Daily Step Count and All-Cause Mortality: A Dose-Response Meta-analysis | Hacker News Reader

Daily Step Count and All-Cause Mortality: A Dose-Response Meta-analysis

pubmed.ncbi.nlm.nih.gov

76 pointscaaqil58 comments

As someone who, over the last year, has gone from sedentary, in front of the computer lifestyle, to jogging 5K 3 times a week on the treadmill and getting 10K steps per day half the days in the last month...

My wife and I both feel 20 years younger. The change brought on through a number of lifestyle changes has been dramatic and basically entirely positive.

Yes, steps is only one component of it. But: I could also see that steps probably do correlate with other healthy lifestyle choices. Just making time in the day for a half hour walk or an hour on the treadmill is an indicator of prioritizing some health choices over other things.

Yes, I agree! I've gone from not doing enough exercise to a level where I'm pretty happy too (hope to work up to doing 10K at a decent pace but I can do 5K without too much difficulty now). I'm really enjoying doing swimming (1.5 to 2K a week), jogging not as much at first but it's growing on me as I'm getting fitter!

Having made the effort myself over the last year and a half, it's pretty surprising seeing so many 'correlation is not necessarily causation' people here (yes, we all understand the concept) basically imply that everybody probably does as much exercise as they possibly can for their level of health, so it might all just be a correlation... It seems quite clear from general observation that a huge proportion of the population could exercise much more than they do, but don't. (I definitely didn't!). It also seems surprising because that argument basically seems to dispute the idea that exercise makes you healthier...

There's definitely both correlation and causation happening. But walking and jogging is really good for health, people shouldn't just write it off! Here's a good study on walking interventions and positive health outcomes, for example - https://pubmed.ncbi.nlm.nih.gov/25601182/

Lots of focus on the step count while IMT/IMST breathing muscle training seems much more convincing (for the young and healthy as well as for the frail):

"5-minute breathing exercise lowers blood pressure better than working out, medication" https://news.ycombinator.com/item?id=27747943

"Thanks HN: For Me, Breathing exercise for High Blood Pressure is Working" https://news.ycombinator.com/item?id=27980060

Breathing resistance training might even reduce the need of Covid emergency care and the long Covid symptoms:

"Respiratory Muscle Performance Screening for Infectious Disease Management Following COVID-19: A Highly Pressurized Situation" https://www.amjmed.com/article/S0002-9343(20)30347-8/fulltex...

The IMT study this is based on is tiny compared to the meta-analysis for steps. It also only tested blood pressure and for a short amount of time compared to all-cause mortality over years in the meta-analysis.

It's really hard to report on correlation without implying causality.

So whenever you see research popping up in your news feed just flip the order of statements in the title.

"People at greater risk of dying walk less"

Then read the paper carefully for any signs of something that doesn't fit this flipped version.

"Correlation consists even when controlled for smoking and comorbidities"

It still can be true because smoking is just one factor out of thousands factors contributing to early deaths, and comorbidities probably bunched up so many unrelated stuff together that you could control for some random stuff and get really close results. And even if they accounted for all the comorbidities precisely still people with each might be in different condition and those farther from death might want to walk more.

Agree. But even this meta-study of 175370 person-years only encountered 2310 deaths.

Imagine what it would cost to make an interventional study and track how accurately people report they are walking.

But even the credibility of this is somewhat higher than a pure "correlation" or cross-section study, because the dying is in the future, compared to when the walking is counted ("prospective" cohort studies).

And there is no possible blind study, because the participants know they are walking, and you can't have a "placebo walk".

> no possible blind study,

Not sure I agree with this.

I am definitely not saying this should be done, but as a thought experiment:

Imagine you worked for Fitbit, and could choose to undercount steps slightly.

You have a cohort of users who will walk each day until they reach 10k steps. You undercount steps for a random subset so that they end up walking 10.5k.

You repeat this experiment so you make the folks with a 5k goal actually walk 5.5k, etc

This is a pretty good blinded study. The difference is slight enough that the users don't notice the extra increase in distance consciously.

(Obviously you have to take into account the risk of churning people from the service somehow.)

