Alberta Cancer Foundation

Can you limit your sitting and sleeping to just 23-1/2 hours?


Illustration by Liisa Sorsa

I’m Dr. Mike Evans and I have a big interest in preventative medicine. This could mean a lot of things from cancer screening, to eating more fiber, to having a good social network (and I mean that in the old sense of the word), weighing less, drinking less, smoking less, controlling your blood pressure, cholesterol and so on.

All these are incredibly important and I wouldn’t want you to minimize your efforts in any category.

But what health intervention comes first? What has the biggest impact and return on investment? What one thing can you do that will make the biggest difference to your health? I did my research and I found an answer. I picked out this one intervention because of its breadth.

This intervention, in patients with knee arthritis who received one hour of treatment three times a week, reduced their rates of pain and disability by 47 per cent. In older patients, it reduced progression to dementia by around 50 per cent. For patients at high risk of diabetes and coupled with other lifestyle interventions it reduced progression to frank diabetes by 58 per cent. Post-menopausal women who had four hours a week of the treatment had a 41-per-cent reduction in the risk of hip fracture. It reduced anxiety by 48 per cent and – in a meta-analysis in patients suffering from depression – 30 per cent were relieved with low dose of this intervention that jumps to 47 per cent as we increase the dose. Following more than 10,000 Harvard alumni for over 12 years, those that had the intervention had a 23 per cent lower risk of death than those who didn’t get the treatment.

It’s the number one treatment for fatigue and, my favourite outcome, it improves quality of life. It’s about making your life better – and this treatment has been shown over and over again to improve quality of life. So the question is, what’s this intervention – what’s the medicine – and what is 23 1/2 hours?

The medicine was exercise, mostly walking.

There are 24 hours in a day. You might spend most of your day couch surfing, sitting at work and sleeping. The evidence that I’m going to show indicates that the best thing you can do for your health is to spend half an hour being active, maybe an hour, but if you can do that you will realize all the benefits I described above. Let’s just take a quick walk through some of the medical literature.

Steven Blair, a professor at the Arnold School of Public Health at the University of South Carolina, created the Aerobic Centre Longitudinal study that followed more than 50,000 men and women over time. He looked at something called attributable fractions, the estimated number of deaths in a population that would have been avoided if the risk factor had been erased. An example of an attributable fraction is turning a smoker into a non-smoker. Blair looked at a number of risk factors, but the one that applied the most risk was low cardio-respiratory fitness (CRF). It means really low fitness and it was the strongest predictor of death. Most of the trials that we see are funded by pharmaceutical companies testing a drug for, say, hypertension or high cholesterol or diabetes. We rarely see fitness thrown into the mix.


Illustration by Liisa Sorsa

Blair’s work is interesting; he also undertook another trial looking at obesity. He found two things. First, obesity plus no exercise is a very bad combination. That’s where we see many of the negative consequences of obesity, from a health point of view. But, second, he found that if obese people were active – even if they didn’t lose the weight – their health was much better. The exercise ameliorated many of the negative consequences of obesity.

So, if exercise is the medicine, what is the dose – how long, how often and how intense? I’m going to give you a slightly mixed message: the rate of return seems to decline after 20 or 30 minutes a day but, essentially, more activity is better.

If you are being active less than 150 minutes a week (kids need an hour a day) my flag goes up in the clinic. The literature draws a broad stroke and we see big differences when someone goes from not doing anything to doing something. After that, the return is more granular. The Nurses’ Health Study shows that women who went from zero activity to just one hour a week reduced their heart disease rate by almost half.

And you still see the health gains even if you break it down to three, 10-minute increments to achieve your 30 minutes. But the clinical pearl lies in thinking about your style and habits and your personal cues. Some might only exercise if it’s pre-booked with friends. Or some couples might take a half-hour walk every evening to organize their lives. A dog is a great walking coach; the data show 67 per cent of dog walkers achieved 150 minutes of exercise a week just with the dog walking. And your commute is a great opportunity to work in exercise – getting off a stop or two early or taking the stairs.

I can walk you through some quick slices of the literature.

The first exhibit comes from Japan. In the 1990s, Japan required all employers to conduct annual health screens for employees, and that included a large gas company. They asked: if people’s walk to work was longer, did that reduce their chance of serious health problems, for example high blood pressure? At the Japanese gas company, they found that an under-10-minute walk made no difference to blood pressure. An 11-to-20-minute walk reduced high blood pressure or hypertension by 12 per cent. For walks of more than 21 minutes, high blood pressure rates dropped by 29 per cent. The authors of that study calculated that for every increase of 10 minutes to your daily walk to work, there was a 12 per cent reduction in your likelihood of getting high blood pressure.

The second exhibit is from Germany and it involves stents, which are pretty common in medicine. If an artery starts to get blocked, a vascular surgeon puts in a balloon to open it up and inserts a stent to keep it open. A German researcher named Rainer Hambrecht looked at this with about 100 cardiac patients. He got half the group to exercise 20 minutes day on an exercise bicycle, plus once a week for 60 minutes in an aerobics class. And the other half got the high-tech stent and kept with their normal activity. After one year, 88 per cent of the exercisers were cardiac-event free, compared to 70 per cent of the people who got a stent. So both worked, but I find it amazing that the low-tech intervention, exercise, made a bigger difference. And a stent just fixes just that one part of the heart.

The third exhibit is from Australia and it’s about what I call “sitting disease.” We know that being sedentary is bad for your health. A researcher named Lennert Veerman wanted to quantify it with a big study. He found that, compared to people who watched no TV, those who spend a lifetime average of six hours a day watching TV can expect to live about five years less, and the average adult in the United States watches for about five hours a day. TV is as powerful as many other risk factors for chronic disease.

I’m going to leave you with two quotes. One is Jerry Garcia, the lead singer for the Grateful Dead. And he said, “Somebody has to do something, it is just incredibly pathetic that it has to be us.” And I think that’s true: it has to be us. And Hippocrates said “Walking is a man’s best medicine.”

I’m going to finish by asking you a question. This may have some personal challenges for you; you might be very busy at work, or with kids, or you may be in pain, or you may have other priorities. But my question is this: “Can you limit your sitting and sleeping to just 23 1/2 hours a day?”

Get Going!

Dr. Mike Evans video, 23 1/2 Hours, went viral after its release earlier this year. Watch it here: www.youtube.com/watch?v=aUaInS6HIGo

Dr. Mike Evans is founder of the Health Design Lab at the Li Ka Shing Knowledge Institute, an Associate Professor of Family Medicine and Public Health at the University of Toronto, and a staff physician at St. Michael’s Hospital.