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The relationship between psychological distress and free-living physical activity in individuals with chronic low back pain
Manual Therapy 15 (2010) 185–189
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Manual Therapy journal homepage: www.elsevier.com/math
Original Article
The relationship between psychological distress and free-living physical activity in individuals with chronic low back pain Cormac G. Ryan*, Heather G. Gray, Mary Newton, Malcolm H. Granat School of Health, Glasgow Caledonian University, G4 0BA, Scotland, UK
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 July 2009 Received in revised form 12 October 2009 Accepted 19 October 2009
The aim of this cross-sectional pilot-study was to investigate the relationship between psychological distress and free-living physical activity (PA) in individuals with chronic low back pain (CLBP). Thirtyeight participants with non-specific CLBP (29 ¼ distressed; 9 ¼ non-distressed) were recruited. PA levels were measured using an accelerometer (activPALÔ activity monitor) over a one week period. The following parameters of physical activity were recorded: time upright (standing or walking), time standing, time walking, and step count. Psychological distress was assessed using a modified version of the distress risk assessment method (DRAM) which is a combination of somatic anxiety and depressive symptoms. The Distressed group spent significantly less time upright over a mean 24 h day (1.47 h, 95% CI 2.70 to 0.23 h, p < 0.05), attributable to 1.01 h less standing and 0.46 h less walking. Depressive symptoms were a statistically significant independent predictor of time upright (b ¼ 0.49, p < 0.05). This pilot-study found that individuals with CLBP and elevated levels of distress spend less time upright than their non-distressed counterparts. Clinically, when treating individuals with CLBP and elevated distress levels, free-living PA may be low and interventions aimed at increasing upright activity may be appropriate. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: Chronic low back pain Psychological distress Physical activity
1. Introduction Psychological distress is a term used to represent a composite of depressive symptoms and somatic anxiety (Main et al., 1992). Levels of psychological distress in people with back pain are relatively high ranging from 13 to 53% (Main et al., 1992; Cairns et al., 2003). Psychological distress is associated with the transition from acute to chronic low back pain (CLBP) (Pincus et al., 2002) and patients with CLBP who have elevated levels of psychological distress have been shown to have an increased relative risk of a poor treatment outcome by three to four times (Cairns et al., 2003). The reasons for this are unclear. Free-living physical activity (PA) can be defined as a person’s everyday physical activity in their usual environment. There is some evidence that patients with CLBP who have elevated levels of depressive symptoms have lower levels of free-living PA than patients with CLBP who do not have elevated levels of depressive symptoms (Keefe et al., 1986; Kerns and Haythornthwaite, 1988; Haythornthwaite et al., 1991). Considering the negative impact associated with disuse (Bortz, 1984) and the positive effects of
* Corresponding author. Tel.: þ44 (0)141 331 3327; fax: þ44 (0)141 331 8112. E-mail address: [email protected] (C.G. Ryan). 1356-689X/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.math.2009.10.007
exercise therapy (Hayden et al., 2005) for this patient group, it could be postulated that the lower levels of free-living PA in patients with CLBP and depressive symptoms could be a contributing factor to poorer clinical outcomes. Previous studies which have compared the levels of free-living PA between patients with CLBP with depressive symptoms compared to those without depressive symptoms have used selfreport methods of measuring free-living PA (Keefe et al., 1986; Kerns and Haythornthwaite, 1988; Haythornthwaite et al., 1991). Self-report methods of measuring free-living PA in individuals with CLBP have been shown to be inaccurate (Kremer et al., 1981; Sanders, 1983; White and Strong, 1992). White and Strong (1992) found that patients with back pain under report their average daily upright time by w1 h. Sanders (1983) found that individuals with CLBP under report significantly more than healthy individuals and other patient groups (Sanders, 1983). Additionally there is evidence to suggest that patients with CBLP may report decreases in their physical activity when it has been observed to increase by an independent observer (Kremer et al., 1981). Thus there is a need to investigate the effects of psychological distress on free-living PA levels in people with CLBP using an objective measure of free-living PA. Such information may provide insight into the role of psychological distress in the development and maintenance of CLBP and direct future physiotherapy management strategies.
