Increasing ambulatory activity reduces cardiovascular events in patients with impaired glucose tolerance and raised risk, data from the Navigator trial has shown.

The main objective of the original study was to determine whether valsartan or nateglinide prevented cardiovascular events and/or progression of impaired glucose tolerance to overt diabetes. The findings did not show any protective effect from either drug.

However, as well as the original research question posed by the trial, the cohort provided a large amount of prospective data for further analysis.  The current paper, published in the Lancet, analysed the relationship between change in daily ambulatory activity and cardiovascular events.

The trial recruited 9,306 individuals with impaired glucose tolerance from 40 countries between January 2002 and January 2004. Participants also had existing cardiovascular disease or at least one additional cardiovascular risk factor.

Ambulatory activity was assessed by pedometer at baseline and 12 months. The pedometer readings were truncated at 10,000 steps a day, which was taken as the 99th centile. Those reporting zero steps a day at base (n = 343) or follow-up (n = 547) were excluded from analysis. The remainder were divided into groups according to changes of 1,500 steps per day. Average follow-up in the cohort was six years and the endpoints were myocardial infarction, non-fatal stroke or cardiovascular mortality.

Follow-up data were available for 9,018 participants after 12 months.

In 45,211 person-years of follow-up, 531 cardiovascular events occurred. Increased baseline ambulatory activity correlated with a reduction in cardiovascular events, hazard ratio (HR) per 2,000 steps per day 0.90 (95% CI:0.84-0.96). Increased activity from baseline also showed a graded response with increased activity correlating with fewer cardiovascular events, HR 0.92 (95% CI:0.86-0.99).

Put simply, every 2,000 step increment at baseline (roughly 20 minutes a day of moderately paced walking) was associated with a 10% lower risk of a cardiovascular event. Each 2,000-step increase over the 12 months reduced the risk by an additional 8%.

A strength of the study was the large international population of patients with impaired glucose tolerance, and high cardiovascular risk, which should make the results applicable to real life practice.

A weakness was the high number of unusable pedometer recordings.

This study demonstrates the beneficial effect of simple walking, one of the most popular and accessible forms of exercise. Unlike the study recently published which showed no benefit for intensive lifestyle changes in overt diabetes,1 there was a significant protective effect in this group of patients with impaired glucose tolerance. This underlines the growing appreciation of the importance of detecting and targeting those at risk of diabetes.

In common with previous studies, the protective effect of lifestyle, especially exercise is superior to any drug intervention.

Dr Matthew Lockyer