Dear Doctors: I'm a side sleeper and normally it's on my right side. I got hurt in a soccer game, and for a couple of nights I had to switch to sleeping on my left side. Right away my heartbeat felt louder and stronger. My wife says it happens to her too and not to worry. What is going on?

Dear Reader: The phenomenon you describe is due to physiology, not pathology. That's a fancy way of saying the changes you noticed are due to how the body is structured, and not because something is wrong. To understand what is happening, why in most cases it is harmless, and what types of symptoms may require a closer look, let's begin with a bit of anatomy.

The heart sits in the center of the chest, behind the sternum. The lower tip, known as the apex, is made up largely of the left ventricle, which does most of the pumping. This part of the heart angles downward in the chest and sits slightly to the left of center. The position of the apex puts the left ventricle, which pumps oxygenated blood to the tissues of the body, close to the chest wall. When you lie on your back or your right side, the apex is not affected. But when you lie on your left side, a few things happen that can contribute to what you described.

One result of the switch in sleeping positions is the effect of gravity, which can cause the apex to move closer to the chest wall. The rib cage, which protects the heart and core organs, is somewhat flexible. The weight of the body against the mattress (gravity again) can cause a bit of compression. These contribute to the apex, and thus the strong pumping action of the left ventricle, sitting close enough to the chest wall that many people feel a perceptible thump. The stillness of the body as we drift into sleep, plus the accompanying quiet, can also amplify the physical sensations of this stronger heartbeat.

In healthy adults, sleeping position hasn’t been found to have an adverse effect on the heart or on the efficiency of its pumping action. However, there is some evidence that sleeping position can affect people living with heart arrhythmias, such as atrial fibrillation, or A-fib. This is when the heart can slip into an irregular and often rapid heart rhythm. This does not mean that sleep position causes the condition.

That said, it is important to know that certain symptoms can indicate a problem. These include persistent chest pain or pressure, particularly when it spreads to the arm, back or jaw, unusual shortness of breath, difficulty breathing, dizziness or fainting, and persistent heart arrhythmias. If these occur, it is very important to seek medical guidance right away. But without these warning signs, a louder or stronger heartbeat when sleeping on the left side is usually just a reminder of anatomy and the effects of gravity.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: My doctor put me on a glucose monitor to track my blood sugar for a few weeks. There were three nights when my husband and I went walking after dinner, and those readings were better. He thinks it’s the walking, but I think it’s that I skipped dessert. Who do you think is right?

Dear Reader: Considering this is a family debate, we are happy to be able to say that you are both correct. The behaviors you and your husband have identified -- exercise vs. food choices -- are quite different. However, they both bolster the body’s insulin response, which in turn helps maintain optimal blood sugar levels. The difference between the two actions lies in the mechanisms involved.

Skipping dessert reflects the well-known link between added sugars in the diet and increased blood glucose levels, which is likely why that explanation makes sense to you. Meanwhile, your husband appears to be drawing on the equally familiar concept that regular exercise plays an important role in blood sugar control. It is also possible he has read about recent research showing that a post-meal walk can have a direct and immediate effect on moderating blood sugar. This occurs through a metabolic process that allows muscles to take up glucose through an alternative pathway that is less reliant on insulin.

In the study, published in 2022, researchers in the U.K. analyzed data from seven existing studies that examined the effects of exercise on blood glucose. They found that taking a walk after eating, even one as short as five minutes, improved blood sugar control. Changes in blood sugar were less extreme and more gradual. That’s important because blood sugar spikes are suspected to play a role in Type 2 diabetes. Even better news: The beneficial effect of a post-meal walk lasted for up to 90 minutes. Interestingly, even standing for a few minutes after eating improved blood sugar numbers. However, for those individuals, the effect was far more modest.

We also want to point out that the continuous glucose monitor, or CGM, that your doctor asked you to use on a short-term basis is also emerging as a useful tool. These devices are easy to apply and last a few weeks. They deliver real-time data about the effects of diet and lifestyle on blood sugar levels. This can be particularly helpful for people whose blood sugar numbers are edging into the danger zone of prediabetes.

One of the challenges when it comes to diabetes is that elevated blood sugar is a so-called silent symptom. You can’t feel it when it’s happening. But with the data collected by a CGM, you can see the difference between how a doughnut or an apple affects glucose metabolism, or, on your husband’s side of the equation, the benefits of a post-meal walk. In your own case, the short-term use of a CGM has validated your decision to skip dessert and may even have helped establish a new habit of a nightly post-meal walk for you and your husband.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: As a former NASA mission planner, I would signal a “no-go” for human colonization of the moon and Mars. The human body's functions cannot tolerate the long-term effects of a low-gravity environment. I assume, from your column about the effects of low gravity, you agree?

Dear Reader: You are referring to a column prompted by a reader's son, who became fascinated by the drama of two U.S. astronauts last spring. Their mission aboard the International Space Station (ISS) encountered technical difficulties, and their eight-day mission stretched into an unplanned nine-month stay. In that column, we explored how prolonged microgravity interferes with biological systems. It affects bone remodeling, fluid balance, circulation, red blood cell metabolism, vestibular systems and even going to the bathroom.

Space tourism -- and the technologies that make it possible -- have had rapid advances recently. So it’s more relevant than ever to study the health effects of space travel on the human body. Your own question happens to coincide with the release of new findings about the potential effects of spending extended time in microgravity. The journal Proceedings of the National Academy of Sciences published the study earlier this year. The study found that, following spaceflight, the brain shifts position in the skull.

In this new study, researchers used health data collected from 26 astronauts. Of those 26, 15 underwent preflight and postflight measurements of their brains. The study used existing preflight and postflight brain measurements for the other 11 astronauts. Brain scans showed that, absent gravity, the brain shifts upward and back in the skull. The researchers also noted that different regions of the brain migrated, independent of each other. These changes to the brain were in mere millimeters, but they still impacted both the motor and sensory regions of the brain.

Not surprisingly, astronauts with the longest stays in microgravity underwent the greatest changes. However, measurable brain movement was seen even in those who spent two weeks on the ISS. These shifts led to what the researchers referred to as “sensory conflicts.” For example, astronauts in space could have brief bouts of motion sickness or spatial disorientation. Back on Earth, balance issues could arise. Continued monitoring showed that the brain orientation of the astronauts in the study slowly returned to normal. For those with the longest stays, recovery could take up to six months.

As for a decision on colonizing the moon or Mars, we are relieved this decision isn't up to us. But experts like yourself appear to agree about several important things. One is that we need more research to understand how the human body responds to the rigors of space. The other is that the technology to keep people healthy so far from Earth is not yet in place. This includes things like artificial gravity and radiation shielding. We would also need autonomous medical care, mental health support and on-demand evacuation procedures. Experts in the field agree that until those gaps are closed, deep space missions, including long-term stays on the moon or Mars, will remain out of reach.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

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