Yoga Improves Functional Gait and Quality of Life for Adults with Diabetic Peripheral Neuropathy: A Pilot Study
Diabetes Mellitus (DM) affects roughly 29.1 million persons in the United States, with up to 50% of people with DM estimated to be effected by Diabetic Peripheral Neuropathy (DPN)[1,2]. Diabetic neuropathies encompass a group of nerve disorders caused by DM. DPN is nerve damage specifically in the arms, hands, legs, and feet, and is the most common type of neuropathy affecting populations with diabetes. The negative effects f DPN include declines in functional gait and quality of life (QoL)[1,3].
Functional gait includes walking speed as well as walking endurance[7,8]. Decreased gait speed has been linked to increased likelihood of death in older adults and has been referred to as the ‘sixth vital sign’[9,10]. In people with DPN, muscle strength and ankle mobility are associated with reductions in gait speed for people with DPN. DM is associated with a reduction in lower leg muscle strength which is correlated with a loss of mobility. Declines in strength and mobilityin DM populations were found to be associated with a loss of health-related quality of life (HRQOL). However, it is notcurrently known if there is a correlation between functional gait (a component of mobility) and HRQOL in DM populations.
Benbow et al. established that quality of life (QoL) was significantly more compromised in individuals with DPN than among individuals with diabetes alone. Furthermore, they found that individuals with DPN were found to have impairments in emotional reactions; energy; pain; physical mobility; and sleep. In people with DPN, decreased QoL has been associated with impairments in sleep; enjoyment of life; mobility; employment; and recreational and social activities.
Yoga is an intervention that empowers persons to progress toward improved health and freedom from disease with the implementation of the practice and philosophy of yoga. In general, yoga has been shown to promote: muscular strength; flexibility; respiratory and cardiovascular function; improved sleep patterns; overall well-being and QoL; and a reduction in stress, anxiety, depression, and pain. As a form of therapy, yoga has been shown to offer beneficial results for individuals with heart failure; stroke; chronic obstructive pulmonary disease; degenerative diseases like Parkinson’s syndrome and muscular dystrophy; post-traumatic stress disorder; balance impairments; and certain psychotic conditions[14-19].
While there has been various research conducted on yoga and its effects on different populations, including those with DM, to our knowledge, there is no research in regards to the possible benefits of yoga for people with DPN[20,21]. The only other mind-body intervention to be previously studied in populations with any type of peripheral neuropathy was Tai Chi. However, according to a 2007 national survey of adults in the United States, conducted by Barnes et al. (2008), on the estimates of complementary and alternative medicine use, yoga was used at a rate almost six times that of Tai Chi. According to these statistics, yoga may be a more familiar and accessible mind/body intervention. Therefore, the objectives of this study were to: 1) examine the associations between functional gait and HRQOL (Neuro-QoL) scores in people with DPN; 2) determine the change in Neuro-QoL scores in participants pre- and post-eight-week yoga intervention; and 3) examine the change in functional gait measures (6-Minute Walk Test, 10-Meter Walk Test) in participants pre- and post-eight-week yoga intervention.
These are planned primary analyses of a non-controlled pretestposttest pilot study to understand the impact of yoga on HRQOL and functional gait in people with DPN.
Recruitment and Participants
This convenience sample was recruited from a pre-existing participant registry from past university research studies involving individuals with DPN, an approved recruitment flyer, diabetic and pain management support groups, a diabetic resource fair, and word of mouth. Inclusion criteria included: diagnosis of DPN; the age of 18+; ability to speak English; ability to communicate; and ability to walk 10 meters with or without a device. People were excluded if they had consistently engaged in yoga for more than one year; were unable to attend twice weekly yoga sessions for eight weeks, or had a terminal illness with life expectancy of <6 months. Human participants’ approval was obtained from the University’s Institutional Review Board; all participants granted written informed consent to take part in the study.
All data were gathered and entered by trained research assistants. All components of the study were conducted at a Rehabilitation Lab in the West. Participants in the study completed a series of physical performance assessments and questionnaires before and after the 8-week yoga intervention. Data collection included demographic information (age, gender, race, educational status) and DPN characteristics ( a type of DM, area of symptoms of DPN, DPN severity measured by Michigan
Neuropathy Screening Instrument [MNSI]). We assessed HRQOL and functional gait.
