Walking speed: the sixth vital sign
Walking speed predicts a host of health outcomes and it’s easily and reliably measured with minimal equipment and cost. Given the ability of walking speed to predict health, two physical therapy researchers called walking speed the sixth vital sign, accompanying the five routinely measured vital signs of blood pressure, pulse, respiration, temperature, and pain.
An updated and expanded version of sixth vital sign article confirmed the earlier claim and provided cut points for various functional characteristics. For example, people with a normal walking speed of 0.9 mph or slower have increased risk for functional impairment. People with a normal walking speed of 1.6 mph or slower have increased risk for death, hospitalizations and falls. And people with a normal walking speed of 2.2 mph or slower have increased risk of cognitive decline in 5 years. People with a normal walking speed of 2.9 mph and faster are extremely fit.
You can easily measure your normal walking pace by measuring a straight, flat course of 30 feet (10 yards) on a sidewalk. Start walking 10 yards before the course. When you cross the starting point, a friend starts a stopwatch then stops it when you cross the end of the course. Divide the conversion factor 20.56 by your time in seconds to find you normal walking speed in miles per hour.
Walk faster, lower risk of cardiovascular disease
Early studies showed that moderate-intensity physical activity reduced the risk of cardiovascular disease. Given that walking is an accessible form of physical activity, researchers in the UK conducted a systematic review and meta-analysis of 18 longitudinal cohort studies to see if walking pace and volume were associated with reduced risk of cardiovascular disease and all-cause mortality. Data from 14 of the studies showed that highest walking category (either volume or intensity) predicted significant 32 and 31 percent lower risks of cardiovascular disease for men and women, respectively. For all-cause mortality, the highest walking category (volume or intensity) predicted significant 34 and 28 percent lower risks for men and women, respectively. Subgroup analyses revealed that higher walking intensity compared to higher walking volume resulted in greater reduced risk of cardiovascular disease and all-cause mortality combined, 48 and 26 percent, respectively. A less impressive result appeared for moderate walking pace compared to lower walking volume (39 and 10 percent lower risk, respectively). Finally, a dose-response effect appeared among the highest, intermediate, and lowest levels of walking volume and intensity. This review supports the recommendation to get at least 150 minutes of moderate-intensity of physical activity per week.
Walk faster, live longer
In the US, the average remaining life span at age 66 is 18.6 years for a man and 20.8 years for a woman, according to the Social Security Administration web site. We all know that actual results vary, but a widely validated method to personalize the estimate of remaining life span does not exist. A group of scientists wondered if normal gait speed, an easily measured personal attribute, is significantly associated with mortality. The researchers used data from nine studies published between 1986 and 2000 to test this idea. The cohorts included persons age 65 or older for which gait speed data were available. Gait speed was measured on courses ranging from eight feet to six meters (18.6 feet) long. The subjects (N=34,485) were followed for 6 – 21 years.
Predicted years of remaining life span for both sexes increased as gait speed increased, with a gait speed of 0.8 meters per second (1.8 mph) associated with the median remaining life expectancy. Another example: At age 75, predicted median survival for a man with a gait speed of 0.4 meters per second (0.9 mph) was just under 6 years, while that for a man with a gait a speed of 1.4 meters per second (3.1 mph) was 15 years. For a woman, the comparable survival estimates were 7.5 and 19 years, respectively. Those are huge differences! Thus, normal gait speed provides a simple measure of overall vitality. Setting a goal to reach and maintain a normal gait speed of, say, 1.4 meters per second (3.1 mph), could motivate older people to be physically active and live longer and better.
