Lifestyle+ — 20

What about steps? They are easily and, for the most part, accurately counted by wristbands, smartwatches, and digital accelerometer trackers. The frequently cited threshold of 10,000 steps per day has never been validated, whereas many studies have demonstrated benefit that starts at much lower levels, depending on the features of the cohort. For example, for a cohort of about 17,000 women with a mean age of seventy-two years, there was an association of reduced all-cause mortality that was seen at 2,700 steps/day, and magnitude of benefit increased to a plateau at approximately 7,500 steps/day. A systematic analysis of twelve studies with over 110,000 individuals found the association of benefit starting at 2,500 steps per day (8 percent reduction of all-cause mortality) and progressive reduction up to 8,800 steps per day (60 percent reduction of all-cause mortality and cardiovascular events). There was additional benefit that noted how many steps were taken per minute, irrespective of the total step count. Coincidentally, the much ballyhooed 10,000-step goal that was advanced without empirical evidence was supported by a UK Biobank study of over 72,000 participants, which found the lowest mortality risk was seen for 9,000 to 10,500 steps per day. The value of walking was noted in an analysis of ten studies, with faster walking speeds, 2.5 to 5 miles/hour, offering more protection from developing type 2 diabetes.

Figure 3.5. The dose-response of exercise training volume and cardiovascular outcomes, with the alternative hypothesis (regarding overly intense physical training) on lower panel. Adapted from Barry Franklin et al., “Exercise-related acute cardiovascular events and potential deleterious adaptations following long-term exercise training: Placing the risks into perspective-an update: A scientific statement from the American Heart Association,” Circulation 141, no. 13 (March 2020): e705–e36, https://doi.org/10.1161/CIR.0000000000000749.

The relationship of exercise and cancer was looked at in nine prospective cohorts with over 750,000 participants, followed for ten years, for fifteen different types of cancer. A significant dose-response curve of benefit—the more exercise, the less cancer—was seen across seven cancer types (colon, breast, kidney, liver, myeloma, non-Hodgkin lymphoma, and endometrial). More recently, when studied in more than 60,000 people for seventeen types of cancer, vigorous exercise was also associated with reduction of head and neck, lung, bladder, and pancreatic cancer.

More than 78,000 UK Biobank participants with wrist accelerometers were followed for seven years to determine the relationship between steps and all-cause dementia: a daily dose up to 9,800 steps was linked to protection, along with steps at high intensity or cadence. The relationship between physical exercise and cognition has been intensively studied, approaching two thousand reports, and eighty randomized trials. A review of the randomized trials suggests that the favorable impact of exercise is consistent but small. The mechanism has been tied to increased brain neurogenesis and plasticity, exercise’s anti-inflammatory effect, and improved cardiovascular health.