Often while reading health news, I feel like a science referee; there are always competing studies out there, ready for a brawl. Writing for this blog, I sometimes try to take on the umpire’s job of blowing the whistle and sending the competitors into neutral corners while I replay the evidence to see what call to make.
This week in the New York Times’ Well blog, you can get ringside seats for another round of the “how much activity will make me live longest?” smackdown match.
They found that for each 30 minute a day increase in moderate-to-vigorous physical activity, there was a 39 percent decrease in all-cause mortality. But they also found that 30 minutes of even very light activity — doing light household chores, walking slowly over short distances — was tied to a 12 percent reduction in mortality.
“The results apply to all women, all races, regardless of weight and even for women over 80,” said the senior author, Andrea Z. LaCroix, a professor of epidemiology at the University of California, San Diego. “You do not have to be a marathon runner to benefit from physical activity. We hope that physical activity guidelines will recognize light activity as an evidence-based way to lower the risk for death.”
In the other corner, though, standing twitchily, is a rival study (cited in the comments). Here’s what the commenter said:
Interestingly, this study’s conclusions were somewhat the EXACT OPPOSITE of those of a similar, larger study also published this month: “Accelerometer-Measured Physical Activity and Sedentary Behavior in Relation to All-Cause Mortality: The Women’s Health Study,” in the journal Circulation, PMID 29109088.
In that study they similarly found a “strong inverse association between MVPA [Moderate-and-Vigorous physical-activity] and mortality. [But they] did NOT find any associations of Light physical activity or Sedentary behavior with mortality—after accounting for MVPA.”
Hmmm. This definitely merits stopping the clock and re-examining the evidence and claims. One study says light activity confers lower mortality risk for women, and the other study says it doesn’t. So who’s right?
It depends on how you ask.
One of my favorite health researchers, Dutch social scientist Annemarie Mol, writes in a medical ethics article about differing treatments for patients with intermittent claudication, which is muscle pain in the lower legs that is a symptom of a particular type of heart disease in older people. The two treatments she looks at are 1) surgically inserting a stent in the lower legs to increase circulation; and 2) personalized physical therapy to increase the patient’s ability to walk without pain. What she saw was surprising: patients who got 1) improved, and the metrics used to measure their improvement verified this. Patients who got 2), though, did not experience any improvement in the normal metrics, but they DID feel better in many ways: they reported being less depressed, they ate better, slept better, and were steadily improving their walking abilities. One patient reported being very happy that he could walk the two blocks to the local shop to buy his daily cigar.
Which approach is right? Both groups display evidence of improvement, but one group doesn’t have the numbers on their side. However, that group has much improved function and increased quality of life. So maybe both groups are doing well.
How does this relate to the activity studies? The question is: does doing light activity help me live longer? Well, it’s not clear from these studies. What we do know, though, from about a million other studies and interviews and stories, is that activity improves mood, reduces depression, preserved mobility, and helps us feel more in charge of ourselves and our lives. Even if one of our daily goals is a trip to the store to buy a cigar.
We don’t engage in activity in order to maximize our allotment of living. We do it to feel good, to feel good about ourselves, to do what we need and want to do, to feel a sense of accomplishment, to stretch ourselves, and to connect with others.
Is light activity worth doing? Yes. Is moderate to vigorous activity better? Maybe. Sometimes. For some people. If they can, want to, need to. Depends on how you ask.