Walk faster, live longer in the UK
Previous studies that investigated links between walking pace and risk of mortality did not control for overall levels of physical activity. Thus, the effects of walking pace and overall physical activity were confounded. Researchers used data from 50,225 participants in the Health Survey of England and the Scottish Health Survey to correct this deficiency. Walking pace was self-reported in the present study. After adjusting for overall physical activity and other confounders and compared to participants with a slow walking pace, participants with average or brisk/fast walking pace had significant 20 and 24 percent lower risks, respectively, of all-cause mortality over an average follow-up of 9 years. For cardiovascular-related mortality, the comparable reductions in risk were 33 and 46 percent, respectively. Interestingly, when participants were grouped as under or over age 50 years, the beneficial effects of average or brisk/fast walking remained significant only for the 50 years and older participants. Faster walking pace might reduce risk of death by increasing aerobic fitness. Plus, faster walkers might also be more likely to embrace other healthy lifestyle choices than slow walkers. Of note, walking pace was not related to cancer-related mortality.
Walk faster, lower risk of dementia
Increased physical activity predicts decreased risk of developing dementia later in life. Would faster walking speed of older adults predict decreased risk of developing dementia over time? Researchers in the UK used data from a nationally representative sample of 3,932 community-dwelling older adults aged 50 years or older at baseline in the English Longitudinal Study of Aging to find out. Walking speed was evaluated at baseline and 2 years later as the time required to walk 6 meters at a normal pace. Dementia was evaluated from self-report of a physician diagnosis or from the Informant Questionnaire on Cognitive Decline in the Elderly. After adjusting for confounding factors, participants who had faster walking speeds had a significant 64 percent lower risk of developing dementia during follow-up of up to 13 years. In addition, participants who had a greater decline in walking speed between baseline and 2 years later had a significant 23 percent higher risk of developing dementia independent of changes in cognition.
Walk faster, lower risk of stroke
Stroke is the second leading cause of death globally. Plus, stroke survivors often require intensive treatment and rehabilitation. Wouldn’t it be great if faster walking speed predicted lower risk of stroke? Researchers in China answered this question with a meta-analysis of 8 longitudinal cohort studies that included 135,645 participants with an average age of 64 years followed over a median of 8 years. With walking speed categorized as either low (1.6 km per hour = 1.0 mph) or high (5.6 km per hour = 3.4 mph), participants in the high category had 44 percent lower risk of stroke compared to participants in the low category. When walking speed was grouped in three categories (slow, intermediate, fast), each 1 km per hour (0.6 mph) increase in walking speed predicted a significant 13 percent reduction in risk of stroke in a dose-response manner. These robust results remained after accounting for stroke subtypes, sex, sample size, and duration of follow-up. Increased walking speed might reduce risk of stroke by building aerobic fitness, improving vascular structure in the brain, and reducing systemic inflammation.
Walk faster, lower risk of type 2 diabetes
Medical authorities recommend increased physical activity, such as walking more, to manage type 2 diabetes. Recent evidence suggests that walking at a faster pace can provide a greater physiological response than slower walking. Researchers in Iran and Norway conducted a systematic review and meta-analysis of longitudinal studies to determine if faster walking speed would predict lower risk of type 2 diabetes. Ten cohort studies met the inclusion criteria. As walking speed increased from 1 km per hour (0.6 mph) to 4 km per hour (2.5 mph), the relative risk of type 2 diabetes declined slightly and non-significantly. But from walking speed of 4 km per hour (2.5 mph) to 8 km per our (5.0 mph), the relative risk of type 2 diabetes declined significantly in a step-wise manner from 14 to 41 percent lower. At the fastest walking speed (termed brisk/striding walking), the reduction in the number of type 2 diabetes cases avoided (more than 2 percent) was clinically meaningful. Faster walking might reduce type 2 diabetes risk because of increased, short-term strain on the body, which may lead to improved muscle strength and insulin sensitivity, and reduced systematic inflammation and body fat mass.
What to do
You can’t hear it too often: Keep Moving. In particular, find enjoyable ways to walk every day, rain or shine. My wife, Betsy, and I have a routine of walking briskly for 20 minutes after breakfast, lunch, and dinner every day. We enjoy our walks. We chat with our neighbors. We pet their dogs. We meet new neighbors. We build our aerobic fitness and reduce or postpone our risks of bad health outcomes such as type 2 diabetes, stroke, and dementia. Plus, benefits may be greater for older people like us.
