Subtitles section Play video Print subtitles KC is a 79 year old man, presenting to the emergency room with chest pain radiating to his left jaw. His wife Jane, tells the admitting nurse that earlier in the morning, he had become short of breath. He felt nauseous, and light headed, before collapsing to the floor. You see, KC was observing a yearly time change enacted by US Law, Daylight Saving Time, where everyone in the country would set their clock forward 1 hour at 2am the second Sunday in March. Officially, the reason to do this is to save energy and boost the economy by increasing the number of daylight hours during spring and summer seasons, but KC’s case is part of a building body of evidence: this time change can negatively affect human health. Immediately after setting his clock an hour forward, KC felt disoriented. He had done this before for the last 45 years of his life, so there’s nothing different on this Sunday in March. He did have trouble sleeping that weekend because of the time change, though he didn’t think too much of it. But the next day on Monday morning, just before breakfast, KC suddenly felt his jaw become stiff. His chest instantly tightened up. He gripped the armrests of his chair, because every breath he tried to take, was a struggle. He didn’t want to tell his son downstairs, because he thought it would frighten the grandkids. He didn’t want to tell his wife, because he thought she’d overreact. He didn’t think this was a big deal. At lunchtime, KC tried to lay down because he thought he could sleep this off. But 20 minutes later, he vomited 3 times with no relief. KC couldn’t take it anymore. He could barely breathe anymore. His wife found him collapsed on the floor as she called for 911, and he’s brought to the emergency room where we are now. Given this history of present illness, there’s a few clues as to what’s happening. Chest pain with shortness of breath could be a problem of the lungs. But it could also be a problem of the heart. KC had a prior history of diabetes and asthma, which could be the main problem here, but there’s more going on. The medical team immediately draws some of KC’s blood, and they hook him up to an ECG. Proteins and enzymes from his heart muscle were found floating around in his blood, and the ECG confirmed the medical team’s suspicions: KC is having an ST-elevation Myocardial Infarction. Myo meaning muscle. Cardia from Ancient Greek referring to the heart. Infarction from Latin farcire meaning to stuff into, and more modernly meaning a blockage of blood flow, causing cell death. Death of heart muscle, due to a blockage of blood flow. And ST-elevation referring to the ECG reading that he has a specific change in the electricity of his heart, meaning he is having a heart attack, which brings us to the next clue. KC told the medical team that he was a type 2 diabetic. This means that his body’s cells are resistant to insulin. This is a hormone your body releases after you eat. Insulin enables the shift of those nutrients you just ate, in to the cells, like sugar. When the body doesn’t respond to insulin anymore, blood sugars stay high, because they’re not going in to the cells, but also, the body starts putting out wrong signals because it thinks that insulin isn’t being released, so it asks for more. The body, thinks it’s starving and starts metabolizing fat stores in to the blood stream. As these fats float around, some of them, get transported in to the liver, to make cholesterol. All of this causing hyperlipidemia. Hyper meaning high. Lipid referring to fats, And emia meaning presence in blood. High fat presence in blood. This means these blood fats will start pooling in the vessels that supply blood to the heart, called the coronary arteries. The heart is a large muscle. Big muscles are very oxygen hungry, so they need a lot of it to function. Blocking the coronary arteries will starve the heart of oxygen, and cause parts of it to die. And in KC, parts of his heart, were starting to die, bringing us back to the name ST-elevation Myocardial Infarction. KC was at increased risk of heart attack to begin with. At 79 years old, his heart has degraded over time because of normal wear and tear. No one at 80, has the same heart as they did when they were 20. But KC’s heart also degraded more because his diabetes means his body’s metabolism can’t get his blood sugars right. His body can’t get his blood fats right. And his body can’t signal right with the correct hormones. Fats start to pool in his coronary arteries. This causes the smooth muscle lining inside the arteries, to die. But it’s not done h ere. White blood cells rush in to the site because they detect damage. They start to engulf the dead cells of the artery wall, but they also engulf the fats. And as more fats keep accumulating, these white blood cells start to die too [necrotic core]. Smooth muscle cells start to make collagen and proteins, to cover up this dead necrotic core. This fibrous cap seals the area, and the plaque