Our study is the first analysis of factors associated with sustained walking within a cohort of managed care patients with diabetes and adds several key findings to the literature. We found that clinical factors such as obesity and symptoms of pain were associated with a moderately lower likelihood of sustained walking, as was age ≥65 years, use of antiglycemic medications, and the development of a major new comorbidity. We did not find an association between self-reported neighborhood variables and the likelihood of sustained walking.
Approximately 65–70% of participants in our study sustained walking over several years, more than have been observed in the majority of walking intervention trials,26
but similar to populations of community-dwelling individuals who are walking on their own.5
Our analytic sample was drawn from participants in the second and third waves of a longitudinal study and, therefore, represented a somewhat select, motivated, and active group compared to the overall population. However, a substantial minority of TRIAD participants did not sustain walking, and identifying preventable or treatable reasons why relatively motivated patients may stop walking is clinically important. Sustained physical activity is important for this population, as it leads to reductions in visceral fat that may in turn be associated with a lower risk of adverse cardiovascular outcomes.7–9
The identified relationship between pain and sustained walking is particularly noteworthy. Other investigators have shown that over 50% of patients with diabetes report pain that interferes with usual exercise regimens.27
We found that patients with new pain since baseline were particularly unlikely to sustain walking, which supports the importance of regular screening for pain among active individuals with diabetes. This is crucial because clinicians may not be aware of the presence or severity of symptoms.28
Almost a quarter of patients with chronic pain do not inform their providers,29
and many of these people choose to self-manage their pain, using suboptimal strategies.30
Appropriate pain treatment, using analgesic and nonanalgesic modalities with stepped-up therapy as needed may improve quality of life and promote continued physical activity among patients with diabetes.
Obesity has been previously linked with inactivity in cross-sectional studies among populations with diabetes,25,31
but our longitudinal findings show that obese patients who are actively walking are less likely to sustain that behavior than are patients of normal weight or those who are overweight. There are several possible explanations for our findings, such as potential lower self-efficacy for physical activity among the obese,32
or physiologic limitations, such as higher oxygen consumption by obese individuals at a given activity level compared with individuals of normal weight.33
Efforts to prevent overweight individuals from gaining weight and ultimately progressing to obesity may help them remain active.
Several diabetes medications can lead to weight gain, particularly insulin and thiazolidinediones (TZDs).34
Well-meaning clinicians may inadvertently contribute to their patients’ obesity through their choice of drug therapy. Regimens with less potential for weight gain, such as the use of metformin in combination with TZD therapy (as opposed to TZD monotherapy), decrease the potential for obesity. Whereas aggressive glycemic control is a primary concern in the treatment of patients with diabetes, thoughtful prescribing patterns along with diet and exercise will help to prevent weight gain and thereby may facilitate continued walking over the long-term.
Our finding that patients who sustain a new comorbidity are less likely to sustain walking is not surprising. The development of a major comorbid event such as a myocardial infarction can be associated with the onset or progression of disability, limiting the capacity for physical activity, which in turn increases the risk for future comorbid events. Intensive treatment with multiple drugs to achieve tight control of blood pressure and glucose levels and reduce low-density lipoprotein (LDL) cholesterol significantly reduces macrovascular complications of diabetes such as myocardial infarctions and cerebrovascular accidents.34–36
Unfortunately, these goals have proven difficult to achieve in real-life settings.37
Our findings support the importance of finding viable ways to increase the use of multiple drugs to treat patients with diabetes.
Among the demographic variables we examined, only age was associated with sustained walking with patients aged 65 years and over the least likely to keep walking. This was not surprising, as any characteristics of age related to inactivity, such as falls or the fear of falling, will only increase during a longitudinal study. Several evidence-based interventions involving physical activity for older adults that address these types of barriers are being actively translated to “real-world” community settings.38–40
We did not find statistical evidence to support our hypothesis that patients with diabetes who have preexisting depressive symptoms or develop new depressive symptoms would be less likely to sustain walking. Major depression has been associated in cross-sectional analyses with higher rates of physical inactivity among patients with diabetes,41,42
but the relationship between depression and physical inactivity is likely bidirectional.43
Excluding nonwalkers from the study cohort may, therefore, have contributed to a weaker link between depression and physical activity than has been seen in earlier cross-sectional analyses. In addition, we had relatively few patients with depressive symptoms in the overall study cohort and we may have lacked power to detect a difference in sustained walking behavior.
We found no evidence to support an association of “activity-friendly” neighborhood characteristics such as adequate lighting and minimal litter with sustained walking. As with depressive symptoms, we had limited power to identify differences in walking behavior related to these variables. Because we only examined patients already walking at baseline, our results do not reflect whether adverse neighborhood conditions are negatively associated with the initiation of walking.
Our study has several limitations. First, we classified patients as walkers or nonwalkers from self-reported minutes walked per day at 2 points in time, and thus actual activity may have been misreported. However, this is unlikely to have produced a directional bias, as the predictors of sustained walking we identified are unlikely to be associated with the likelihood of overreporting or underreporting walking activity. Second, follow-up measures of pain and depression were collected at the same time as the measure of sustained walking, so we can report associations but are unable to determine causality. Third, we lacked data on physical activities other than walking, so participants could have substituted other moderate-intensity activities rather than discontinuing physical activity altogether. Finally, we were unable to identify those patients who walked at least 150 minutes/week but did not walk every day, may not have captured all participants who were walking regularly at baseline, and were unable to distinguish between walking for exercise and walking for lifestyle-related activities.
Our analysis is one of the first to examine sustained walking behavior in a large sample of patients with diabetes. We found that patients with diabetes were somewhat less likely to sustain walking when they were experiencing symptoms of pain. Obesity, the development of new comorbidities, and advanced age were also associated with a moderately lower likelihood of sustained walking. We did not identify associations between depressive symptoms or neighborhood characteristics and sustained walking, but this may have been because of the study limitations. Whereas controlled intervention studies are needed, our findings suggest that treating pain and preventing obesity and macrovascular events may be associated with higher rates of sustained walking among patients with diabetes.