The Right Speed
The authors first categorized walking speed into four prespecified levels: Easy or casual (< 2 mph or 3.2 km/h), average or normal (2-3 mph or 3.2-4.8 km/h), fairly brisk (3-4 mph or 4.8-6.4 km/h), and very brisk or brisk/striding (> 4 mph or > 6.4 km/h).
Four cohort studies with 6,520 cases of T2D among 160,321 participants reported information on average or normal walking. Participants with average or normal walking were at a 15% lower risk for T2D than those with easy or casual walking (RR = 0.85 [95% CI, 0.70-1.00]; RD = 0.86 [1.72-0]). Ten cohort studies with 18,410 cases among 508,121 participants reported information on fairly brisk walking. Those with fairly brisk walking were at a 24% lower risk for T2D than those with easy or casual walking (RR = 0.76 [0.65-0.87]; I2 = 90%; RD = 1.38 [2.01-0.75]).
There was no significant or credible subgroup difference by adjustment for the total physical activity or time spent walking per day. The dose-response analysis suggested that the risk for T2D decreased significantly at a walking speed of 4 km/h and above.
Study Limitations
This meta-analysis has strengths that may increase the generalizability of its results. The researchers included cohort studies, which allowed them to consider the temporal sequence of exposure and outcome. Cohort studies are less affected by recall and selection biases compared with retrospective case–control studies, which increase the likelihood of causality. The researchers also assessed the credibility of subgroup differences using the recently developed ICEMAN tool, calculated both relative and absolute risks, and rated the certainty of evidence using the GRADE approach.
Some shortcomings must be considered. Most of the studies included in the present review were rated as having a serious risk for bias, with the most important biases resulting from inadequate adjustment for potential confounders and the methods used for walking speed assessment and diagnosis of T2D. In addition, the findings could have been subject to reverse causality bias because participants with faster walking speed are more likely to perform more physical activity and have better cardiorespiratory fitness, greater muscle mass, and better health status. However, the subgroup analyses of fairly brisk and brisk/striding walking indicated that there were no significant subgroup differences by follow-up duration and that the significant inverse associations remained stable in the subgroup of cohort studies with a follow-up duration of > 10 years.
The authors concluded that While current strategies to increase total walking time are beneficial, it may also be reasonable to encourage people to walk at faster speeds to further increase the health benefits of walking.”
This article was translated from JIM, which is part of the Medscape Professional Network. A version of this article appeared on Medscape.com.