formation is complete. But while this plaque can cause a heart attack by itself ,it isn’t always an ST-elevation heart attack. ST-elevation means full blockage, meaning whatever is there isn’t just fat, but something else too. But what could it be? Well, it would have to be something that’s already in the blood. It could be more fat, but probably not likely since this is so sudden. It’s not sugar because that’s probably not going to clump up in solution. But speaking of clumping up, how about a blood clot? This additional blockage can happen suddenly. It can block the whole thing. It can cause immediate changes in an ECG reading, that changes over minutes, as heart muscle keeps dying from the lack of oxygen. Without fresh blood flowing in, waste products from cells begin to accumulate. The heart tries to compensate, but as each minute passes by, parts of KC’s heart keep dying. But why would this blood clot form? Clots usually form when you get a cut, like on your skin, so did he get a cut inside a coronary artery? How would that even happen? Well, the plaque is made of cholesterols, and white blood cells that died when they engulfed too much fat. The plaque is inflamed. Inflammation is what happens like when you get a cut. Diabetes put someone in a pro-inflammatory state. The immune system expands the blood vessels so more fluid can flow in, and more immune cells can enter the area. The thing is, the chemicals released by the immune cells during inflammation in and around the plaque, breakdown the fibrous cap. The plaque ruptures. Other blood cells think the vessel wall is injured, like a cut, and start clumping there. This completely blocks artery very quickly, causing KC’s sudden heart attack. So that’s the how of KC’s heart attack. But why did it happen? And what does it have to do with Daylight Saving time? Well, it might have a lot to do with it. This brings us to a concept called the circadian rhythm. This refers to our body’s natural clock. Science suggests that human circadian rhythms are based around sunlight. So this directly ties our internal clocks with sleep. This is why it’s harder to take a nap in the morning if you’ve been sleeping well the past few nights. It’s why many people feel gross pulling all-nighters and waking up at night time when it’s dark outside. And the sunlight hypothesis is why we think computer screens, which mimic daylight, keeps us up at night and disrupts sleep. There are differences between people in terms of their biological clock. Some are early morning people. Some are night owls, but the overwhelming majority of people show differences in the activity in their bodies at different times of day. In human experiments, we’ve found that sleep deprivation increases inflammation. The average sleep duration in Western societies decreased from 9.0 to 7.5 hours in the last 100 years, and it looks like it’s decreasing still. In that same experiment, scientists found that depriving someone of sleep, impairs their insulin sensitivity and glucose tolerance. More evidence from decades worth of studies show that night shift workers, that is people who work overnights, do have a higher chance of developing diabetes and cardiovascular disease over years if they keep working those tough shifts, due increased inflammation, decreased insulin sensitivity and impaired glucose tolerance. All three of these, were already a problem in KC because he had diabetes, but there’s more. Daylight saving time has been shown to disrupt human circadian seasonal adjustment. On the second Sunday in March, most of the United States sets their clock forward one hour. This date, sits about a week and a half from the northern hemisphere spring equinox. Right around this time, sunrise and sunset widen dramatically, which means our bodies are already adapting to seasonal change. But when an arbitrary one hour shift happens, it forces yet another change on our bodies. This extra disruption in circadian rhythm significantly changes what genes are expressed in the bodies. It inflicts signal changes disrupting sleep, increasing inflammation, decreasing insulin sensitivity, causing a cascade of metabolic derangements. Some of the data shows that there is an increased incidence of heart attack in the days following the 1 hour forward adjustment, in line with the scientific reason for why it happens. Young people can tolerate these changes, but elderly with preexisting conditions likely cannot handle this, which brings us back to KC. As each minute passes, his chances of dying from his heart attack increase. He’s immediately sent in to the hospital’s Cath lab. This is a place where doctors can use imaging equipment to see the arteries and chambers of his heart. They send a small wire through a blood vessel in his wrist, to reach his heart. They find the blood vessel that’s completely blocked. A balloon is placed on the wire and through the blockage, and it’s inflated, popping the blood vessel open. A mesh called a stent is placed to help keep that artery open.