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The primary aim of this pilot-study was to quantify and compare the free-living PA levels of individuals with CLBP who have elevated levels of psychological distress to individuals with CLBP who do not have elevated levels of psychological distress. 2. Methods This study used baseline data from a randomised controlled trial (RCT) looking at the affects of exercise and education for people with CLBP. Each participant received a full physiotherapy assessment and completed a set of questionnaires to investigate pain, function, psychological distress, fear of movement and pain selfefficacy. Participants were then provided with a physical activity monitor and asked to wear the monitor for a one week period. The participants were separated into two subgroups based upon their levels of psychological distress. Free-living PA levels were compared between the distressed group and the non-distressed group. 2.1. Participants Participants were recruited from five different National Health Service (NHS) physiotherapy out-patient departments in Glasgow, Scotland. All patients who met the inclusion and exclusion criteria were provided with the opportunity to participate in the study. Other patients who may have noticed the advertisement posters and information leaflets in the waiting room of the physiotherapy departments, and met the inclusion and exclusion criteria, were also allowed to take part. The inclusion criteria were as follows: Between the ages of 18–65 years old; non-specific low back pain for greater than three months duration; No history of low back surgery; the ability to travel independently to hospital/health centre; able and willing to participate in six exercise sessions over a six week period (a requirement of the RCT, within which this study was nested); the ability to read and write English. The exclusion criteria were as follows: physiotherapy within past three months; constant or persistent pain judged on clinical grounds to be due to nerve root irritation; spinal infection, fractures, spondylolithesis or malignancy; women who are or have been pregnant in the past year; a positive response to red flag questions indicating a more serious pathology such as malignancy. Participants were provided with a study information sheet which they read together with the researcher at least once to ensure clarity of what was involved. Prior to commencing the study all participants provided written informed consent. This study received ethical approval from the Greater Glasgow NHS research and ethics committee. 2.2. Outcome measures A modified version of the Distress and Risk Assessment Method (DRAM) was used to assess psychological distress levels (Main et al., 1992). The DRAM combines two questionnaires, the Modified Zung Depression Index (MZDI) (Main and Waddell, 1984) and the Modified Somatic Perception Questionnaire (MSPQ) (Main, 1983). The former is a method of assessing depressive symptoms (0–69 scale) while the later is a method of assessing somatic anxiety sometimes referred to as somatisation (0–39 scale) (Main et al., 1992). From the combined scores of the MZDI and the MSPQ an individual can be classified as either Distressed or Non-distressed. The Non-Distressed group had a MZDI score <17, while the Distressed group had either a MZDI 17 and/or a MSPQ 12 (Bulthuis et al., 2004). Pain levels were assessed using a numerical rating scale (NRS) 0–100 scale. The pain NRS has been shown to be a valid measure of pain sensation assessment demonstrating convergent validity
(r ¼ 0.65–0.88, p < 0.001) with other pain assessment tools (Von Korff et al., 2000). The Tampa Scale of Kinesiophobia-13 (TSK-13) (Goubert et al., 2004) was used to assess kinesiophobia or fear of movement (Kori et al., 1990). The TSK scale consists of 13 items on a four point scale (1 [strongly disagree] – 4 [strongly agree]). The total questionnaire score ranged from 13 to 52, with higher scores indicating greater levels of fear (Geisser et al., 2000; Goubert et al., 2004). The TSK-13 has demonstrated a good level of internal consistency in a CLBP population (Cronbach’s alpha 0.80) (Goubert et al., 2004). The Pain Self efficacy Questionnaire (PSEQ) (Nicholas, 1989) was used to measure an individual’s belief that they can carry out various activities and functions despite their pain (Nicholas et al., 1992). The questionnaire contains 10 items where participants are asked to rate how confident they are that they can perform a certain task or activity. Each item has a 7 point scale from 0 (not at all confident) to 6 (highly confident). The total score can range from 0 to 60, the higher the score the greater the individuals pain selfefficacy. The questionnaire has demonstrated a high level of internal consistency (Cronbach’s alpha ¼ 0.92) and a test–retest reliability of r ¼ 0.73 (p < 0.01), in a group of people with CLBP (Nicholas, 2007). The Roland Morris Disability Questionnaire (RMDQ) was used to measure function. It contains 24 ‘‘yes’’ or ‘‘no’’ questions and is scaled from 0 to 24 with zero representing no disability and 24 indicating severe disability. The RMDQ has demonstrated evidence of content and convergent validity, reliability, and responsiveness to change (Stratford et al., 1996; Roland and Fairbank, 2000; Peat, 2004; Grotle et al., 2005). Free-living PA was assessed using the activPALÔ physical activity monitor (PAL Technologies Ltd, Glasgow, Scotland), a small, single unit, uni-axial accelerometer. This activity monitor has previously been validated for healthy participants (Grant et al., 2006; Ryan et al., 2006; Godfrey et al., 2007) and participants with CLBP (Ryan et al., 2008). The monitor attaches via a double sided adhesive (PalstickiesÔ) to the midline of the mid-thigh. The following parameters of free-living PA were measured: time upright (standing/walking), time standing, time walking and step count. Free-living PA was calculated for a mean day based upon one week of monitoring. The monitor was worn 24 h a day. Only to be removed for water based activities such as bathing as the monitor is not waterproof. Participants were advised to use a new adhesive whenever they reattached the monitor. In an attempt to control employment related activity levels, free-living PA was also calculated for a mean working day and a mean non-working day. A working day was defined as a day where paid work occurred for those who were employed. For those who were not employed a working day was defined as a week day (e.g. Monday to Friday). A non-working day was defined as a day where no paid work occurred for those who were employed or a week end day for those who were not employed (e.g. Saturday or Sunday). 2.3. Data analysis Parametric data are reported as mean SD. Non-parametric data are reported as median inter quartile range (IQR). Unpaired t-tests were used to test possible differences in parametric variables between the Distressed and Non-Distressed groups. Chi square tests were used to compare nominal data between groups, whilst Mann-Whitney U tests were used to compare ordinal data. A multiple regression analysis was then performed to explore the relationship between free-living PA and the different psychosocial variables measured including depressive symptoms, somatisation, pain, function, fear of movement and pain self-efficacy. A p-value of 0.05 was considered statistically significant. All statistical analysis
C.G. Ryan et al. / Manual Therapy 15 (2010) 185–189
