Tag Archives: life expectancy

Running for life?

In this week’s health news, running will make you live longer.  Maybe.  Maybe not.

The National Post headline announced that  “Running for five to 10 minutes a day may add three years to lifespans, study suggests“(7/29/2014).  I shouldn’t blame the journalists for exaggerating when the journal article title oversells the study findings as well:  Leisure-Time Running Reduces All-Cause and Cardiovascular Mortality Risk.  (Lee D, Pate RR, Lavie CJ, Sui X, Church TS, Blair SN. J Am Coll Cardiol 2014; 64:472-81.)

The study basics:

  • subjects = 55,137 people who visited a health clinic for a check-up between 1974 and 2002; mostly white, middle to upper class, college educated
  • Data was gathered at the first visit and, where possible, at a second visit whenever that might have occurred.
  • National Death Index used to identify death through 2003.
  • Running was self-reported estimate of activity over previous six months including frequency, duration, distance and speed.

 All of the graphs in the paper illustrate differences in hazard ratio (risk of death in one group compared to another group) rather than differences in actual mortality rates.  The paper provides mortality rates adjusted for baseline age, sex, and examination year so I’ve graphed those rates for comparison.

running and mortality bar chart

We can make predictions based on this information.  Each person-year is observing one person for one year.  So 10,000 person-years could be following 10,000 people for one year, 5,000 people for two years, 1,000 people for ten years or some other combination.  Comparing a group of 10,000 non-runners to a group of 10,000 runners, you would expect to observe 15 more deaths in the non-running group (45 vs. 30).

Another way to describe this is using Absolute Risk Reduction for all-cause mortality.  The ARR = 0.146%.  So, yes, runners did have a 30% lower risk of dying from any cause but the risk of dying was low anyway (0.45% in non-runners) so 30% isn’t really much of a difference.

The big problem with the conclusions stated by the researchers is that association does not equal causation.  They found that runners had lower all-cause mortality.  That does not prove that running reduces mortality.  In fact, in another part of the study, non-runners at the first visit who became runners as of a later visit, did not have lower mortality.  This study observed people who chose to run and chose how much they ran.  Higher duration, frequency, and/or intensity of running did not result in lower mortality.

Which leads to the newspaper headline.  Can running five minutes per day add three years to your life?  Probably not.  The study didn’t even attempt to answer that question.  They estimate that the life expectancy of non-runners  is three years shorter than runners.

This study is not proof that, if you start running, you will live longer.

Do you really want to live that long?

After writing the post yesterday “All men must die“, it seemed fortuitous today to read an editorial in The Medical Post entitled “You gotta die of something“.  Dr. Murray Waldman’s essay notes that extensions to life expectancy are limited by human life span.  The oldest human on record died at 122.  We are all going to die.  What will die from if not heart disease or cancer or infection?

The answer is neurodegenerative diseases. This includes Alzheimer’s disease, ALS (Lou Gehrig’s Disease) and similar currently uncommon conditions. All these diseases have two characteristics: They have no effective treatment and their incidence rises extremely sharply after the age of 90.

This should be an alarm bell to those working in the field of life-prolonging technologies. If there is an absolute limit to human life expectancy and that limit appears to be approaching quickly, should we not pause and re-examine what we are trying to achieve?

Living long enough to die of Alzheimer’s or some similar disease is a fate most of us would not wish on ourselves or our loved ones.

I don’t want to live to 120 if the last 30 years are spent suffering from dementia and wearing diapers in a nursing home.  No thank you.

Life expectancy?

Earlier this week, I noticed Tweets from people alarmed about a shockingly low life expectancy of only 37 years for aboriginals in Toronto.  This instantly seemed wrong.  The links lead to an article on the Kevin Newman Live website by a producer, Jordan Chittley.  I found the number cited to be unbelievable and it is.  Colby Cosh caught the error but many others did not.  I sent a series of tweets to the author; the headline and article have since been edited but still contain errors.

The story reports the results of a study “Early deaths among members of Toronto’s aboriginal community” written by three doctors — C.P. Shah, R. Klair, and A. Reeves — from Anishnawbe Health Toronto.  The data used for the study was from just 109 deaths of patients from four clinics in Toronto over three years.

The original article and headline referred to “life expectancy” which is quite different from “average age at death”.  Calculating life expectancy requires knowing the risk of death at each age (or in each age group) in a population.

The authors of the report did not even actually calculate average age at death for aboriginals in Toronto.  They only calculated the average age at death for patients in their clinics who died during those three years.  This doesn’t account for all of the patients who haven’t died yet or all of the aboriginals who are not patients at their clinics.  Their data is useless.  They might be able to make a comparison if they could identify non-Aboriginal patients at similar clinics but even then they are just comparing people who died.  What percent of patients died?  What were the causes of death?  Who is their patient population?  Is it representative of the entire aboriginal population of Toronto?  So many unanswered questions.

The errors in the report are perpetuated by the media including the corrected version of the CTV article.  Almost every article that I’ve seen compares the average age of death of this small group (37 years) to the correctly calculated life expectancy of Toronto residents (75 years).  The two statistics are completely different and should never be compared.  At least Metro News got it right. 

So what are the facts?  Aboriginals do have a lower life expectancy than non-Aboriginals but only by a few years and both groups can expect to live far past 37 years.