Moving beyond Sedentarism in CKD

• sedentarism
• chronic kidney disease
• physical activity
• sedentary behavior
• exercise
• accelerometer
• walking
• mobility
• physical function
• physical performance

Physical inactivity and sedentarism are strongly associated with adverse health outcomes across multiple populations (1,2). Sedentary behavior is considered a clinically important state on the low end of the physical activity continuum, representing a distinct risk marker for metabolic syndrome, diabetes, and poor health outcomes (2). It is defined as any waking behavior characterized by the expenditure of 1.5 metabolic equivalents of task or less in a sitting, reclining, or lying posture (2). This level of energy expenditure is barely above the resting energy expenditure of one metabolic equivalent of task. Research studies have operationalized these sedentary behaviors as self-reported daily television viewing time, or as measured low counts on digital actigraphy (accelerometry).

Populations with CKD suffer a substantially greater burden of physical inactivity and sedentary behavior than the general population, translating into greater risk of mortality (3,4). Despite evidence suggesting that the hazardous effects of sedentary behavior are more pronounced in physically inactive people (5), few studies have specifically targeted reductions in sedentary behavior in these vulnerable populations. Instead, the majority of interventions have targeted improvements in physical activity through structured physical activity interventions in the form of in-center, gym-based aerobic and resistance training.

Structured physical activity interventions targeting improvements in moderate to vigorous physical activity with supervised aerobic and resistance training have been the traditional modality to improve physical function and fitness. However, these interventions may be resource intensive, with designs limited by lack of appropriate attention control group, restricted eligibility criteria, difficulties with subject retention, and waning interest over time, limiting their validity and generalizability. Although multiple small randomized trials have demonstrated the efficacy of supervised training in improving patient-reported and performance-based outcomes in persons living with CKD, their effectiveness in programs of scale remains to be proven.

Home-based or hybrid physical activity interventions primarily focused on walking are effective for maintaining or improving physical performance in older adults and adults living with advanced kidney disease (6,7). The Lifestyle Interventions and Independence for Elders (LIFE) study is perhaps the largest randomized controlled trial of a structured physical activity program versus attention control interventions demonstrating effectiveness in reducing persistent mobility disability in sedentary older adults with physical limitations. Sedentary was defined by 125 or fewer minutes of self-reported activity per week and physical limitations defined by low short physical performance battery scores of four to nine (maximal score is 12). The primary intervention in the LIFE study was progressive walking. Walking interventions have also demonstrated benefits in patients living with kidney failure treated with hemodialysis. One large randomized controlled trial of a 6-month home-based progressive walking intervention among persons with kidney failure treated with hemodialysis demonstrated meaningful improvement in 6-minute walk distance and muscle strength (7). In particular, home-based interventions targeting physical inactivity or sedentary behavior are promising due to their simplicity, feasibility, and improved generalizability to the broader population of sedentary patients living with CKD.

The American College of Sports Medicine recently provided a framework for prescribing exercise as medicine in chronic disease built on the foundation of encouraging patients to sit less and to move more (8). Reduction in sedentary behavior is considered the foundation for any exercise prescription for all ages and populations with chronic illness. Evidence in support of encouraging movement comes from observational studies indicating that a greater number of steps per day is inversely associated with risk of mortality independent of walking intensity (cadence) (9).

The pilot randomized controlled trial targeting sedentary behavior in CKD by Lyden et al. (10), featured in this issue of CJASN, is a significant contribution toward addressing the burden of sedentarism in CKD. This trial compared an intervention centered on encouraging participants to sit less and move more (SLIMM) with standard of care encouragement to achieve a goal of 150 min/wk of moderate to vigorous physical activity in patients with stages 2–5 CKD. The SLIMM group received detailed education and feedback centered on their accelerometer summaries and when they were most sedentary every 4 weeks up to 24 weeks. Participants were instructed to get up from a sedentary posture at least once per hour to encourage light physical activity during waking hours and given concrete examples of these activities both at work and home. The standard of care group received counseling on increasing moderate to vigorous physical activity with follow-up to collect accelerometry data at 8, 16, and 24 weeks. Eligible participants had a gait speed of ≥0.7 m/s and were able to walk ≥250 m on 6-minute walk tests. To put this in perspective, slow gait speed is considered <0.8 m/s, with dysmobility considered ≤0.6 m/s, and 6-minute walk distance <350 m incurs greater risk of mortality. The study population resembled the general population of adults with CKD in its age distribution, body mass index, and prevalence of diabetes.