was performed using the statistical package SPSS (SPSS inc. USA, version 14.0 for windows) with the exception of post-hoc power calculations which were performed using the statistical package G*Power (Version 3.1.0), a freely available package written by Franz Fauli of Universitat Kiel, Germany (Faul et al., 2007). 3. Results The descriptive characteristics of both groups are shown in Table 1. There was no statistically significant difference between the Distressed and Non-distressed group for any of the descriptive characteristics, however there was a lower percentage of people employed in the Distressed group (69 vs. 33%, p ¼ 0.07). The psychosocial characteristics of both groups are shown in Table 2. The Distressed group reported lower levels of function (p < 0.01), higher levels of fear of movement (p ¼ 0.07) and lower levels of pain self-efficacy (p ¼ 0.07) than the distress group. The Distressed group also demonstrated higher levels of somatic anxiety (MSPQ, p < 0.01) and depressive symptoms (MZDI, p < 0.01). This was to be expected as the classification of distressed/ non-distressed is based upon the scores of the latter two measures. All physical activity data was normally distributed. Due to a combination of technical failures and human error, where the monitor was removed prematurely or forgotten to be worn, a full seven days of recording was not collected for all participants. On average 6.4 days of free living data was collected with a minimum of three and a maximum of seven days recorded. The free-living PA levels of both groups, over a mean day, a mean working day and a mean non-working day, for the four free-living PA parameters are shown in Table 3. Over a mean day, the Distressed group spent significantly less time upright (4.40 vs. 5.87 h, p 0.05), this equated to approximately one and a half hours less time upright. When upright time was broken down into time standing and walking, the distressed group spent approximately one hour less time standing and 30 min less time walking. Over a mean working day, there was no statistically significant difference between groups, although all activity parameters indicated a trend towards lower PA levels in the distressed group. Over a mean nonworking day the Distressed group spent just under one and a half hours less time upright (4.17 vs. 5.61, p < 0.05), one hour less time standing and 24 min less time walking. There was no statistically significant difference in step count between groups over any time period measured. However there was a tendency for fewer steps to be taken in the Distressed group (Table 3). Multiple regression analysis found that the psychosocial variables measured could significantly predict upright time F(6, 31) ¼ 2.385; p 0.05 with an adjusted r2 value of 0.18 during a mean day. However, depressive symptoms (MZDI) was the only statistically significant predictor of upright time (Table 4). According to the regression model, Upright time decreased by approximately w 0.5 h/day for every one standard deviation increase in depressive symptoms. Table 1 Descriptive characteristics.
Gender (females) Employed (no.) Age (yrs) Height (m) Weight (kg) BMI (kg/m2) Pain Duration (yrs)
Non-Distressed Distressed (n ¼ 29) (n ¼ 9)
Mean diff (95% CI)
19 20 45 (12) 1.69 (0.11) 77.81 (12.70) 27.19 (3.75) 9.80 (9.57)
0.64 0.07 1 (7 to 10) 0.78 0.00 (0.09 to 0.09) 0.99 2.55 (7.62 to 12.72) 0.61 1.42 (4.49 to 7.33) 0.60 2.98 (4.06 to 10.02) 0.40
6 3 46 (7) 1.69 (0.12) 80.36 (14.60) 28.61 (7.58) 12.78 (7.26)
p-value
Parametric data are presented as Mean (SD) and non-parametric data are presented as median (IQR).
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Table 2 Psychosocial characteristics.
RMDQ (0–24) TSK-13 (13–52) PSEQ (0–60) MSPQ (0–39) MZDI (0–69) Pain NRS (0–100)
Non-Distressed (n ¼ 29)
Distressed (n ¼ 9)
U-value
p-value
9.0 25.0 51.0 4.0 16.0 30.0
15.0 33.0 42.0 8.0 35.0 60.0
60.0 77.5 77.5 56.0 <0.001 84.5
0.01** 0.07 0.07 0.01** 0.01** 0.12
(6.5) (10.5) (14.5) (5.0) (16.0) (28.5)
(3.0) (13.5) (26.5) (9) (1.5) (54.5)
**Significant difference between the Non-distressed and the Distressed group at p 0.01. Data are presented as median (IQR).
4. Discussion This pilot-study found that individuals with CLBP who have elevated levels of psychological distress have lower levels of freeliving PA than those with CLBP who do not have elevated levels of psychological distress. The distressed group spent one hour and thirty minutes less time upright on a mean day than the non-distressed group. Level of Depressive symptoms was the only psychosocial variable measured which was a statistically significant independent predictor of time upright. The findings of this pilot-study reinforce previous findings which have shown that people with CLBP and depressive symptoms have lower levels of free-living PA than people with CLBP and no depressive symptoms using self-report questionnaires as the method of freeliving PA measurement (Keefe et al., 1986; Kerns and Haythornthwaite, 1988; Haythornthwaite et al., 1991). Self-report methods of measuring free-living PA in individuals with CLBP have been shown to be relatively inaccurate (Kremer et al., 1981; Sanders, 1983; White and Strong, 1992). The current study adds to the literature by reinforcing these early findings using an objective measure of free-living PA. Additionally, the current study quantifies the difference in PA levels. The descriptive characteristics showed that more people in the distressed group were unemployed compared to the non-distressed group. There is evidence to show that employment status and type of occupation can affect a person’s level of free-living PA (Sallis et al., 1985; Philippaerts and Lefevre, 1998). To factor out the effect of occupation on free-living PA levels between groups the weeks PA was sub divided into working days (week days for the unemployed participants) and non-working days (weekend days for the unemployed participants). Time spent upright was statistically lower during a mean non-working day but not during a mean working day. The reason for this difference between a mean working day and a mean non-working day cannot be explained by the data collected. However it could be hypothesised that during a working day, there are a set of chores and tasks which need to be achieved, such as travelling to the place of work, and for these tasks to be achieved a certain level of upright activity is required. During a non-working day activities are less ‘‘constrained’’ by the external or societal requirements of employment or work and so individuals are free to behave as they wish to do. Without the external requirements or constraints of having to go to work/employment the distressed group may be more likely to choose to be less active. Irrespective of the rationale for why the difference between groups was greater on a mean non-working day, this finding highlights that the difference between groups was not simply attributable to employment status. The psychosocial characteristics of both groups show that participants in the distressed group had higher levels of pain, fear of movement and lower levels of function and pain self-efficacy. A multiple regression was performed to see which psychosocial factors were significant independent predictors of time upright. Only depressive symptoms, measured using the MZDI, was a significant
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Table 3 Free-living PA levels. Non-Distressed (n ¼ 28)
Distressed (n ¼ 9)
95% CI
p-value
Mean day Time Upright (hrs/day) Time Standing (hrs/day) Time Walking (hrs/day) Step count (no.)
