Every tissue and organ in your body operates according to a biological tempo known as circadian rhythm.

Your body clock, which is located in your brain’s hypothalamus, ensures biological processes run according to schedule.

It oversees about a dozen so-called “clock genes” that are expressed differently at various times of the day or night to meet the body’s demands during waking and sleeping hours. Such processes include eating, sleeping, and temperature regulation.

“Chronobiology” is a fast-growing scientific field that focuses on the effect of these circadian rhythms.

Unfortunately, people tend to live out of sync with their body clock by performing too many activities at night. This wasn’t the case for most of human history, because until the invention of electricity, darkness meant danger.

The body clock evolved to take its cues from light. For instance, as light dims at night the body clock increases production of melatonin, the sleep-inducing hormone.

But thanks to electricity, we can now carry on activities well into the night. And because the body clock can’t distinguish natural from artificial light, production of melatonin is suppressed, and natural circadian rhythm is disrupted.

As the saying goes, “timing is everything.” One powerful example of this adage is how circadian rhythm affects your heart.

Research consistently finds that heart attacks, arrhythmias, and even cardiac deaths are likeliest to occur in the early morning hours, between about 4 a.m. and 10 a.m.

At night, blood platelets are at their stickiest, raising the possibility of clotting.

Then prior to waking, the brain initiates the release of the hormone cortisol, raising heart rate and blood pressure — along with the potential for a heart-attack inducing clot rupture. Scientists are also finding that body clock disruptions may raise the risk of coronary artery disease, stroke, high blood pressure, diabetes, cancer, and Alzheimer’s disease.