Of the 542 participants who were recruited for this study, 506 (93.4%) returned the study questionnaire. 463 participants were included in the analyses after excluding 43, as they were considered outliers (as per the IPAQ guidelines) (14). However, there were no differences between the outliers and those included in the final analyses in terms of age, BMI, depression, pain intensity and disability (p = 0.07–0.63), with the exception of a higher percentage of women employed in the outlier group (39 (90.7%) vs. 278 (61.2%), p < 0.001).
The mean (SD) age and BMI of the study cohort was 56.9 (12.7) years and 27.4 (5.6) kg/m2, respectively. A total of 278 (60.3%) participants were employed and 62 (13.4%) self-reported depression. The mean (SD) LBP intensity and disability scores were 25.6 (22.3) and 13.9 (20.5) respectively. The median (interquartile range (IQR)) total physical activity (MET, hours/week) for the cohort was 49.1 (82.1).
The characteristics of participants with no/low and high LBP intensity are presented in Table 2. High intensity back pain was reported in 71 (15.3%) women. Compared to women with no or low intensity back pain, those with high intensity back pain had a greater BMI (mean(SD) = 29.5 (5.3) vs. 27.0 (5.7), p = 0.001), were more likely to be depressed (16 (22.5%) vs. 46 (11.7%), p = 0.01) and less likely to be employed (33 (47.1%) vs. 245 (62.6%), p = 0.02). There were no differences between the pain intensity groups in their physical activity and sitting time, with the exception that fewer women with high pain intensity reported doing physical activity at work (16 (23.5%) vs. 142 (36.6%), p = 0.04).
Table 2
Characteristics of participants with no or low and high levels of low back pain and disability.
| Total cohort (n = 463)a | No/low pain intensity (n = 392) | High pain intensity (n = 71) | P value | No/ low disability (n = 425) | High disability (n = 38) | P value |
Age (years)b | 56.9 (12.7) | 56.7 (12.7) | 57.9 (12.7) | 0.45 | 56.6 (12.8) | 59.9 (11.7) | 0.12 |
Body mass index (kg/m2)b | 27.4 (5.6) | 27.0 (5.7) | 29.5 (5.3) | 0.001 | 27.2 (5.6) | 29.8 (5.7) | 0.01 |
Depression, n (%) | 62 (13.4) | 46 (11.7) | 16 (22.5) | 0.01 | 56 (13.2) | 6 (15.8) | 0.65 |
Working, n (%) | 278 (60.3) | 245 (62.6) | 33 (47.1) | 0.02 | 264 (62.4) | 14 (36.8) | 0.002 |
Physical activity |
Types of physical activity |
Work-related activity |
n (%) | 158 (34.7) | 142 (36.6) | 16 (23.5) | 0.04 | 149 (35.6) | 9 (24.3) | 0.17 |
MET(hours/week)c,d | 1.27 (22.6) | 0 (8.0) | 0 (0) | 0.05 | 0 (9.4) | 0 (0) | 0.05 |
Active transportation |
n (%) | 315 (69.1) | 264 (68.0) | 51 (75.0) | 0.25 | 291 (69.5) | 24 (64.9) | 0.56 |
MET(hours/week ) c,d | 3.3 (11.0) | 3.3 (11.0) | 4.95 (11.3) | 0.22 | 3.3 (11.6) | 1.7 (5.5) | 0.09 |
Domestic and garden activity |
n (%) | 420 (92.1) | 358 (92.3) | 62 (91.2) | 0.76 | 358 (91.9) | 35 (94.6) | 0.56 |
MET(hours/week ) c,d | 18.9 (42.8) | 18.6 (41.3) | 19.1 (60.0) | 0.64 | 19.5 (42.0) | 16.3 (52.5) | 0.70 |
Leisure activity |
n (%) | 311 (68.2) | 268 (69.1) | 43 (63.2) | 0.34 | 294 (70.2) | 17 (45.9) | 0.002 |
MET(hours/week ) c,d | 6.0 (16.5) | 6.0 (16.3) | 5.5 (19.2) | 0.67 | 6.6 (16.6) | 0 (6.6) | 0.003 |
Intensity of physical activity |
Vigorous activity |
n (%) | 137 (30.0) | 120 (30.9) | 17 (25) | 0.33 | 134 (32.0) | 3 (8.11) | 0.002 |
MET(hours/week ) c,d | 0 (8) | 0 (8) | 0 (2) | 0.28 | 0 (8) | 0 (0) | 0.002 |
Moderate activity |
n (%) | 429 (94.1) | 366 (94.3) | 63 (92.7) | 0.59 | 394 (94.0) | 35 (94.6) | 0.89 |
MET(hours/week ) c,d | 27.8 (55) | 27.8 (53.8) | 27.4 (73.8) | 0.71 | 29 (55.0) | 19 (48.8) | 0.30 |
Walking |
n (%) | 396 (86.8) | 336 (86.6) | 60 (88.2) | 0.71 | 366 (87.4) | 30 (81.1) | 0.28 |
MET(hours/week ) c,d | 10.5 (19.8) | 11.0 (19.3) | 8.3 (23.4) | 0.8 | 11.6 (19.8) | 6.6 (11.6) | 0.02 |
Total activity |
n (%) | 455 (99.8) | 387 (99.7) | 68 (100) | 0.68 | 418 (99.8) | 37 (100) | 0.77 |
MET(hours/week ) c,d | 49.1 (82.1) | 49.7 (78.6) | 39.2 (92.6) | 0.97 | 50.6 (82.4) | 26.4 (66.4) | 0.01 |
Sitting time (hours/week) c,d | 35 (24) | 35 (22) | 35 (33) | 0.85 | 35 (24) | 36 (24) | 0.37 |
