The present study aimed to examine the psychometric properties of the POAM-P-J. We adopted the 3-factor structure of the POAM-P, but some fit indices showed poor fit to data. The POAM-P-J, meanwhile, showed good internal consistency and test-retest reliability. Overall, avoidance and overdoing were associated with higher pain severity, pain interference, and anxiety whereas pacing was not associated with these outcomes.
The structural validity of the POAM-P-J remains questionable. Item 30 displayed a low factor loading, which is similar to the Turkish version of the POAM-P [17]. In the Turkish version of the POAM-P, item 30 was kept so that the original scale structure was not distorted. We followed the Turkish version of the POAM-P, so the item 30 retained. In the current study, sample bias may have contributed to the poor to acceptable fit of POAM-P-J. Although the samples of the original and Turkish versions of the POAM-P consisted of individuals with chronic primary pain with an average age of 40 years [4, 17], the sample in this study consisted of individuals with pain in the lower limbs with an average age of 60 years. Thus, a possibility exists that the sample may include individuals with knee osteoarthritis, which led to their tendency to display less avoidance or overdoing compared with individuals with chronic primary pain. However, structural validity was only confirmed for the Turkish and Japanese versions of the POAM-P. It is necessary to examine the factor structure in different populations in the future.
The POAM-P-J has shown good reliability values. However, the number of participants who answered the POAM-P-J twice (N = 18) was small in the current study. The previous study reported that the POAM-P has good test-retest reliability with a sufficient sample size [14]. Succeeding research efforts would therefore need to examine the test-retest reliability of the POAM-P-J with enough Japanese samples.
Meanwhile, according to interscale correlations, avoidance was moderately associated with pacing, and studies have reported the same extent of association between the two (r = 0.46–0.56) [6, 14, 15, 19]. According to a meta-analysis, some pacing items contain pain-contingent behaviors, with some overlap existing between pacing and avoidance [32].
Concurrent validity results showed a positive association between the avoidance and overdoing scales and measures of pain-related outcomes. Such an association is the same as that in the original study [4] and is considered to confirm the concurrent validity of the POAM-P-J. However, overdoing was not significantly associated with depression. Hasenbring, who proposed the avoidance–endurance model [7], identified two types of overdoing: one associated with positive affect and the other associated with depressive mood. The overdoing scale of the POAM-P might include these two types, which can therefore be linked to the lack of association between depression and POAM-P-J’s overdoing scale.
Contrary to the hypothesis, the pacing scale was not significantly associated with pain-related measures. A possible reason would be that pacing may have adaptive and maladaptive components. While pacing aims to increase activity levels, conserve energy for important activities, and reduce pain [9, 10, 15], patients can also perceive its use as limiting compared with activity levels before pain onset [6].
This study has several limitations. First, the number of people who answered the POAM-P-J twice was small. Second, we did not know each participant’s condition, as the inclusion criteria included only a pain history of three months or more. Third, the participants’ average age was high, and the proportion of those who suffered from lower-limb pain was high as well. Therefore, sampling bias might have occurred. In this study, unlike previous ones [4, 6, 14, 15, 19, 20], overdoing was not significantly associated with avoidance or pacing. Such sampling bias might have affected the relation between overdoing and two other activity patterns.