5.87 3.58 2.29 8,613
(1.72) (1.19) (0.69) (2,971)
4.40 2.57 1.83 6,937
(1.08) (0.62) (0.57) (2,905)
2.70 to 0.23 1.87 to 0.17 0.97 to 0.06 3,964 to 611
0.05* 0.01a,** 0.08 0.15
Mean Working day Time Upright (hrs/day) Time Standing (hrs/day Time Walking (hrs/day) Step count (no.)
6.00 3.65 2.35 8,945
(1.97) (1.37) (0.75) (3110)
4.85 2.96 1.89 7,224
(1.78) (1.32) (0.66) (3336)
2.65 to 0.35 1.76 to 0.36 1.02 to 0.11 4,181 to 740
Mean Non-Working day Time Upright (hrs/day) Time Standing (hrs/day Time Walking (hrs/day) Step count (no.)
5.61 3.43 2.18 8,069
(1.95) (1.31) (0.82) (3, 476)
4.17 2.39 1.78 6,720
(0.83) (0.41) (0.59) (2,717)
2.81 to 0.06 1.94 to 0.12 1.01 to 0.20 3,942 to 1,242
0.13 0.19 0.11 0.17
0.05* 0.05* 0.18 0.30
*Significant difference between the Distressed and non-distressed group at p 0.05. **Significant difference between the Distressed and non-distressed group at p 0.01. Data are presented as mean (SD). One individual in the Non-distressed group was monitored over three non-working week days only, thus only 28 participants were in the Nondistressed group for this comparison. a Equal variances not assumed.
independent predictor of time upright during a mean day (b ¼ 0.49, p < 0.05). This finding supports previous literature that pain levels have no effect on free-living PA levels in people with CLBP (LiszkaHackzell and Martin, 2004). Considering the premise of the fear avoidance model of musculoskeletal pain (Vlaeyen et al.,1995; Leeuw et al., 2007) it was somewhat surprising that fear of movement was not a significant predictor of free-living PA, although it may be that fear of movement mediates an effect on PA through increased depressive symptoms. The findings of this study support those of a longitudinal study which found that change in free-living PA from the stage of acute low back pain to CLBP, one year later, was associated with depressive symptoms (measured using the Beck Depression Inventory) and not fear of movement (Bousema et al., 2007). Lower PA levels may provide some insight into why individuals with CLBP and elevated distress have poorer outcomes than their non-distressed counterparts (Main et al., 1992; Cairns et al., 2003). Clinically, when dealing with distressed patients with CLBP freeliving PA levels may be a factor that needs to be addressed, and may be of more importance than when dealing with non-distressed CLBP patients. Objectively monitoring free-living PA levels could be used to assess if activity levels are low and assist in the planning and monitoring of individualised programmes targeted at gradually increasing free-living PA (Protas, 1999; Ryan et al., 2008). If successful in elevating free-living PA there could be positive effects on psychological distress which could in turn lead to improved outcomes for this challenging patient group. A purpose of this pilot-study was to provide sufficient information to estimate the required sample size for a full scale
Table 4 Multiple regression analysis of predictors of time upright.
Constant RMDQ TSK-13 PSEQ MSPQ MZDI Pain NRS
5. Conclusions
Unstandardised coefficients
Standardised coefficients
B
Std. Error
Beta
5.68 0.06 0.02 0.02 0.03 0.07 0.01
2.78 0.07 0.04 0.03 0.07 0.03 0.01
0.17 0.10 0.15 0.8 0.49 0.15
*Significant at p 0.05.
appropriately powered trial. Time spent upright, which was the primary outcome measure, was found to be statistically significant using the sample size involved in the pilot-study with an effect size of 1.02. The two free-living physical activity parameters which did not reach statistical significance were time spent walking and step count. For time spent walking a sample size of 82 individuals (61 ¼ Non-Distressed and 21 ¼ Distressed) would be required to detect an effect size of 0.72 with 80% power. For step count a sample size of 132 individuals (99 ¼ Non-Distressed and 33 ¼ Distressed) would be required to detect an effect size of 0.57 with 80% power. Considering the magnitude of the effect size and the clinical relevance of the difference in free-living PA between groups a full scale trial is warranted. A limitation of this study was its small and unbalanced sample size which increased the risk of making type II errors. This means that real differences and relationships which existed within the data may not have achieved statistical significance due to a lack of statistical power. For example, the difference in step count between groups may have been statistically significant had a larger sample been used. However, the purpose of this pilot-study was to provide data for a power calculation so that an appropriately powered study can be carried out in the future. The cross-sectional nature of this study means that a causal relationship between psychological distress and free-living PA in people with CLBP cannot be explored. Future studies should further investigate the relationship between free-living PA and psychological distress using longitudinal designs. A strength of this study was that many of the factors which may have impacted upon free-living PA measurement were similar between groups such as age, gender and BMI.