If you were to check all cause mortality somehow (look up public death records? Some other way?) That would seem like a pretty good study design.

Again, perhaps unethical to do this without consent; but not impossible; you could ask a cohort of users to opt in to this sort of study.

If the claim is that it's distant dependent, this would likely take you a lot closer to causality.

This. Most research I see on factors related to activities vs death rate seem to have a pretty big duh! factor--are they healthy enough to be able to do the activity and consider it worth the effort it will take to do. There's no way they can possibly control for comorbidities because not everything is in the medical records, nor do medical records have all the details of severity or how it limits someone.

Even for things where ability doesn't really enter into it there's also the factor of the level of effort one spends on self-care. If I'm near death am I going to bother with the dentist unless something hurts?

Other possible sources of bias: People who walk more live in more walkable neighborhoods and are likely more wealthy, live in places with less air pollution, have less traffic noise disturbing their sleep, and travel fewer miles in cars thereby reducing risk of car accidents.

And wealth also possibly means access to better nutrition, better healthcare, and lower stress overall.

What if the difference is because of pre-existing health state and conditions of those people i.e. those who's health is poor enough they are likely to die soon, just don't have energy to walk a lot?

Meaning, this may be a classic case of correlation which is not a causation.

I would speculate that in particular case of the U.S., there is also a social factor in play that is, people with different health outcomes and longevity are also people from different social classes who may or may not have time and space/environment appropriate for these activities?

This is addressed in the full text, which you can find on a certain hub.

>The inverse association persisted in the subgroups defined by age, geographical location, follow-up duration and devices used for counting steps, as well as after adjustments were made for important confounders including body mass index, alcohol drinking, smoking status, step intensity, and pre-existing comorbidities

It just addresses some factors not all of them.

It still could be just that healthier and better feeling people are inclined to walk more.

>These findings were supported by the findings of intervention studies wherein increasing steps per day resulted in significant improvement in cardiometabolic risk factors [41, 42].

Is it really that far fetched that those who get more exercise and burn more calories are healthier and live longer?

Speaking for the depraved, I think the obvious questions are how little I _must_ drink, how much I _must_ exercise, etc.

Ideally it would be "uncorrelated" and "none"

Seems unlikely, though

> the obvious questions are [...] how much I _must_ exercise

https://www.who.int/news-room/fact-sheets/detail/physical-ac...

> Adults aged 18–64 years

> should do at least 150–300 minutes of moderate-intensity aerobic physical activity [per week]

> or at least 75–150 minutes of vigorous-intensity aerobic physical activity [per week]

> should also do muscle-strengthening activities at moderate or greater intensity that involve all major muscle groups on 2 or more days a week

> Replacing sedentary time with physical activity of any intensity (including light intensity) provides health benefits

Less obvious but still interesting: At which point does diminishing returns set in? At some point does one extra hour of exercise yield less than one hour of increased average lifespan, and so not worth the additional effort, for someone that doesn't find exercise to be intrinsically rewarding?

Not at all. The only question is whether number of steps is a valid measure of how much exercise you're getting. Higher step count means people are walking more which means more general activity which is good. However, there are other relevant factors to consider such as walking speed, cardiac frequency, the intensity of the exercise. There are also other ways to exercise which don't involve steps at all. Weight lifting for example.

In other words, people who can’t walk or can barely walk are likely not that healthy - is probably a more intuitive theory than walking causes better health.

> a more intuitive theory than walking causes better health.

Why? Genuine question. In todays world, people drive themselves in cars and then park themselves in chair for hours. Then, on other end there are people having physical work that is literally body destroying - or people who literally go too much all in sports.

Why would it be unintuitive that normal walking around, mild exercise related to easy day to day activity would be better for health?

The correlation held for 10,000 to 17,000 as well as 0 to 10,000 steps. Are people doing 10,000 steps/day “barely able to walk”?

Yeah I think there’s a difference in cardio fitness between people who do 10000 and 17000. Less fitness makes the latter more difficult.

