The Harvard strength-training study's hidden longevity lessons

Including: the one exercise type that beats weight training; the cancer J-curve; reverse causation issues with brain-related diseases & resistance training; and a potentially big data pothole.

When the British Journal of Sports Medicine published a paper¹ a few weeks ago showing a long-term correlation in older adults between strength training and living longer, many media dutifully reported the intriguing main finding: just 90 to 120 minutes per week of resistance exercise was linked to:

• a 13% lower risk of all-cause mortality (ie, risk of dying from any cause)

• a 19% lower risk of cardiovascular mortality (dying from heart-related causes)

• a 27% lower risk of neurological disease mortality (dying from dementia, etc.)

Mortality risk means the chance of dying; the bigger the percentage decrease in that risk, the greater the impact on longevity. As obvious or intuitive as it might seem to some people, moving your body against weighted resistance, this study suggests, could play a significant role in helping you live longer.

But it doesn’t compare to cardiorespiratory training, and that’s one giant takeaway that nearly all the media posts on this longevity paper didn’t mention:

Cardio alone was associated with a 26% to 43% lower risk of death, compared with people who did neither cardio nor strength training.

That equates to a roughly 2x to 3x larger reduction in mortality risk than strength training alone. The study authors themselves acknowledged cardio as superior, stating on p. 881 of the journal: “[W]hile either sufficient aerobic or resistance training alone reduced mortality risk, aerobic activity conferred greater benefit”² (italics mine).

Though not a novel declaration, it’s an important reminder that in the constellations of physical movements that may well help you live the longest, combining strength and cardio training creates greater benefits than either one does by itself. If you had to pick the exercise category with the single biggest longevity upside, aerobic fitness—affectionately abbreviated in our culture as VO2 max—is king of the exercise hill.

The paper also concluded that respondents who regularly did strength and aerobic training had up to 45% lower mortality risk than people who did little-to-no exercise.

The big takeaway: “For people who are less active, the key message is that small amounts can still matter,” said Edward Giovannucci, a professor of nutrition and epidemiology at Harvard’s T.H. Chan School of Public Health and one of the study’s authors, in Harvard’s press release about the study. Also: “Building a routine gradually may be more important than trying to do a lot at once.”

But let’s look beyond only the headlines, at what this study also revealed, which you won’t find anywhere else—partly because most media reports on these results were cursory and/or misleading, and because the full paper hasn’t been publicly released.

Other notable features from this Harvard longevity analysis

AGING with STRENGTH obtained a copy of the full text of the paper from one of the Harvard-affiliated authors, on which the reporting below is based.

Other less obvious findings from the full-text of the paper include:

1. a counterintuitive ratio of exercise minutes per week to increased cancer risk

2. strength training’s association with reductions in neurodegenerative (ie brain) diseases may be overstated in the data, due to reverse causation

3. doing more minutes per week of strength + cardio training was linked to reduced longevity gains compared to more modest levels of training

4. a structural weakness in the resistance-training data reporting that arguably calls into question how accurate this paper’s analytical model is

I examine each of these in greater detail below. (If you’re interested in how this research was conducted, please read this footnoted explanation.³)