p-value
0.05 0.40 0.62 0.54 0.68 0.05* 0.41
In conclusion, our pilot-data show that individuals with CLBP and elevated levels of psychological distress have lower levels of free-living PA than non-distressed individuals with CLBP. The magnitude of this difference appeared to be relatively large, the distressed participants spending approximately one hour and thirty minutes less time upright during the day compared to their non-distressed counterparts. The difference between groups was greatest during non-working days suggesting that employment status did not account for differences in free-living PA. Furthermore depressive symptoms were an independent predictor of free-living
C.G. Ryan et al. / Manual Therapy 15 (2010) 185–189
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Manual Therapy journal homepage: www.elsevier.com/math
Original Article
The relationship between psychological distress and free-living physical activity in individuals with chronic low back pain Cormac G. Ryan*, Heather G. Gray, Mary Newton, Malcolm H. Granat School of Health, Glasgow Caledonian University, G4 0BA, Scotland, UK
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 July 2009 Received in revised form 12 October 2009 Accepted 19 October 2009
The aim of this cross-sectional pilot-study was to investigate the relationship between psychological distress and free-living physical activity (PA) in individuals with chronic low back pain (CLBP). Thirtyeight participants with non-specific CLBP (29 ¼ distressed; 9 ¼ non-distressed) were recruited. PA levels were measured using an accelerometer (activPALÔ activity monitor) over a one week period. The following parameters of physical activity were recorded: time upright (standing or walking), time standing, time walking, and step count. Psychological distress was assessed using a modified version of the distress risk assessment method (DRAM) which is a combination of somatic anxiety and depressive symptoms. The Distressed group spent significantly less time upright over a mean 24 h day (1.47 h, 95% CI 2.70 to 0.23 h, p < 0.05), attributable to 1.01 h less standing and 0.46 h less walking. Depressive symptoms were a statistically significant independent predictor of time upright (b ¼ 0.49, p < 0.05). This pilot-study found that individuals with CLBP and elevated levels of distress spend less time upright than their non-distressed counterparts. Clinically, when treating individuals with CLBP and elevated distress levels, free-living PA may be low and interventions aimed at increasing upright activity may be appropriate. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: Chronic low back pain Psychological distress Physical activity
1. Introduction Psychological distress is a term used to represent a composite of depressive symptoms and somatic anxiety (Main et al., 1992). Levels of psychological distress in people with back pain are relatively high ranging from 13 to 53% (Main et al., 1992; Cairns et al., 2003). Psychological distress is associated with the transition from acute to chronic low back pain (CLBP) (Pincus et al., 2002) and patients with CLBP who have elevated levels of psychological distress have been shown to have an increased relative risk of a poor treatment outcome by three to four times (Cairns et al., 2003). The reasons for this are unclear. Free-living physical activity (PA) can be defined as a person’s everyday physical activity in their usual environment. There is some evidence that patients with CLBP who have elevated levels of depressive symptoms have lower levels of free-living PA than patients with CLBP who do not have elevated levels of depressive symptoms (Keefe et al., 1986; Kerns and Haythornthwaite, 1988; Haythornthwaite et al., 1991). Considering the negative impact associated with disuse (Bortz, 1984) and the positive effects of
* Corresponding author. Tel.: þ44 (0)141 331 3327; fax: þ44 (0)141 331 8112. E-mail address: [email protected] (C.G. Ryan). 1356-689X/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.math.2009.10.007
exercise therapy (Hayden et al., 2005) for this patient group, it could be postulated that the lower levels of free-living PA in patients with CLBP and depressive symptoms could be a contributing factor to poorer clinical outcomes. Previous studies which have compared the levels of free-living PA between patients with CLBP with depressive symptoms compared to those without depressive symptoms have used selfreport methods of measuring free-living PA (Keefe et al., 1986; Kerns and Haythornthwaite, 1988; Haythornthwaite et al., 1991). Self-report methods of measuring free-living PA in individuals with CLBP have been shown to be inaccurate (Kremer et al., 1981; Sanders, 1983; White and Strong, 1992). White and Strong (1992) found that patients with back pain under report their average daily upright time by w1 h. Sanders (1983) found that individuals with CLBP under report significantly more than healthy individuals and other patient groups (Sanders, 1983). Additionally there is evidence to suggest that patients with CBLP may report decreases in their physical activity when it has been observed to increase by an independent observer (Kremer et al., 1981). Thus there is a need to investigate the effects of psychological distress on free-living PA levels in people with CLBP using an objective measure of free-living PA. Such information may provide insight into the role of psychological distress in the development and maintenance of CLBP and direct future physiotherapy management strategies.
