in Sicily hover near 60° F, yet researchers there have found seasonal peaks in infarction-related hospital admissions.  (Sicily’s latitude is very close to that of Washington, DC.) Humidity was included there as a partner in crime.  (Abrignani. 2009)  You’d expect cold weather to be a causative factor in Switzerland, and you won’t be surprised to learn that heavy winds are also implicated, while snowfall and rainfall have shown inconsistent effects.  (Goerre. 2007).

Morning blood pressure is typically higher than later in the day, so taking your medication in the evening may be suggested.  Dressing for the weather is just as important, and warming the air you breathe through a scarf might be a good idea.  Eliminating tobacco and being careful about alcohol intake can keep blood pressure lower.  Waiting for the sun to get higher in the sky, and for the temperature to rise above early-morning freeze, may alleviate cardiovascular stress.

If latitude is considered, it seems that any place outside the tropics is fingered as a winter time hazard for cardiac health.  The body’s ability to manufacture vitamin D from exposure to the sun is compromised at that time of year.  Since certain conditions are prevalent in the winter, when the angle of the sun is low, maybe vitamin D has something to do with it.  Hmm.

References

Krishnan Bhaskaran, Shakoor Hajat, Andy Haines, Emily Herrett, Paul Wilkinson, Liam Smeeth
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:c3823

Hopstock LA, Fors AS, Bønaa KH, Mannsverk J, Njølstad I, Wilsgaard T.
The effect of daily weather conditions on myocardial infarction incidence in a subarctic population: the Tromso Study 1974-2004.
J Epidemiol Community Health. 2011 Jun 6.

Gerber Y, Jacobsen SJ, Killian JM, Weston SA, Roger VL.
Seasonality and daily weather conditions in relation to myocardial infarction and sudden cardiac death in Olmsted County, Minnesota, 1979 to 2002.
J Am Coll Cardiol. 2006 Jul 18;48(2):287-92. Epub 2006 Jun 22.

Sun Z.
Cardiovascular responses to cold exposure.
Front Biosci (Elite Ed). 2010 Jan 1;2:495-503.

Chen GF, Sun Z.
Effects of chronic cold exposure on the endothelin system.
J Appl Physiol. 2006 May;100(5):1719-26.

Abrignani MG, Corrao S, Biondo GB, Renda N, Braschi A, Novo G, Di Girolamo A, Braschi GB, Novo S.
Influence of climatic variables on acute myocardial infarction hospital admissions.
Int J Cardiol. 2009 Oct 2;137(2):123-9.

Goerre S, Egli C, Gerber S, Defila C, Minder C, Richner H, Meier B.
Impact of weather and climate on the incidence of acute coronary syndromes.
Int J Cardiol. 2007 May 16;118(1):36-40.

Bhaskaran K, Hajat S, Haines A, Herrett E, Wilkinson P, Smeeth L.
Effects of ambient temperature on the incidence of myocardial infarction.
Heart. 2009 Nov;95(21):1760-9.

Mercer JB.
Cold–an underrated risk factor for health.
Environ Res. 2003 May;92(1):8-13.

Murakami S, Otsuka K, Kono T, Soyama A, Umeda T, Yamamoto N, Morita H, Yamanaka G, Kitaura Y.
Impact of outdoor temperature on prewaking morning surge and nocturnal decline in blood pressure in a Japanese population.
Hypertens Res. 2011 Jan;34(1):70-3.

*These statements have not been evaluated by the FDA.
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