a Based on the IPAQ guidelines, any participant reporting over 16 hours of physical activity per day or more than 7 days a week for activity should be considered as an outlier, therefore a total of 43 (8.6%) participants were excluded from the analysis; b Mean (standard deviation);cMedian (interquartile range); d MET = metabolic equivalent task. |
Thirty-eight (8.2%) women reported high levels of back disability (Table 2). Compared to women with no or low levels of disability, women with high disability had a higher BMI (mean(SD) = 29.8 (5.7) vs. 27.2 (5.6), p = 0.01) and less likely to be employed (14 (36.8%) vs. 264 (62.4%), p = 0.002). Women with high back disability were also less likely to perform leisure activity (17 (45.9%) vs. 294 (70.2%), p = 0.002) and vigorous activity (3 (8.11%) vs. 134 (32%), p = 0.002), and reported less MET (hours/week) in leisure activity (median (IQR) = 0 (6.6) vs. 6.6 (16.6), p = 0.003), vigorous activity (0 (0) vs. 0 (8), p = 0.002), walking (6.6 (11.6) vs. 11.6 (19.8), p = 0.02) and total physical activity (26.4 (66.4) vs. 50.6 (82.4), p = 0.01). There were no significant differences in active transportation, domestic and gardening activity, moderate activity and sitting time between women with high and no/low disability.
Associations Between Low Back Pain Intensity And Physical Activity
After adjustment for age, BMI and depression (Table 3, model 1), there were no significant differences between women with high levels of LBP intensity and those with no/low LBP intensity in any physical activity (MET, hours/week), including domestic and gardening activities (estimated marginal median (95%CI) = 21.8 (13.2–30.4) vs. 21.4 (17.1–25.6), p = 0.92), walking (11.0 (7.1–15.0) vs. 11.1 (9.4–12.8), p = 0.98), moderate activity (28.8 (18.3–39.4) vs. 31.4 (25.1–37.7), p = 0.67), total physical activity (45.6 (19.0-72.3) vs. 53.2 (45.1–61.3), p = 0.59), or sitting time (hours/week) (33.6 (29.5–38.2) vs. 34.8 (32.9–36.6), p = 0.37). With the addition of adjustment for working status (Table 3, model 2; Fig. 1(A) and (B)), these results remained unchanged.
Table 3
The association between levels of low back pain intensity and disability and physical activity (MET, hours/week).
Domain | Low back pain intensity | Low back disability |
| Estimated marginal median (95%CI)a | P value | Estimated marginal median (95%CI) a | P value |
| No/low | High | No/low | High |
Model 1b |
Domestic and garden activity | 21.4 (17.1–25.6) | 21.8 (13.2–30.4) | 0.92 | 22.0 (17.8–26.2) | 16.7 (8.1–25.4) | 0.25 |
Walking | 11.1 (9.4–12.8) | 11.0 (7.1–15.0) | 0.98 | 11.4 (9.8–13.0) | 7.6 (2.7–12.5) | 0.15 |
Moderate activity | 31.4 (25.1–37.7) | 28.8 (18.3–39.4) | 0.67 | 32.1 (26.5–37.8) | 19.5 (11.3–28.8) | 0.01 |
Total physical activity | 53.2 (45.1–61.3) | 45.6 (19.0-72.3) | 0.59 | 54.4 (45.3–63.6) | 28.4 (14.5–42.3) | 0.001 |
Sitting time (hours/week) | 34.8 (32.9–36.6) | 33.6 (29.5–38.2) | 0.37 | 34.5 (32.7–36.2) | 37.2 (31.1–43.8) | 0.41 |
Model 2c |
Domestic and garden activity | 23.4 (18.5–28.2) | 21.0 (13.3–28.7) | 0.57 | 23.5 (19.0–28.0) | 14.4 (7.2–21.7) | 0.02 |
Walking | 11.0 (9.2–12.7) | 12.0 (7.0-17.1) | 0.71 | 11.5 (9.8–13.1) | 7.4 (2.6–12.1) | 0.12 |
Moderate activity | 32.4 (26.7–38.1) | 23.2 (10.4–35.9) | 0.17 | 32.1 (26.8–37.4) | 17.5 (10.4–24.7) | < 0.001 |
Total physical activity | 53.2 (44.9–61.4) | 43.5 (19.7–67.2) | 0.44 | 53.9 (44.9–62.8) | 27.3 (13.2–41.4) | 0.002 |
Sitting time (hours/week) | 34.6 (32.8–36.5) | 34.2 (30.0-38.8) | 0.86 | 34.3 (32.6–36.1) | 37.9 (31.8–44.8) | 0.28 |
a CI = Confidence interval; b Model 1: adjusted for age, BMI and depression; cModel 2: model 1 and adjustment for working status. |
Similarly, after adjusting for age, BMI and depression, we found no association between levels of pain intensity and participation in work-related activity (OR (95%CI) = 0.53 (0.28–1.03), p = 0.06), leisure activity (0.96 (0.53–1.73), p = 0.89), active transportation (1.50 (0.80–2.81), p = 0.21) or vigorous activity (1.02 (0.53–1.94), p = 0.96) (Table 4, model 1). These results remained non-significant after further adjustment for working status (Table 4, model 2; Fig. 2).