Obviously that will be the case to some extent, but it doesn't necessarily explain the whole effect, given this part:

> Dose-response meta-analysis indicated a strong inverse association, wherein the risk decreased linearly from 2700 to 17,000 steps per day.

I expect (especially in the US) that many or even most people who could walk several thousand steps a day, don't. They talk about the 70+ age group separately, but most of it is talking about the general population and says the relationship holds.

Of course, this meshes with what we already know about the clear links to exercise causing better health - not just things like balance, less risk of injury, bone density etc. in older people but for anybody prevention of or improvements to things like non-alcoholic fatty liver disease (combined with diet), improvements for those with metabolic syndrome, etc. which all contribute to a lot of early mortality.

Healthier people might have more reasons and energy to move beyond what's necessary

Both can be true, and likely are.

> It’s entirely possible that people who are healthier simply tend to walk more than people who are less healthy, and daily step counts are therefore merely a proxy for general health, and don’t have an inverse causal relationship with all-cause mortality. However, I don’t think that’s the case – at least not entirely. For example, a 2015 meta-analysis found that group-based walking interventions, all lasting one year or less, led to significant decreases in systolic blood pressure, diastolic blood pressure, resting heart rate, body fat percentage, body mass index, total cholesterol, and depression scores, while increasing VO2max, 6-minute walk distance, and score on the SF-36 physical functioning inventory. Most walking intervention studies don’t use particularly strenuous walking programs either – generally 20-30 minutes of walking per day, which works out to ~2,400-3,600 steps for most people. So, if a bit of walking can beneficially modify ten different risk factors for all-cause mortality in less than a year, I think we can make a pretty strong case that the inverse relationship between step counts and all-cause mortality is more than mere association.

https://www.strongerbyscience.com/research-spotlight-walking...

> those who's health is poor enough they are likely to die soon, just don't have energy to walk a lot?

True, and there's a feedback loop in there as well. Being inactive leads to significant losses in muscle mass which leads to even more inactivity which compounds the problem. Sarcopenia is a serious problem especially in the elderly.

FWIW:

>The HR was 0.87 (95% CI 0.78–0.97, I 2 = 59%, n = 3) in adults older than 70 years, and 0.88 (95% CI 0.82–0.95; I2 = 86%, n = 4) in the general population of adults (p subgroup difference = 0.11).

for a summary and thoughts on matters of sports and health like this i trust greg nuckols on strongerbyscience: https://www.strongerbyscience.com/research-spotlight-walking...

The link between walking and all cause mortality seems less interesting than, say, stress levels. People don’t go for a walk to cheat death, it’s because they’re in need of a breather.

I know lots of people who walk regularly because they know it's good for their general health and wellbeing... It is true though that it can be really enjoyable and help to de-stress too, but that's not the only reasons people do it.

Right, so the link to general health and well-being would be interesting - not all-cause mortality.

General health and well-being is probably highly correlated with average longevity though.

Stress is a pretty high factor mortality risk, so if walking reduces it, it's probably a real win.

There you snuck that word in- 'probably'. Maybe. But that's not what the paper looked at.

"So I don't die early" is a large part of "general health and wellbeing" for the purposes of my comment.

A breather? Most of the time when I'm walking it's with a pack on my back heading into the wilderness.

It is frustrating to link this to a unit as unspecific as "steps". It's like modern day "hands" or something. I would think it would be incredibly difficult to come to any conclusion before decoupling weight, terrain, shoe material, stride, altitude, etc.

In addition, I've seen people get more unhealthy after taking up the dogma of "steps" as they are now tracking their normal-everyday-routine and using it to justify their lack of medium/high-intensity exercise. "Bing! I closed a ring. I can skip the gym today."

Steps doesn't seem to be a bad measurement as it naturally partially controls for height, and is easy to measure. Not to mention the results are there even when they account for "body mass index, alcohol drinking, smoking status, step intensity, and pre-existing comorbidities" and more. Sure, the results will be noisy but you should still expect to see the effect with a large sample size which this has.

Also, I'm somewhat doubtful that it's common for people to do less exercise after starting to count steps and if anything I'd expect a positive correlation between people becoming more active by walking more and picking up other forms of exercise.

