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Higher daily step counts strongly associated with lower mortality risk

A study has found that higher daily step counts were associated with lower mortality risk from all causes. The research team, which included investigators from the National Cancer Institute (NCI) and the National Institute on Aging (NIA), both parts of the National Institutes of Health, as well as from the US Centres for Disease Control and Prevention (CDC), also found that the number of steps a person takes each day, but not the intensity of stepping, had a strong association with mortality.

“While we knew physical activity is good for you, we didn’t know how many steps per day you need to take to lower your mortality risk or whether stepping at a higher intensity makes a difference,” said Dr Pedro Saint-Maurice, of NCI’s division of cancer epidemiology and genetics, first author of the study. “We wanted to investigate this question to provide new insights that could help people better understand the health implications of the step counts they get from fitness trackers and phone apps.”

Previous studies have been done on step counts and mortality. However, they were conducted primarily with older adults or among people with debilitating chronic conditions. This study tracked a representative sample of US adults aged 40 and over; approximately 4,800 participants wore accelerometers for up to seven days between 2003 and 2006. The participants were then followed for mortality through 2015 via the National Death Index. The researchers calculated associations between mortality and step number and intensity after adjustment for demographic and behavioural risk factors, body mass index, and health status at the start of the study.

They found that, compared with taking 4,000 steps per day, a number considered to be low for adults, taking 8,000 steps per day was associated with a 51% lower risk for all-cause mortality (or death from all causes). Taking 12,000 steps per day was associated with a 65% lower risk compared with taking 4,000 steps. In contrast, the authors saw no association between step intensity and risk of death after accounting for the total number of steps taken per day.

“At NIA, we’ve long studied how exercise is important for older adults, and it’s good to see further evidence from a large study with a broad sample that the main thing is to get moving for better overall health as we age,” said Dr Eric Shiroma, a co-author and NIA Intramural Research Programme scientist.

In analyses by sub-groups of participants, the authors found that higher step counts were associated with lower all-cause death rates among both men and women; among both younger and older adults; and among white, black, and Mexican-American adults. In secondary outcomes of the study, higher step counts were also associated with lower rates of death from cardiovascular disease and cancer.

Data collection was conducted through the CDC’s National Health and Nutrition Examination Survey (NHANES), a programme of studies designed to assess a nationally representative sample of the health and nutritional status of adults and children in the US.

The researchers were surprised they didn’t find an association between higher stepping intensity and all-cause mortality after adjusting for the total number of steps per day. Because few studies have investigated an association between mortality and intensity among adults going about their daily lives, the study authors wrote that future studies of walking intensity and mortality are warranted.

Although the study authors controlled for factors that could have affected the results, the study is observational and cannot prove causality. Nevertheless, their findings are consistent with current recommendations that adults should move more and sit less throughout the day. Adults who do any amount of physical activity gain some health benefits. For even greater health benefits, adults are recommended to get at least 150 minutes of moderate-intensity physical activity per week.

“Being physically active has many benefits, including reducing a person’s risk of obesity, heart disease, type 2 diabetes, and some cancers. And on a daily basis, it can help people feel better and sleep better,” said Dr Janet Fulton, of CDC’s division of nutrition, physical activity, and obesity. “CDC is working with communities and partners across the country, as part of the Active People – Healthy Nation initiative, to make it easier, safer, and more convenient for people to be active in their own communities."

Abstract
Importance: It is unclear whether the number of steps per day and the intensity of stepping are associated with lower mortality.
Objective: Describe the dose-response relationship between step count and intensity and mortality.
Design, Setting, and Participants: Representative sample of US adults aged at least 40 years in the National Health and Nutrition Examination Survey who wore an accelerometer for up to 7 days (from 2003-2006). Mortality was ascertained through December 2015.

Exposures: Accelerometer-measured number of steps per day and 3 step intensity measures (extended bout cadence, peak 30-minute cadence, and peak 1-minute cadence [steps/min]). Accelerometer data were based on measurements obtained during a 7-day period at baseline.
Main Outcomes and Measures: The primary outcome was all-cause mortality. Secondary outcomes were cardiovascular disease (CVD) and cancer mortality. Hazard ratios (HRs), mortality rates, and 95% CIs were estimated using cubic splines and quartile classifications adjusting for age; sex; race/ethnicity; education; diet; smoking status; body mass index; self-reported health; mobility limitations; and diagnoses of diabetes, stroke, heart disease, heart failure, cancer, chronic bronchitis, and emphysema.

Results: A total of 4840 participants (mean age, 56.8 years; 2435 [54%] women; 1732 [36%] individuals with obesity) wore accelerometers for a mean of 5.7 days for a mean of 14.4 hours per day. The mean number of steps per day was 9124. There were 1165 deaths over a mean 10.1 years of follow-up, including 406 CVD and 283 cancer deaths. The unadjusted incidence density for all-cause mortality was 76.7 per 1000 person-years (419 deaths) for the 655 individuals who took less than 4000 steps per day; 21.4 per 1000 person-years (488 deaths) for the 1727 individuals who took 4000 to 7999 steps per day; 6.9 per 1000 person-years (176 deaths) for the 1539 individuals who took 8000 to 11 999 steps per day; and 4.8 per 1000 person-years (82 deaths) for the 919 individuals who took at least 12 000 steps per day. Compared with taking 4000 steps per day, taking 8000 steps per day was associated with significantly lower all-cause mortality (HR, 0.49 [95% CI, 0.44-0.55]), as was taking 12 000 steps per day (HR, 0.35 [95% CI, 0.28-0.45]). Unadjusted incidence density for all-cause mortality by peak 30 cadence was 32.9 per 1000 person-years (406 deaths) for the 1080 individuals who took 18.5 to 56.0 steps per minute; 12.6 per 1000 person-years (207 deaths) for the 1153 individuals who took 56.1 to 69.2 steps per minute; 6.8 per 1000 person-years (124 deaths) for the 1074 individuals who took 69.3 to 82.8 steps per minute; and 5.3 per 1000 person-years (108 deaths) for the 1037 individuals who took 82.9 to 149.5 steps per minute. Greater step intensity was not significantly associated with lower mortality after adjustment for total steps per day (eg, highest vs lowest quartile of peak 30 cadence: HR, 0.90 [95% CI, 0.65-1.27]; P value for trend = .34).
Conclusions and Relevance: Based on a representative sample of US adults, a greater number of daily steps was significantly associated with lower all-cause mortality. There was no significant association between step intensity and mortality after adjusting for total steps per day.

Authors
Pedro F Saint-Maurice; Richard P Troiano; David R Bassett Jr; Barry I Graubard; Susan A Carlson; Eric J Shiroma; Janet E Fulton; Charles E Matthews

[link url="https://www.cancer.gov/news-events/press-releases/2020/daily-step-count-mortality"]National Cancer Institute material[/link]

[link url="https://jamanetwork.com/journals/jama/fullarticle/2763292?guestAccessKey=9f6744af-eb6c-4e03-9bca-d85492e1acab&utm_source=For_The_Media&utm_medium=referral&utm_campaign=ftm_links&utm_content=tfl&utm_term=032420"]JAMA abstract[/link]

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