Table 4
The association between levels of low back pain intensity and disability and participation in physical activity.
| Low back pain intensity | Low back disability |
No/ low (n = 392) | High (n = 71) | OR (95% CI) a | P value | No/ low (n = 425) | High (n = 38) | OR (95% CI) a | P value |
Model 1b |
Work-related activity, n (%) | 142 (36.6) | 16 (23.5) | 0.53 (0.28–1.03) | 0.06 | 149 (35.6) | 9 (24.3) | 0.78 (0.34–1.81) | 0.57 |
Leisure activity, n (%) | 268 (69.1) | 43 (63.2) | 0.96 (0.53–1.73) | 0.89 | 294 (70.2) | 17 (45.9) | 0.41 (0.19–0.85) | 0.02 |
Active transportation, n (%) | 264 (68.0) | 51 (75.0) | 1.50 (0.80–2.81) | 0.21 | 291 (69.5) | 24 (64.9) | 0.95 (0.44–2.06) | 0.89 |
Vigorous activity, n (%) | 120 (30.9) | 17 (25) | 1.02 (0.53–1.94) | 0.96 | 134 (32.0) | 3 (8.11) | 0.16 (0.03–0.70) | 0.02 |
Model 2c |
Work-related activity, n (%) | 142 (36.6) | 16 (23.5) | 0.70 (0.33–1.5) | 0.34 | 149 (35.6) | 9 (24.3) | 1.38 (0.49–3.89) | 0.54 |
Leisure activity, n (%) | 268 (69.1) | 43 (63.2) | 1.00 (0.55–1.83) | 0.99 | 294 (70.2) | 17 (45.9) | 0.44 (0.21–0.94) | 0.03 |
Active transportation, n (%) | 264 (68.0) | 51 (75.0) | 1.40 (0.74–2.65) | 0.30 | 291 (69.5) | 24 (64.9) | 0.89 (0.41–1.95) | 0.78 |
Vigorous activity, n (%) | 120 (30.9) | 17 (25) | 1.01 (0.52–1.97) | 0.97 | 134 (32.0) | 3 (8.11) | 0.17 (0.04–0.75) | 0.02 |
a CI = Confidence interval; bModel 1: adjusted for age, BMI and depression; cModel 2: model 1 plus adjustment for working status. |
Associations Between Low Back Disability And Physical Activity
The associations between physical activity (MET; hours/week) and low back disability are shown in Table 3 and Fig. 1. After adjustment for age, BMI and depression (model 1), there was no significant difference in walking between women with high levels of back disability and those with no or low levels of back disability (MET (hours/week); estimated marginal median (95%CI) = 7.6 (2.7–12.5) vs. 11.4 (9.8–13.0), p = 0.15), but less total (28.4 (14.5–42.3) vs. 54.4 (45.3–63.6), p = 0.001) and moderate physical activity (19.5(11.3–28.8) vs. 32.1 (26.5–37.8), p = 0.01). Moreover, sitting time per week was not significantly different between women with high levels of disability and those with no or low levels of disability (estimated marginal medians (95% CI) = 37.2 (31.1–43.8) vs. 34.5 (32.7–36.2), p = 0.41). After an additional adjustment for working status in model 2, we found that women with high levels of back disability also performed less domestic and garden activities compared to those with no or low levels of disability (MET (hours/week): 14.4(7.2–21.7) vs. 23.5(19.0–28.0), p = 0.02).
After adjusting for age, BMI and depression (Table 4, model 1), we found that women with high levels of back disability were less likely to participate in leisure and vigorous activity (OR (95% CI) = 0.41 (0.19–0.85), p = 0.02 and 0.16 (0.03–0.70), p = 0.02 respectively) compared to women with no or low levels of disability. There were no significant association between levels of disability and participation in work-related (0.78 (0.34–1.81), p = 0.57) and active transportation activities (0.95 (0.44–2.06), p = 0.89). With further adjustment for working status, the results remained unchanged (Table 4, model 2; Fig. 2).