Conditions still matter.

Is a step while out shopping (at around 2,500' elevation) comparable to a step while hiking last Saturday (average something like 500' average elevation, 2,000' of climb, but with about 30 pounds of gear--admittedly, probably 25 pounds by the time I was done), or hiking last summer (same gear, but an average elevation approaching 10,000' and 3,500' of climb)??

(And, yes, I think those first numbers are accurate--a decent portion of it was below sea level, it only started climbing after I had crossed the valley.)

>Is a step while out shopping (at around 2,500' elevation) comparable to a step while hiking

No, but the main other measurement you can use - distance - doesn't account for that either. What does account for it is 'step intensity' which they did control for.

To me the real yardstick is what it does to your heart rate, but I'm not aware of any tracker that records heart rate other than during activities.

My Garmin watch does, at least occasionally. I have it synced to the Health app on my phone. I think it does it more often during recorded activities, but there's still a baseline the rest of the time.

Where does height come into play if it was not controlled for

If the study were asking for distance instead of steps, then taller people will naturally go further in fewer steps. But, at least according to these studies, it is the act of stepping that improves health and not traveling distance.

My apologies, I think in phrased that poorly.

The parent comment I replied to stated:

>Steps doesn't seem to be a bad measurement as it naturally partially controls for height

My question is why would height matter at all in this context if it were not controlled for? Is height associated with mortality?

Height is associated with a lot of things including mortality, yes. But more importantly, as mentioned other easy to measure metrics like distance would ignore that it takes different levels of exertion (due to different height and stride length) to cover a given distance while steps accounts for that to a larger extent.

So following this rationale, wouldn't steps naturally be different with different exertion with different heights? Doesn't seem like it really controls for height from my perspective

There is a very good reason for this. When you are in charge of public health policy, you need measures that are easy to implement by anyone, easy to check, don't involve any complexity or specific objects. That is also why in another popular study[0] push-ups were used as a marker instead of much more precise markers such as blood pressure etc.

[0] https://www.health.harvard.edu/staying-healthy/more-push-ups...

I think the idea of counting steps is more aimed at truly sedentary people, or those who aren't going to the gym at all. Based on the hypothesis that some exercise is better than no exercise at all.

When I was doing 15k steps a day, once I had gotten past about 10k, I started just naturally speeding up to try to fit more steps into my lunch break. That at least added some mild cardio, which led me to start tackling stairs. I was working in the Detroit Renaissance centre, which has 4 towers with 39 floors and 1 with 73. Before losing that job I was beating 15k steps and 39 floors every weekday, which definitely helped my overall fitness level!

Very cool, and super good use of your time

The reason the unit is "steps" is there are now popular inexpensive gadgets that count "steps" so it is a unit for which we are accumulating sufficiently large datasets to carry out such studies. Just like the best camera is the one you have with you, the best scientific data is the kind that is obtainable in large datasets.

Yeah, although those gadgets don't produce accurate data for everyone. My wife's insurance offers rewards for being active so I gave her my old Fitbit when I upgraded. Surprise--she has more "steps" than I do. Nope, she does a lot of things with her hands that register as "steps." (She's not cheating, that's simply how she lives.)

Steps seem to be far more specific than, say, distance. And all the data suggests incorporating walking into your daily life is better than sitting around all day and compensating with visits for the gym, so the people you mock are arguably right.

Yeah, I'm not sure that high intensity workouts are the healthiest choice. I think people do them because they are fun, and short term they do make you fit, but a lot of high intensity activities have harmful effects on your body in the long term.

Is there any like evidence of this? Beyond risks that may be associated with injury if not done correctly. My google search shows mostly positive long term effects.

I very much didn't intend to mock them, in fact I care very much about them, I used to be one of them!

Here is showing the efficacy of MVPA in reducing all-cause mortality. It's notably effective, and should be done in combination with a healthy amount of walking: https://pubmed.ncbi.nlm.nih.gov/25844882/

If you only do one or the other you are effectively trying to p-hack your way to health, as these are likely highly associated datasets. Those who live long are likely to be doing both and living a so-called healthy lifestyle.

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