Health hazards of daylight savings time: ‘springing forward’ to a heart attack.

Did you know that adjusting the clock up by an hour in accordance with daylight savings time increases you chance of a heart attack?

Circadian rhythms are biological cycles that occur in humans, animals, insects, plants, and even bacteria with a period of approximately (circa) one day (diem). These rhythms are determined internally by a part of our hypothalamus and are synchronized perfectly to our 24-hr days by the sun and other cues. This internal clock mediates daily variation in everything from hormone levels, to sleep/wake cycles, feeding bahaviour, thermoregulation, to bowel movements and cardiovascular function, among many others.

It is largely due to these predictable circadian rhythms that risk of a myocardial infarction (heart attack) is significantly highest in the morning (by about 40% as compared to other times in the day). Right as we awake, our cardiovascular system is in the most compromised state –systolic blood pressure and heart rate show the largest upward spike in the morning, blood vessels ability to dilate in response to increased blood flow is compromised (relative endothelial dysfunction), blood clots are more likely to form, and the ability to break them up is at its lowest point in the day. Is it any wonder then, that the first snowfall – shoveled early in the morning by people at risk – always leads to a spike in heart attacks?

Interestingly, the 1hr shift experienced by citizens of many countries (most notably Europe and North America) during the fall and spring in accordance with daylight savings time also has a detrimental effect on cardiovascular risk. The problem lies in the fact that our circadian clock takes time to adjust, and it is best adjusted by changes in day/night or light/dark cycles – not simply the adjustment of our watch. Thus, the few mornings after the clock change our internal clocks are at odds with our watches and particularly in the spring – when one hour of sleep is lost, we wake up with our cardiovascular system being in an even more compromised state than normal.

A 2009 study in the New England Journal of Medicine clearly shows this effect. In the study the authors investigated the number of heart attacks in Sweden the week before and the week after the 1hr clock changes in both the spring and fall. As would be predicted, individuals had an approximately 5% greater risk of having a heart attack immediately after the ‘spring ahead’ clock change compared to the previous week.

The authors rightfully suggest that individuals at risk of cardiovascular complications would be better off changing their clocks more gradually (i.e. by 15 minutes, starting on the Friday before the change). Even more importantly, avoiding strenuous activity and stress right in the morning may also be a valid suggestion.

An even better strategy from a public health standpoint would be to do away with daylight savings time altogether. But what do I know? I’m sleepy and grouchy due to that lost hour of sleep…


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4 Responses to Health hazards of daylight savings time: ‘springing forward’ to a heart attack.

  1. Vicky Knight says:

    The whole process of Daylight Saving Time is outrageous and should be outlawed. We are PEOPLE. We have inner time clocks and body signals. Even roosters know when to crow.

    Does government have the right to overrule our right to simple peace, rest and relaxation for a few gallons of OIL? OIL is the whole purpose behind this and it is insane. There are serious health issues associated with Daylight Saving Time and changing the clock is dangerous, especially to our children. GOOGLE IT.

    Please write your government representative to have this practice stopped.

  2. excellent submit, very informative. I wonder why the other specialists of this sector do not realize this. You should continue your writing. I am sure, you have a great readers’ base already!

  3. nyc says:

    Nice photo.

  4. CH says:

    I agree wholeheartedly. The is NO benefit to it. People who really think they need an “extra” hour of sunlight in the evening should just find a job that starts an hour earlier. Some employers might even let them change their hours without changing jobs.