At least 10,000 steps a day is a goal widely promoted to U.S. adults. Yet, data supporting this goal are limited, with prospective mortality studies offering incomplete evidence. Researchers used data from the National Health and Nutrition Examination Survey, a representative sample of noninstitutionalized U.S. adults, to study the dose-response relationships between step count (steps per day) and step intensity (steps per minute) and mortality.

Valid data were available for 4,840 participants who were age 40 or older and wore an accelerometer for a mean of 5.7 days and 14.4 hours per day. The mean number of steps was 9,124 per day. During a mean 10.1 years of follow-up, 1,165 participants died.

The unadjusted incidence density rate for all-cause mortality was 76.7 per 1,000 person-years for participants who took fewer than 4,000 steps per day, 21.4 per 1,000 person-years for those who took 4,000 to 7,999 steps per day, 6.9 per 1,000 person-years for those who took 8,000 to 11,999 steps per day, and 4.8 per 1,000 person-years for those who took at least 12,000 steps per day. All-cause mortality rates were significantly lower among participants who took either 8,000 or 12,000 steps per day compared with those who took 4,000 steps per day. Higher step intensity wasn't significantly associated with mortality after the researchers adjusted for total steps per day. A higher number of steps per day-but not step intensity-was associated with lower cardiovascular and cancer mortality.

The authors didn't control for all potential confounders, and the steps measured by the accelerometer may include activities other than walking. Wearable activity monitors combined with proven behavioral strategies, they say, may be an effective way to increase physical activity.