The investigators are to be commended for demonstrating the feasibility and efficacy of a program focusing on a SLIMM approach targeting sedentarism in CKD. The study achieved a respectable 83% retention over 24 weeks in the intervention. Although there was a strong suggestion of improvements in primary outcomes (sedentary and stepping duration) and a key secondary end point (steps per day) in the SLIMM group, the study was challenged by waning of the effects of SLIMM over time. The SLIMM group had an increase in steps per day and reduction in sedentary time over 20 weeks, whereas no meaningful change was observed in these outcomes in the standard of care arm. Unfortunately, the differences between the SLIMM and standard of care groups markedly attenuated at 24 weeks, contributing to a reduction in overall treatment effect of the SLIMM intervention on these primary outcomes. Notwithstanding these findings, there was an improvement in secondary end points evidenced by decreased percentage of body fat and body mass index in the SLIMM group. Although the SLIMM intervention failed to improve physical performance compared with the standard of care, there was suggestion of steady improvements in 6-minute walking distance in the SLIMM group over time. When interpreting these comparative effects, it is important to note that the SLIMM group received disproportionately greater attention, including biofeedback using accelerometry, compared with the standard of care arm. This limitation, however, does not detract from the significance of a relatively simple strategy on the basis of a SLIMM approach to improve physical activity in persons living with CKD.

Findings from the current randomized controlled trial of SLIMM intervention informs future large-scale interventions targeting improvements in physical activity among persons living with CKD in several meaningful ways. First, post hoc exploratory analysis demonstrated the importance of including a SLIMM approach to any physical activity intervention. Specifically, the SLIMM group had a much greater likelihood of achieving clinically meaningful improvements in step duration (≥32 min/d) compared with standard of care. Second, those who failed to achieve clinically meaningful improvements in step duration had poor baseline physical performance (6-minute walk test) and appeared to have greater body fat and more severe kidney disease (stages 3b–5). This may indicate that interdisciplinary rehabilitative approaches including a SLIMM approach would be most appropriate for those with more severe mobility impairment and more severe kidney disease. Third, the waning effect of the intervention noted between weeks 20 and 24 underscores the need for integrating sustained patient engagement with continuous feedback and reinforcement. More attention and counseling may be necessary to ensure sustained improvements in physical activity by addressing deficits in self-confidence and motivation.

Addressing the challenges of initiating and maintaining improved physical activity may require future interventions to integrate knowledge from social cognitive theory focusing on improving self-efficacy, capacity, and motivation. Social cognitive theory suggests that initiation and maintenance of healthy physical activity behaviors are a function of expectations about one’s perceived ability to perform the healthy behavior (self-efficacy) and realistic expectations of the outcome from performing the healthy behavior (outcome expectation). Motivational interviewing is one potential tool improving self-efficacy while helping to maintain healthy behavior. A recent study of postacute coronary syndrome patients demonstrated the efficacy of motivational interviewing on improving daily step counts, levels of moderate to vigorous physical activity, and positive affect (11). This particular intervention was centered on the overall “5 A’s” strategy (ask, advise, assess, assist, and arrange) of positive psychology and motivational interviewing. As part of this strategy, providers (1) assess health behaviors and barriers to maintaining a healthy lifestyle (ask); (2) provide clear, specific, and personalized advice on reducing sedentary behavior and improving physical activity (advise); (3) select treatment goals and approach on the basis of the patient’s needs (assess); (4) aid the patient in achieving agreed upon goals through self-help, counseling, and medical treatment as appropriate (assist); and (5) schedule follow-up contacts to provide ongoing assistance (arrange).

Kidney health providers are uniquely positioned to assist sedentary persons living with CKD in making meaningful lifestyle change and, thus, improving their overall health and quality of life. The kidney health community would benefit from future pragmatic clinical trials of a multidisciplinary approach to improving health and wellness in populations living with CKD. We now know that this approach should also focus on reducing sedentary behavior and include positive psychology and motivational components to address self-efficacy and motivation, helping to increase the likelihood of a sustained effect on health behavior.

• Copyright © 2021 by the American Society of Nephrology