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The primary aim of this pilot-study was to quantify and compare the free-living PA levels of individuals with CLBP who have elevated levels of psychological distress to individuals with CLBP who do not have elevated levels of psychological distress. 2. Methods This study used baseline data from a randomised controlled trial (RCT) looking at the affects of exercise and education for people with CLBP. Each participant received a full physiotherapy assessment and completed a set of questionnaires to investigate pain, function, psychological distress, fear of movement and pain selfefficacy. Participants were then provided with a physical activity monitor and asked to wear the monitor for a one week period. The participants were separated into two subgroups based upon their levels of psychological distress. Free-living PA levels were compared between the distressed group and the non-distressed group. 2.1. Participants Participants were recruited from five different National Health Service (NHS) physiotherapy out-patient departments in Glasgow, Scotland. All patients who met the inclusion and exclusion criteria were provided with the opportunity to participate in the study. Other patients who may have noticed the advertisement posters and information leaflets in the waiting room of the physiotherapy departments, and met the inclusion and exclusion criteria, were also allowed to take part. The inclusion criteria were as follows: Between the ages of 18–65 years old; non-specific low back pain for greater than three months duration; No history of low back surgery; the ability to travel independently to hospital/health centre; able and willing to participate in six exercise sessions over a six week period (a requirement of the RCT, within which this study was nested); the ability to read and write English. The exclusion criteria were as follows: physiotherapy within past three months; constant or persistent pain judged on clinical grounds to be due to nerve root irritation; spinal infection, fractures, spondylolithesis or malignancy; women who are or have been pregnant in the past year; a positive response to red flag questions indicating a more serious pathology such as malignancy. Participants were provided with a study information sheet which they read together with the researcher at least once to ensure clarity of what was involved. Prior to commencing the study all participants provided written informed consent. This study received ethical approval from the Greater Glasgow NHS research and ethics committee. 2.2. Outcome measures A modified version of the Distress and Risk Assessment Method (DRAM) was used to assess psychological distress levels (Main et al., 1992). The DRAM combines two questionnaires, the Modified Zung Depression Index (MZDI) (Main and Waddell, 1984) and the Modified Somatic Perception Questionnaire (MSPQ) (Main, 1983). The former is a method of assessing depressive symptoms (0–69 scale) while the later is a method of assessing somatic anxiety sometimes referred to as somatisation (0–39 scale) (Main et al., 1992). From the combined scores of the MZDI and the MSPQ an individual can be classified as either Distressed or Non-distressed. The Non-Distressed group had a MZDI score <17, while the Distressed group had either a MZDI 17 and/or a MSPQ 12 (Bulthuis et al., 2004). Pain levels were assessed using a numerical rating scale (NRS) 0–100 scale. The pain NRS has been shown to be a valid measure of pain sensation assessment demonstrating convergent validity
(r ¼ 0.65–0.88, p < 0.001) with other pain assessment tools (Von Korff et al., 2000). The Tampa Scale of Kinesiophobia-13 (TSK-13) (Goubert et al., 2004) was used to assess kinesiophobia or fear of movement (Kori et al., 1990). The TSK scale consists of 13 items on a four point scale (1 [strongly disagree] – 4 [strongly agree]). The total questionnaire score ranged from 13 to 52, with higher scores indicating greater levels of fear (Geisser et al., 2000; Goubert et al., 2004). The TSK-13 has demonstrated a good level of internal consistency in a CLBP population (Cronbach’s alpha 0.80) (Goubert et al., 2004). The Pain Self efficacy Questionnaire (PSEQ) (Nicholas, 1989) was used to measure an individual’s belief that they can carry out various activities and functions despite their pain (Nicholas et al., 1992). The questionnaire contains 10 items where participants are asked to rate how confident they are that they can perform a certain task or activity. Each item has a 7 point scale from 0 (not at all confident) to 6 (highly confident). The total score can range from 0 to 60, the higher the score the greater the individuals pain selfefficacy. The questionnaire has demonstrated a high level of internal consistency (Cronbach’s alpha ¼ 0.92) and a test–retest reliability of r ¼ 0.73 (p < 0.01), in a group of people with CLBP (Nicholas, 2007). The Roland Morris Disability Questionnaire (RMDQ) was used to measure function. It contains 24 ‘‘yes’’ or ‘‘no’’ questions and is scaled from 0 to 24 with zero representing no disability and 24 indicating severe disability. The RMDQ has demonstrated evidence of content and convergent validity, reliability, and responsiveness to change (Stratford et al., 1996; Roland and Fairbank, 2000; Peat, 2004; Grotle et al., 2005). Free-living PA was assessed using the activPALÔ physical activity monitor (PAL Technologies Ltd, Glasgow, Scotland), a small, single unit, uni-axial accelerometer. This activity monitor has previously been validated for healthy participants (Grant et al., 2006; Ryan et al., 2006; Godfrey et al., 2007) and participants with CLBP (Ryan et al., 2008). The monitor attaches via a double sided adhesive (PalstickiesÔ) to the midline of the mid-thigh. The following parameters of free-living PA were measured: time upright (standing/walking), time standing, time walking and step count. Free-living PA was calculated for a mean day based upon one week of monitoring. The monitor was worn 24 h a day. Only to be removed for water based activities such as bathing as the monitor is not waterproof. Participants were advised to use a new adhesive whenever they reattached the monitor. In an attempt to control employment related activity levels, free-living PA was also calculated for a mean working day and a mean non-working day. A working day was defined as a day where paid work occurred for those who were employed. For those who were not employed a working day was defined as a week day (e.g. Monday to Friday). A non-working day was defined as a day where no paid work occurred for those who were employed or a week end day for those who were not employed (e.g. Saturday or Sunday). 2.3. Data analysis Parametric data are reported as mean SD. Non-parametric data are reported as median inter quartile range (IQR). Unpaired t-tests were used to test possible differences in parametric variables between the Distressed and Non-Distressed groups. Chi square tests were used to compare nominal data between groups, whilst Mann-Whitney U tests were used to compare ordinal data. A multiple regression analysis was then performed to explore the relationship between free-living PA and the different psychosocial variables measured including depressive symptoms, somatisation, pain, function, fear of movement and pain self-efficacy. A p-value of 0.05 was considered statistically significant. All statistical analysis
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was performed using the statistical package SPSS (SPSS inc. USA, version 14.0 for windows) with the exception of post-hoc power calculations which were performed using the statistical package G*Power (Version 3.1.0), a freely available package written by Franz Fauli of Universitat Kiel, Germany (Faul et al., 2007). 3. Results The descriptive characteristics of both groups are shown in Table 1. There was no statistically significant difference between the Distressed and Non-distressed group for any of the descriptive characteristics, however there was a lower percentage of people employed in the Distressed group (69 vs. 33%, p ¼ 0.07). The psychosocial characteristics of both groups are shown in Table 2. The Distressed group reported lower levels of function (p < 0.01), higher levels of fear of movement (p ¼ 0.07) and lower levels of pain self-efficacy (p ¼ 0.07) than the distress group. The Distressed group also demonstrated higher levels of somatic anxiety (MSPQ, p < 0.01) and depressive symptoms (MZDI, p < 0.01). This was to be expected as the classification of distressed/ non-distressed is based upon the scores of the latter two measures. All physical activity data was normally distributed. Due to a combination of technical failures and human error, where the monitor was removed prematurely or forgotten to be worn, a full seven days of recording was not collected for all participants. On average 6.4 days of free living data was collected with a minimum of three and a maximum of seven days recorded. The free-living PA levels of both groups, over a mean day, a mean working day and a mean non-working day, for the four free-living PA parameters are shown in Table 3. Over a mean day, the Distressed group spent significantly less time upright (4.40 vs. 5.87 h, p 0.05), this equated to approximately one and a half hours less time upright. When upright time was broken down into time standing and walking, the distressed group spent approximately one hour less time standing and 30 min less time walking. Over a mean working day, there was no statistically significant difference between groups, although all activity parameters indicated a trend towards lower PA levels in the distressed group. Over a mean nonworking day the Distressed group spent just under one and a half hours less time upright (4.17 vs. 5.61, p < 0.05), one hour less time standing and 24 min less time walking. There was no statistically significant difference in step count between groups over any time period measured. However there was a tendency for fewer steps to be taken in the Distressed group (Table 3). Multiple regression analysis found that the psychosocial variables measured could significantly predict upright time F(6, 31) ¼ 2.385; p 0.05 with an adjusted r2 value of 0.18 during a mean day. However, depressive symptoms (MZDI) was the only statistically significant predictor of upright time (Table 4). According to the regression model, Upright time decreased by approximately w 0.5 h/day for every one standard deviation increase in depressive symptoms. Table 1 Descriptive characteristics.