Variables of Interest
Health-related quality of life
The Neuro-QoL was used to measure HRQOL. It has been shown to fulfill specific requirements for both reliability and validity in assessing HRQOL specific to neurological disorders, including DPN. The test was developed to be applicable to a range of neurological conditions; therefore, the test manual specifies that researchers must consider which of the 17 domains are appropriate to assess within a specific disease population[ 25,26]. A lower score equals better HRQOL. We included the following seven 8-item domains: 1) ability to participate in social roles and activities; 2) depression; 3) fatigue; 4) lower extremity function (mobility); 5) satisfaction with social roles and activities; 6) upper extremity function (fine motor, ADL); and 7) anxiety.
Functional gait encompasses both walking speed and walking endurance[7,8]. Assistive devices were used during the walking assessments as necessary. Gait speed was measured using the 10-Meter Walk Test. This assessment requires individuals to walk as fast as they are comfortably able to for 10 meters. Time to walk the 10 meters were collected and then computed to meters/seconds (m/s) to determine the individual’s gait speed.
Walking endurance was assessed using the Six Minute Walk Test (6MWT), which has been shown to be a valid and reliable measure. The test measures the number of feet walked on a level course in the specified six-minute period of time.
Individuals participated in eight weeks of yoga two times per week and one hour per session. The study included yoga, developed as a therapeutic intervention, for two groups of participants, one group of nine participants and one of six participants. Participants were split into two groups as we felt that a maximum of ten study participants in one group was appropriate; the study staff may not have been able to provide enough attention or assistance if the groups were too large. Additionally, in the group was in the early afternoon and one group was in the late afternoon/early evening to better be able to accommodate busy schedules and participants chose which group to attend. Due to snow, there was a total of 15 sessions participants could have attended. Yoga sessions were completed in a research lab and were all led by one registered yoga teacher (200-hour level). The yoga teacher was a 29-year-old female who is an occupational therapist.
The yoga intervention addressed the following variables in relation to individuals’ DPN: movements to gain awareness of lower and upper limbs; movements outside of their base of support; flexibility and strength at the hips, torso, and lower extremity joints; different head positions; reaching; and lunging. The yoga intervention was developed as a 16 session manual to ensure consistency across both groups. Yoga sessions included modified yoga poses for participants as well as deep breathing exercises and meditation that gradually progressed in difficulty throughout the eight weeks of the yoga intervention (all chair yoga that progressed to standing and floor yoga postures). Chairs were in a circle allowing all individuals to see the teacher. The yoga intervention was delivered in a standardized progression allowing for the yoga to become more challenging and building upon prior skills. A copy of the intervention was sent home in week three if participants wished to practice at home.
All components (postures, breath work, meditation) of the yoga protocol were successfully replicated in both groups (Table 1). The table reflects how the yoga postures progressed for the participants throughout the eight-weeks of the intervention.
Data were entered into a Statistical Package for the Social Sciences (SPSS, Inc. Chicago) Version 22 database for management and analyses. Descriptive statistics were used to describe demographics and DPN characteristics with means, standard deviations, frequencies, and proportions as appropriate and compared from the baseline assessment to the eight-week assessment. Correlations were examined between the Neuro- QoL and functional gait scores (6MWT and 10-Meter Walk Test). A correlation was considered to demonstrate a fair degree of relationship if r =0.25-0.50, a moderate degree of relationship if r=0.50-0.75, or an excellent degree of relationship if r>0.75 (Portney & Watkins, 2000). The Shapiro-Wilk test was used to assess the normality of data. Paired t-tests (or Wilcoxon signed-rank test for non-normal data) were used to assess change between baseline and eight-week assessment variables. A Bonferroni adjustment was used to control for multiple comparisons for the three variables assessed (α= 0.05/3 = 0.0167). We also calculated the percent change between baseline and eight-week assessments for each variable by taking ([Time 1-Time 2]/Time 1) x 100. Additionally, due to our preliminary findings and our interest in the HRQoL domains, we conducted posthoc analyses to further investigate changes in the Neuro-QoL data from the baseline assessment to the eightweek assessment. We completed paired t-tests (or Wilcoxon signed-rank test when appropriate) for the seven individual domain scores of the Neuro-QoL.
