Can exercise ‘undo’ sedentary harms? AP story makes observational data sound definitive

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The story provides no numbers. It doesn’t tell us how much risk of death is increased by sitting 8 hours a day, or how much it is reduced by exercise. It tells us that “Not exercising and sitting all day is as dangerous as being obese or smoking,” but how dangerous is that?

Does the story seem to grasp the quality of the evidence?

Not Satisfactory

The story inappropriately uses cause-and-effect language in the headline and elsewhere that overstates what this study can tell us (e.g. “To reverse damage of sitting, take a brisk, hour-long walk”). It should have said that walking, sitting, etc. are “associated with” or “linked to” health effects, but not that walking can “undo” or “reverse” damage.

In the study itself, the researchers provide a long list of limitations that suggest a lack of certainty regarding the strength of these conclusions. But the story did not report on any of them. For example, the researchers state,”we attempted to minimise bias from reverse causation (ie, illness causing individuals to become sedentary) by including apparently healthy participants; however, we cannot fully rule this bias out.”  What this means is that the results could be skewed by individuals who had undiagnosed, subclinical disease that caused them to become less likely to exercise. While the assumption is that lack of exercise makes people sick, perhaps the reverse is true in some cases, which would obviously affect results from a study such as this one.

Does the story establish the true novelty of the approach?

Not Satisfactory

Although the story nods to previous research, noting that “Previous studies have found that prolonged sitting can raise the chances of heart disease, various cancers and an earlier death,” it doesn’t explain that this study is meant to address a specific issue that has generated conflicting results in previous research. Here’s how the researchers put it:

Two other meta-analyses had examined the associations of sitting time with non-communicable disease incidence and mortality. One of these concluded that prolonged sitting time was associated with increased risks of deleterious health outcomes regardless of physical activity level, whereas the other concluded that physical activity (no details on the amount of activity were provided) seemed to attenuate the increased risk of all-cause mortality due to high sitting.

In other words, this newer study was attempting to answer this question: Given the conflicting results from older research, what role does physical activity play, if any, in counteracting prolonged daily sitting?