1. In this large, prospective cohort study limited to women, increasing daily step count was linked with decreased mortality.
2. The above effect plateaued at 7500 steps daily.
Evidence Rating Level: 2 (Good)
Study Rundown: Mobile devices have made step counting easier, and popular media has widely publicized the purported virtues of ‘10,000 steps per day’. This number does not have a clear correlate in the existing literature as a goal for improved health or mortality. In this large, prospective cohort study of older women (mean age 72) in the United States, higher step counts per day was linked with lower rates of mortality with a plateau effect at 7500 steps per day. Step speed and intensity did not have independent associations with mortality.
The large sample size, pedometer usage, and robust adjustment for confounders are all strengths of this study. The limited diversity (sample mostly consisting of elderly Caucasian females of above average health) limits generalizability.
In-Depth [prospective cohort]: This was a prospective cohort study of women in the United States with a sample size of 16,741 women with a mean age 72 years. Steps per day were measured with pedometers over 7 days. Participants were included from the Women’s Health Study (WHS), which ran from 1992 – 2004 in the United States. This study included survivors who consented between 2011 and 2015 who wore and returned pedometers as instructed. Only patients who wore devices for 10+ hours daily on 4+ out of a possible 7 days were included. Data was also collected on patient sociodemographic characteristics, health habits, personal medical history, and family medical history. Women were grouped into quartiles of steps taken (Medians were respectively 2718, 4363, 5905, and 8442) and steps per day was analyzed both as a continuous variable and as quartiles. Primary outcome as mortality. Mean step count was 5499 steps/day. Average follow up was 4.3 years. There were 504 women who died during follow up (3%). The adjusted hazard ratios for mortality in order of increasing step count quartile were: 1.00, 0.59, 0.54, and 0.42 (p<0.01). When evaluated as a continuous variable, adjusted hazard ratio declined by 15% for every 1000 steps, with effect peaking at 7500 steps. Step speed and intensity did not have significant independent associations with mortality.
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