Gender (females) Employed (no.) Age (yrs) Height (m) Weight (kg) BMI (kg/m2) Pain Duration (yrs)
Non-Distressed Distressed (n ¼ 29) (n ¼ 9)
Mean diff (95% CI)
19 20 45 (12) 1.69 (0.11) 77.81 (12.70) 27.19 (3.75) 9.80 (9.57)
0.64 0.07 1 (7 to 10) 0.78 0.00 (0.09 to 0.09) 0.99 2.55 (7.62 to 12.72) 0.61 1.42 (4.49 to 7.33) 0.60 2.98 (4.06 to 10.02) 0.40
6 3 46 (7) 1.69 (0.12) 80.36 (14.60) 28.61 (7.58) 12.78 (7.26)
p-value
Parametric data are presented as Mean (SD) and non-parametric data are presented as median (IQR).
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Table 2 Psychosocial characteristics.
RMDQ (0–24) TSK-13 (13–52) PSEQ (0–60) MSPQ (0–39) MZDI (0–69) Pain NRS (0–100)
Non-Distressed (n ¼ 29)
Distressed (n ¼ 9)
U-value
p-value
9.0 25.0 51.0 4.0 16.0 30.0
15.0 33.0 42.0 8.0 35.0 60.0
60.0 77.5 77.5 56.0 <0.001 84.5
0.01** 0.07 0.07 0.01** 0.01** 0.12
(6.5) (10.5) (14.5) (5.0) (16.0) (28.5)
(3.0) (13.5) (26.5) (9) (1.5) (54.5)
**Significant difference between the Non-distressed and the Distressed group at p 0.01. Data are presented as median (IQR).
4. Discussion This pilot-study found that individuals with CLBP who have elevated levels of psychological distress have lower levels of freeliving PA than those with CLBP who do not have elevated levels of psychological distress. The distressed group spent one hour and thirty minutes less time upright on a mean day than the non-distressed group. Level of Depressive symptoms was the only psychosocial variable measured which was a statistically significant independent predictor of time upright. The findings of this pilot-study reinforce previous findings which have shown that people with CLBP and depressive symptoms have lower levels of free-living PA than people with CLBP and no depressive symptoms using self-report questionnaires as the method of freeliving PA measurement (Keefe et al., 1986; Kerns and Haythornthwaite, 1988; Haythornthwaite et al., 1991). Self-report methods of measuring free-living PA in individuals with CLBP have been shown to be relatively inaccurate (Kremer et al., 1981; Sanders, 1983; White and Strong, 1992). The current study adds to the literature by reinforcing these early findings using an objective measure of free-living PA. Additionally, the current study quantifies the difference in PA levels. The descriptive characteristics showed that more people in the distressed group were unemployed compared to the non-distressed group. There is evidence to show that employment status and type of occupation can affect a person’s level of free-living PA (Sallis et al., 1985; Philippaerts and Lefevre, 1998). To factor out the effect of occupation on free-living PA levels between groups the weeks PA was sub divided into working days (week days for the unemployed participants) and non-working days (weekend days for the unemployed participants). Time spent upright was statistically lower during a mean non-working day but not during a mean working day. The reason for this difference between a mean working day and a mean non-working day cannot be explained by the data collected. However it could be hypothesised that during a working day, there are a set of chores and tasks which need to be achieved, such as travelling to the place of work, and for these tasks to be achieved a certain level of upright activity is required. During a non-working day activities are less ‘‘constrained’’ by the external or societal requirements of employment or work and so individuals are free to behave as they wish to do. Without the external requirements or constraints of having to go to work/employment the distressed group may be more likely to choose to be less active. Irrespective of the rationale for why the difference between groups was greater on a mean non-working day, this finding highlights that the difference between groups was not simply attributable to employment status. The psychosocial characteristics of both groups show that participants in the distressed group had higher levels of pain, fear of movement and lower levels of function and pain self-efficacy. A multiple regression was performed to see which psychosocial factors were significant independent predictors of time upright. Only depressive symptoms, measured using the MZDI, was a significant
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Table 3 Free-living PA levels. Non-Distressed (n ¼ 28)
Distressed (n ¼ 9)
95% CI
p-value
Mean day Time Upright (hrs/day) Time Standing (hrs/day) Time Walking (hrs/day) Step count (no.)