Table 1. Protocol for modified postures progressed throughout yoga intervention.
A total of 22 participants with DPN were recruited for this study over a three-month time period. All participants were recruited from a midsized Western town and the surrounding area. Potential participants were screened and found to meet the eligibility criteria. Seven individuals who were recruited did not participate in the study because of conflicts that included: work schedules; lack of child-care; complications with co-morbid conditions; and surgery. Fifteen (68%) individuals participated in the study. The ages of participants ranged from 52-92 years, with the mean age being 66.5±11.34 years. The majority of the participants were female (53.3%), white (80%), and had at least some college education (73.3%). The majority of individuals had Type 2 Diabetes (86.7%) and reported a DPN severity of 6.13±2.56 on the MNSI participant questionnaire and 7.83±1.90 on the MNSI physical foot examination. As per the inclusion criteria, all participants reported DPN (100%), with 100% reporting DPN in their feet, and 60% of individuals reporting DPN symptoms in both their hands and feet. See Table 2 for additional descriptive statistics and DPN specific characteristics.
Table 2. Demographics.
All 15 individuals completed both baseline and eight-week assessments and the yoga intervention. Participants were physically able to complete all planned yoga activities, no injuries were sustained, and no adverse events were reported. Overall, the mean number of yoga sessions completed were 12.33±1.91, with a range of 9-15 sessions. Yoga sessions were missed because of sickness, family commitments, scheduling conflicts, doctors’ appointments, and out-of-town travel.
The eight-week assessment scores demonstrated a fair correlation between both the Neuro-QoL and the 6MWT, as well as the Neuro-QoL and the 10-Meter Walk Test (6MWT, r=0.487, p=0.065; 10-Meter Walk Test, r=0.420, p=0.119). Overall, the participants in the study demonstrated improvements in multiple variables. See Table 3 for the changes in variables between baseline and eight-week assessment scores.
* As appropriate, p-values were calculated using Paired Sample T-tests for normal data and non- arametric Wilcoxon signed-rank test for non-normal data.
†Significant after Bonferroni correction (α=.05/3=.0167)
Table 3. Change between baseline and 8-week assessment scores.
Neuro-QoL overall scores, in which lower scores are reflective of better HRQOL, decreased by 8% demonstrating improvement after eight weeks of yoga (110.20±31.68 vs. 101.47±27.75, p=0.054). The number of feet walked in the 6MWT significantly increased by 15% (1018.48±406.99 vs. 1167.18±447.75, p=0.014) with an average improvement of 148.7 feet. In regards to the 10-Meter Walk Test, speed (m/s) significantly increased after eight weeks of yoga by 23% (0.74±0.25 vs. 0.91±0.28, p<0.001), with an average improvement of 0.17 m/s. Both walking endurance (6MWT) and walkingspeed (10-Meter Walk Test) remained statistically significant after the Bonferroni correction (p<0.0167).
Since the Neuro-QoL overall scores were shown to improve from the baseline to eight-week assessments, we conducted posthoc analyses on the individual Neuro-QoL domain scores. See Table 4 for the changes from baseline to eight-week assessments in individual Neuro-QoL domain scores. While none of the domains were statistically significant, six of the seven domains demonstrated improvement. Anxiety was the only domain that did not show improvement.
While a correlation between HRQOL and functional gait has not been previously determined in DPN populations, researchers have shown that mobility is strongly correlated with HRQOL in older adults and suggest that interventions aimed at limitations to mobility may offer improvements in overall QoL. Assessment of walking speed has been labeled as the “sixth vital sign”, meaning it has the potential to be a primary indicator of function and health status within aging and diseased populations[ 30]. With the knowledge that functional gait is such an important determinant of health, it would be understandable that functional gait might influence HRQOL. While our results only demonstrated a fair correlation between functional gait and HRQOL, these results suggest that a link between functional gait and HRQOL may exist and should be further examined in DPN populations. Perhaps a stronger correlation would be detected with a larger sample size or different QoL assessment.
