The Implications of Power Mobility on Body Weight in a Veteran Population
Background: The prevalence of obesity is increasing in the United States. A common concern among health care providers is that prescribing a power mobility device (PMD) may decrease physical activity and lead to obesity and increasing morbidity. This study analyzes the effect of PMD prescriptions over a 2-year period on body mass index (BMI) and body weight in a population of veterans both as a whole and in BMI/age subgroups.
Methods: Prosthetics department medical records of veterans who received PMDs for the first time between January 1, 2011 and June 30, 2012 were reviewed. Of 399 records reviewed, 185 veterans met criteria for data analysis. The primary outcome measure was the change in BMI and body weight from time 1 (date of PMD prescription) to time 2 (2 years later).
Results: There was a significant decrease in BMI and weight in the first 2 years after receiving a PMD prescription. However, age moderated the relationship between BMI and time.
Conclusions: PMD use does not seem to be associated with significant weight change. Further studies using control groups and assessing comorbidities are needed.
Results
Of the 185 veterans, 181 were male (98%); mean age was 67.3 years (range, 26-90); and 55% were aged ≥ 65 years. Musculoskeletal disorders (41.6%) were the most common primary indication for a PMD, followed by pulmonary disorders (25.4%) and cardiovascular disorders (23.8%) (Table 1).
There was a significant decrease in BMI in the first 2 years after receiving a PMD prescription for the first time (estimated marginal means: 31.5 to 30.9 , P = .02). However, age moderated the relationship between BMI and time F[1, 183] = 12.14, P = .001, partial η2 = .06 (Table 2). The 101 subjects aged > 65 years experienced a significant decrease in BMI (estimated marginal means: 30.3 to 29.1, P < .001), whereas the 84 patients aged < 65 years experienced a slight and nonsignificant increase in BMI (estimated marginal means: 32.9 to 33.1, P = .45). BMI was significantly higher for subjects aged < 65 years at Time 1 (F[1, 183] = 4.32, P = .04, partial η2 = .02) and at Time 2 (F[1, 183] = 11.04, P = .001, partial η2 = .06).
Similarly, there was a significant decrease in weight in the first year after receiving a PMD prescription with a change in mean weight from 219.0 to 215.3 lb (P = .3). Again, age moderated the relationship between weight and time (F = 12.81; P < .001; partial η2 = .07). Individuals aged ≥ 65 years experienced a significant decrease in weight (estimated marginal means = 209.4 to 200.9; P < .001), whereas those aged < 65 years experienced a slight and nonsignificant increase in weight (230.6 to 232.6; P = .36). Weight was significantly higher for individuals aged < 65 years at time 1 (F = 5.34; P = .02; partial η2 = .03) and at time 2 (F = 12.18; P = .001; partial η2 = .06).
The percentage of those who were obese (BMI ≥ 30) at time 1 (49.7%) did not significantly change at time 2 (46.5%) (exact McNemar test, P = .26). Similarly, there was no significant change in obesity from time 1 to time 2 for those aged < 65 years (exact McNemar test P = .69) or for those aged ≥ 65 years (exact McNemar test P = .06). Obesity at time 2 was significantly more common in those aged < 65 years (56.0%) than those aged ≥ 65 years (38.6%), χ2 [1] = 5.54; P = .02. Obesity at time 1 did not differ between those aged < 65 years (53.6%) and aged ≥ 65 years (46.5%), η2 [1] = 0.9; P = .34. Obesity moderated the relationship between weight and time (F = 5.10; P = .03; partial η2= .03) in that obese individuals experienced a significant decrease in weight with estimated marginal means (SE) = 264.5 (4.51) to 257.4 (4.97); F = 11.32; P < .001; partial η2 = .06), whereas nonobese individuals had no weight change with estimated marginal means (SE) = 174.0 (4.48) to 173.61 (4.94); F = .03; P < .86; partial η2< .01).
Discussion
This study demonstrated a significant decrease in both weight and BMI at 2 years after the initiation of a PMD in patients aged < 65 years. No significant change was found for obesity rates. However, veterans who met criteria for obesity at the time of PMD prescription saw a significant decrease in their weight at 2 years compared with those who were nonobese.
VHA supports power mobility when there is a clear functional need that cannot be met by rehabilitation, surgical, or medical interventions to enhance veterans’ abilities to access medical care, accomplish necessary tasks of daily living, and to have greater access to their communities. Though limited by strength of association, studies involving PMD users generally found improvement in reported functional outcomes and overall satisfaction with PMD use based on a systematic review.13 Nonetheless, there is an implicit concern among providers that a PMD prescription, by limiting physical activity, may exacerbate obesity trends in potentially high-risk individuals.
However, a controversy exists about whether increasing physical activity alone leads to weight loss. A 2007 study followed 102 sedentary men and 100 women over 1 year randomized to moderately intensive exercise for 60 minutes, 6 days a week vs no intervention.14 The men lost an average of 4 pounds, and women lost an average of 3 pounds after 1 year. The Women’s Health Study divided 39,876 women into high, medium, and low levels of exercise groups. After 10 years, the intense exercise group did not have any significant weight loss.15
Our study was consistent with existing literature in that a PMD prescription did not correlate with weight gain.2,9 In our veteran population aged ≥ 65 years, we observed an opposite trend of weight loss after PMD prescription. Of note, studies have shown that peak body weight occurs in the sixth decade, remains stable until about aged 70 years, and then slowly decreases thereafter, at a rate of 0.1 to 0.2 kg per year.16 This likely explains some of the weight loss trend we observed in our study of veterans aged ≥ 65 years. Possible additional explanations include improved access to health care and to more nutritional foods that promote general health and well-being.
