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To Dr. Charles Czeisler, the onset of Daylight Saving Time on Sunday morning brings a prospect  more disturbing than simply losing an hour's sleep: It means a measurable increase in car crashes and heart attacks.


Czeisler, a doctor and professor of sleep medicine, and Rebecca Spencer, a professor of psychology, joined the Daily Circuit to talk about the arrival of Daylight Saving Time and the role of sleep — and the lack of it — in health. Highlights from that conversation:


"It makes a huge difference, first of all, because of the sleep we lose that night. We cut the hour out of the nighttime, so suddenly at 2 o'clock in the morning it becomes 3 o'clock in the morning. And secondly, we have to reset our internal biological clock that controls the timing of sleep. It makes it more difficult for us to get the sleep we need, even in the following week. It's interesting: There's a 17 percent increased risk of motor vehicle crashes in the week after this change, and there's also a 5 percent increased risk in myocardial infarctions, or heart attacks." (Czeisler)

On how light sources affect our sleep patterns:


"Especially from a screen, because the screens are enriched. Because they are solid-state lighting, emitted by light-emitting diodes, they are enriched in blue or shorter wavelengths of light, which have the most powerful effect on the 

 probably derived in the earliest organisms in the oceans, where the main source of light was blue light. So we have a separate set of photoreceptors that mediate the resetting of our internal clock, that are different from the rods and cones that mediate conscious vision. So just as in the same way the ear has two functions — one is hearing, the other is balance — the eye has two functions. One is sight, and the other is the resetting of this internal clock, or circadian photoreception." (Czeisler)

The ways a lack of sleep can make us sick:


"New discoveries about the connectivity between disturbed sleep and health are being made all the time. 

, for example, which is probably present in about a quarter of the adult population, is the leading known cause of high blood pressure, or hypertension; 70 percent of patients with diabetes have sleep-disordered breathing, and similarly with congestive heart failure. In fact, 'burning the candle at both ends' ... many people don't realize how hazardous not getting enough sleep is for their health. Simple things like getting a flu shot: You'll only have half the antibody response if you are not getting enough sleep in the week before you get the flu shot. You're at much greater risk for catching the common cold if you're exposed to the 

, 200 to 300 percent increased risk of actually getting sick, and your risk of calcification of the coronary arteries, over a five-year interval, is more than 100 percent increased, if you, again, are burning the candle at both ends and not getting an adequate amount of sleep." (Czeisler)

How daylight saving time risks your health

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