To our knowledge, this is the first study to assess the effect of yoga on DPN. Overall, we found positive changes in HRQOL, walking speed, and walking endurance. Research by Benbow et al. (1998), established that QoL was significantly more compromised in individuals with DPN than in individuals with diabetes alone . They found that individuals with DPN specifically had more impairments in emotional reactions, energy, pain, physical mobility, and sleep. These findings helped us determine the test domains of the Neuro-QoL that would be appropriate to include the participants in our study. The domains we chose looked at similar aspects of QoL that Benbow et al. (1998) had determined as being impaired in individuals with DPN. We found improvements in all assessed domains of the Neuro-QoL except anxiety. These general trends toward improvement, while not significant, point to the promising effects that yoga may have on the adverse effects of DPN on HRQOL, though this relationship must be further examined.
While no studies have looked at the effects of yoga on DPN, limited research has looked at the effects of exercise interventions on DPN. One intervention that has been looked at for DPN is Tai Chi, a practice with some similarities to yoga. Tai Chi is also grounded in slow intentional movements, often coordinated with breathing and mental imagery. Li & Manor (2010) looked at individuals with peripheral neuropathy (not specific to diabetes) and found that Tai Chi significantly improved individuals’ walking endurance, as measured by the 6MWT. Similarly, we found that individuals’ performance on the 6MWT after eight weeks of yoga improved significantly. In older adult populations, an improvement of 54 meters (177.17 feet) has been demonstrated to be a substantial meaningful change, while an improvement of 20 meters (65.62 feet) has been shown to be a small but meaningful change in the 6MWT. On average, our participants improved by 148.7 feet, more than doubling the 65.62 feet needed to demonstrate a small meaningful change. In addition to finding improvements in walking endurance, our study also demonstrated improvements in walking speed after eight weeks of yoga. In older adult populations, a substantial meaningful change in the 10-Meter Walk Test has been demonstrated to be an improvement of 0.10 m/s or better. Therefore, our change in m/s for the 10-Meter Walk Test after eight weeks of yoga was 0.17, thus far exceeding the criteria for a substantial meaningful change.
Understanding that gait is such an important determinant of health, it is extremely promising to see that participants’ walking speed and walking endurance both significantly improved after engaging in eight weeks of yoga. Noting the fair correlation that we found between functional gait and HRQOL, it is also encouraging to see that six of the seven domains tested for HRQOL using the Neuro-QoL showed improvement after participating in yoga. While the improvements on the Neuro-QoL were not statistically significant, a study with more people could likely demonstrate results that are statically significant. The results of our study demonstrate early support that yoga can offer individuals with DPN improvements in both physical and mental capacities, and warrants further investigation.
Several limitations must be acknowledged in this study. First, this was a relatively small pilot study; therefore we cannot generalize the findings of this study to the DPN population at large. Second, no control group was included; any future study should include a wait-list or randomized control trial design. Thirdly, participants missed sessions and had variable attendance, which may have affected results. One yoga class had to be completely canceled due to weather. Other classes were missed by individual participants due to doctors’ appointments, co-morbidities, travel, family emergencies, and personal conflicts. Lastly, as there was only one group and everyone received yoga, the study was unblinded and the assessors were involved with the yoga intervention. Still, even with these acknowledged limitations, this study demonstrates that yoga may have positive benefits for individuals with DPN.
We conclude that yoga is a potential intervention to promote positive improvements in HRQOL and functional gait, including both walking speed and walking endurance, in individuals with DPN. While our results are only preliminary, they provide a hopeful basis by which further research on yoga should be conducted with this population. Rehabilitation and medical professionals may consider this as a modality for helping individuals manage their DPN.
This project was supported by the Colorado State University, College of Health and Human Sciences Mini-grant pilot funding mechanism. Additional assistance and support were provided for the yoga sessions and assessments by Dave Colangelo, Ruby Bolster, Katie Hinsey, and Carol Chop, RYT, OTR.
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