Lifestyle change and mobility in obese adults with type 2 diabetes

Abstract

Background: Adults with type 2 diabetes mellitus often have limitations in mobility that increase with age. An intensive lifestyle intervention that produces weight loss and improves fitness could slow the loss of mobility in such patients.

Methods: We randomly assigned 5145 overweight or obese adults between the ages of 45 and 74 years with type 2 diabetes to either an intensive lifestyle intervention or a diabetes support-and-education program; 5016 participants contributed data. We used hidden Markov models to characterize disability states and mixed-effects ordinal logistic regression to estimate the probability of functional decline. The primary outcome was self-reported limitation in mobility, with annual assessments for 4 years.

Results: At year 4, among 2514 adults in the lifestyle-intervention group, 517 (20.6%) had severe disability and 969 (38.5%) had good mobility; the numbers among 2502 participants in the support group were 656 (26.2%) and 798 (31.9%), respectively. The lifestyle-intervention group had a relative reduction of 48% in the risk of loss of mobility, as compared with the support group (odds ratio, 0.52; 95% confidence interval, 0.44 to 0.63; P<0.001). Both weight loss and improved fitness (as assessed on treadmill testing) were significant mediators of this effect (P<0.001 for both variables). Adverse events that were related to the lifestyle intervention included a slightly higher frequency of musculoskeletal symptoms at year 1.

Conclusions: Weight loss and improved fitness slowed the decline in mobility in overweight adults with type 2 diabetes. (Funded by the Department of Health and Human Services and others; ClinicalTrials.gov number, NCT00017953.).

Figure 1. Model of Four States of Clinical Disability

In state 1 (good mobility), participants had some difficulty in performing vigorous physical activities. In state 2 (mild mobility-related disability), participants had problems in bending and long-distance walking. In state 3 (moderate mobility-related disability), participants had deficits in many tasks and some deterioration in the ability to climb stairs and engage in moderately demanding activities. In state 4 (severe limitations), participants had difficulty in nearly all tasks. In each category, the longer the horizontal bar, the higher the probability that participants could perform that task without difficulty.

Figure 2. Prevalence of the Four States of Clinical Disability during the 4-Year Study

The numbers in each color block are the percentages of participants at each state of mobility-related disability among those receiving diabetes support and education and those receiving an intensive lifestyle intervention. Values at follow-up visits for years 1 to 4 have been adjusted for baseline values.

Figure 3. Path Diagram for Mediational Model

The four solid arrows represent significant indirect effects, and the dashed arrow represents a marginally significant direct effect of the intervention on mobility after adjustment for the mediators. The coefficients and 95% confidence intervals are positioned at the middle of each arrow; those on the arrows leading from the intervention to each mediator represent the percent weight loss and fitness improvement owing to the intervention. The coefficients for the effect that weight loss and improved fitness had on disability show that for every 1% loss in weight there was a 7.3% reduction in the odds ratio for disability [(1.00 − 0.927) × 100], and for every 1% improvement in fitness [(1.00 − 0.986) × 100], the odds ratio was reduced by 1.4%.