5.87 3.58 2.29 8,613
(1.72) (1.19) (0.69) (2,971)
4.40 2.57 1.83 6,937
(1.08) (0.62) (0.57) (2,905)
2.70 to 0.23 1.87 to 0.17 0.97 to 0.06 3,964 to 611
0.05* 0.01a,** 0.08 0.15
Mean Working day Time Upright (hrs/day) Time Standing (hrs/day Time Walking (hrs/day) Step count (no.)
6.00 3.65 2.35 8,945
(1.97) (1.37) (0.75) (3110)
4.85 2.96 1.89 7,224
(1.78) (1.32) (0.66) (3336)
2.65 to 0.35 1.76 to 0.36 1.02 to 0.11 4,181 to 740
Mean Non-Working day Time Upright (hrs/day) Time Standing (hrs/day Time Walking (hrs/day) Step count (no.)
5.61 3.43 2.18 8,069
(1.95) (1.31) (0.82) (3, 476)
4.17 2.39 1.78 6,720
(0.83) (0.41) (0.59) (2,717)
2.81 to 0.06 1.94 to 0.12 1.01 to 0.20 3,942 to 1,242
0.13 0.19 0.11 0.17
0.05* 0.05* 0.18 0.30
*Significant difference between the Distressed and non-distressed group at p 0.05. **Significant difference between the Distressed and non-distressed group at p 0.01. Data are presented as mean (SD). One individual in the Non-distressed group was monitored over three non-working week days only, thus only 28 participants were in the Nondistressed group for this comparison. a Equal variances not assumed.
independent predictor of time upright during a mean day (b ¼ 0.49, p < 0.05). This finding supports previous literature that pain levels have no effect on free-living PA levels in people with CLBP (LiszkaHackzell and Martin, 2004). Considering the premise of the fear avoidance model of musculoskeletal pain (Vlaeyen et al.,1995; Leeuw et al., 2007) it was somewhat surprising that fear of movement was not a significant predictor of free-living PA, although it may be that fear of movement mediates an effect on PA through increased depressive symptoms. The findings of this study support those of a longitudinal study which found that change in free-living PA from the stage of acute low back pain to CLBP, one year later, was associated with depressive symptoms (measured using the Beck Depression Inventory) and not fear of movement (Bousema et al., 2007). Lower PA levels may provide some insight into why individuals with CLBP and elevated distress have poorer outcomes than their non-distressed counterparts (Main et al., 1992; Cairns et al., 2003). Clinically, when dealing with distressed patients with CLBP freeliving PA levels may be a factor that needs to be addressed, and may be of more importance than when dealing with non-distressed CLBP patients. Objectively monitoring free-living PA levels could be used to assess if activity levels are low and assist in the planning and monitoring of individualised programmes targeted at gradually increasing free-living PA (Protas, 1999; Ryan et al., 2008). If successful in elevating free-living PA there could be positive effects on psychological distress which could in turn lead to improved outcomes for this challenging patient group. A purpose of this pilot-study was to provide sufficient information to estimate the required sample size for a full scale
Table 4 Multiple regression analysis of predictors of time upright.
Constant RMDQ TSK-13 PSEQ MSPQ MZDI Pain NRS
5. Conclusions
Unstandardised coefficients
Standardised coefficients
B
Std. Error
Beta
5.68 0.06 0.02 0.02 0.03 0.07 0.01
2.78 0.07 0.04 0.03 0.07 0.03 0.01
0.17 0.10 0.15 0.8 0.49 0.15
*Significant at p 0.05.
appropriately powered trial. Time spent upright, which was the primary outcome measure, was found to be statistically significant using the sample size involved in the pilot-study with an effect size of 1.02. The two free-living physical activity parameters which did not reach statistical significance were time spent walking and step count. For time spent walking a sample size of 82 individuals (61 ¼ Non-Distressed and 21 ¼ Distressed) would be required to detect an effect size of 0.72 with 80% power. For step count a sample size of 132 individuals (99 ¼ Non-Distressed and 33 ¼ Distressed) would be required to detect an effect size of 0.57 with 80% power. Considering the magnitude of the effect size and the clinical relevance of the difference in free-living PA between groups a full scale trial is warranted. A limitation of this study was its small and unbalanced sample size which increased the risk of making type II errors. This means that real differences and relationships which existed within the data may not have achieved statistical significance due to a lack of statistical power. For example, the difference in step count between groups may have been statistically significant had a larger sample been used. However, the purpose of this pilot-study was to provide data for a power calculation so that an appropriately powered study can be carried out in the future. The cross-sectional nature of this study means that a causal relationship between psychological distress and free-living PA in people with CLBP cannot be explored. Future studies should further investigate the relationship between free-living PA and psychological distress using longitudinal designs. A strength of this study was that many of the factors which may have impacted upon free-living PA measurement were similar between groups such as age, gender and BMI.
p-value
0.05 0.40 0.62 0.54 0.68 0.05* 0.41
In conclusion, our pilot-data show that individuals with CLBP and elevated levels of psychological distress have lower levels of free-living PA than non-distressed individuals with CLBP. The magnitude of this difference appeared to be relatively large, the distressed participants spending approximately one hour and thirty minutes less time upright during the day compared to their non-distressed counterparts. The difference between groups was greatest during non-working days suggesting that employment status did not account for differences in free-living PA. Furthermore depressive symptoms were an independent predictor of free-living
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