The impact of chronic orofacial pain on health-related quality of life

2.1 Subjects

This cross-sectional, observational study is part of the multi-center study KROKIETA, Chronic Pain, Life Style Factors and Quality of Life, study in Finland. The study patients were recruited from facial pain clinics at three hospitals in Finland (Turku and Kuopio University Hospitals and Central-Finland Central Hospital) between November 2013 and November 2016. Consecutive patients aged 18–75 years referred to pain management in tertiary care because of chronic OFP were invited to participate in the study and were provided with written information about the study protocol (n=164). Headache patients were not included. Neither were patients with cancer-related pain nor patients unable to answer the study questionnaire independently. The Ethics Committee of the Helsinki University Hospital approved the study (decision no. 29/13/03/00/2012), and each hospital gave permission for the study.

Four patients refused to participate. Nine patients from the remaining sample of 160 patients did not return questionnaires or answered them incompletely. The final number of patients included in the study was 151 (119 females, mean age 50 years, SD 15 years). All participants gave written informed consent.

2.2 Measures

4.1 Main findings

The results of the study indicate that chronic OFP substantially reduces the HRQoL of these patients. The self-reported HRQoL of OFP patients (0.824) was statistically significantly and clinically importantly lower than that of an age- and gender-standardized sample of the Finnish population (0.929). From the different dimensions of health described by the 15D, discomfort and symptoms, sleep and vitality were most affected. The results also indicated convergent validity between the results of the 15D and interference in daily functioning caused by the pain by showing a statistically significant linear decrease in the 15D dimension score values and in most individual dimension values with increasing pain interference, as well as an inverse correlation (r=−0.65) between the 15D score and pain interference. These findings suggest that 15D is an appropriate instrument for use in the assessment of HRQoL in OFP patients.

4.2 Comparison with other chronic conditions

The impact of major chronic health conditions on HRQoL was investigated in a population-based survey in Finland using the 15D [31]. Compared with the results of that study, the findings of the present study indicate that HRQoL of chronic OFP patients is poorer than that of patients suffering from many types of chronic health conditions such as cancer (0.855), depression (0.841), back (0.874) or neck (0.879) problems or osteoarthritis of the hip and knee (0.873), and comparable to that of patients with serious psychiatric conditions (0.829) or coronary heart disease (0.821). Looking at the results of 15D studies with similar study settings, the perceived burden of chronic OFP seems less than that of patients admitted to secondary care because of depression (0.729) [32], but similar to that of secondary care rheumatoid arthritis patients (0.822) [33]. That chronic OFP seems to impact HRQoL more than many serious somatic health conditions may reflect the comprehensive nature of suffering or distress often connected to chronic pain problems. Some of the lowest mean 15D scores (0.710 and 0.714) reported in outpatient populations were those found in recent studies on tertiary care chronic pain patients [8], [34]. The difference in the perceived burden between the tertiary care pain patients and the orofacial pain patients of the present study may be due to the more devastating effects of bodily pains on e.g. mobility and usual activities, compared with those caused by orofacial pain conditions. Having musculoskeletal pain only in the craniomandibular region impairs HRQoL less than more widespread musculoskeletal pain [35]. Similarly, the impact of trigeminal neuropathic pain on HRQoL is less than that of conditions involving bodily neuropathic pains [36].

With one exception [9], earlier studies on HRQoL have focused on different, specific orofacial pain conditions. Further, they have utilized instruments other than the 15D, the SF-36 [20], [37], [38], [39] or EQ-5D [36], [40], [41]. As different HRQoL instruments measure different constructs they can produce variable results in the same patient populations [13], [42]. Thus, direct comparisons of the present results and those of earlier studies are not feasible. However, all studies have shown that chronic orofacial pain conditions impact negatively HRQoL [9], [35], [36], [37], [38], [39], [40], [41].

4.3 HRQoL and pain interference

Statistically significant and clinically important decreases in the mean 15D score and marked, statistically significant decreases in most dimension values were noted with increasing pain interference. In particular, the dimensions discomfort and symptoms, sleeping and vitality deteriorated with increasing pain interference. These are the same dimensions on which OPF patients differed most from the general population. An impairment of most of those 15D dimensions, which are associated with psychosocial aspects of health, has also been noted in another chronic pain population in tertiary care [8].

Patients in the lowest interference tertile, i.e. those reporting low pain-related interference, judged their HRQoL to be as good as that of the general population sample with the exception of the dimension of discomfort and symptoms where the participants had lower values. However, patients in the highest interference tertile reported impaired HRQoL with marked deterioration on almost all 15D dimensions. An association of pain interference and HRQoL, which has also been noted in other studies on chronic pain populations [8], [14] as well as in chronic orofacial pain [41], is logical as both of these measures comprehensively assess the impact of pain. Their concomitant use can, however, be an advantage given the fluctuating manner of orofacial pains, as the reference period of the BPI/interference measure and of the 15D are different (the last week vs. current). Further, IMMPACT [43] and VAPAIN [44] recommendations for core outcome domains and measures in chronic pain trials state that several outcomes should be used, including both pain interference and HRQoL measures.

As in previous studies on chronic OFP patients [16], [17], [18], [19], significant increases in pain intensity, pain duration, presence of pain in other areas, depressive symptoms, anxiety and sleep disturbances, were noted with increasing pain interference in the present study, with a decrease in leisure time physical activity. These results support the validity and discriminative power of the interference division (tertiles) used in the present study.

4.4 Strengths and limitations

The present study is the first to compare the HRQoL of chronic orofacial pain patients with that of an age- and gender-standardized sample of the general population. The use of the generic and preference-based 15D instrument also makes the comparison of the impact of orofacial pain with that of other chronic pains or other chronic health conditions possible. The 15D instrument used in the present study has been shown to fare as well as or better than other preference-based HRQoL instruments [13], [14], [22], [42]. In addition to the single index score measure, the 15D can be used as a profile, which describes the 15 dimensions of health. An analysis of the impaired dimensions gives insight into which aspects of health are affected by a given condition and consequently relevant targets for treatment intervention. Further, with the established MIC value, the 15D is a suitable measure for intervention studies. By showing the usefulness of the 15D in the assessment of chronic OFP, the present study may contribute to the implementation of HRQoL assessment as one of the core outcome measures in future treatment studies on chronic OFP as advised by the IMMPACT recommendations [43].

Limitations of the present study are that the participants were tertiary care facial pain patients, i.e. a selected group of challenging pain patients, and thus the results may not be applicable to all chronic OFP patients. Moreover, the participants were a heterogenous group of OFP patients, not patients with specific orofacial pain diagnoses, which may impact the HRQoL differently. Furthermore, a generic HRQoL instrument was used, which has a possible disadvantage of being less sensitive than condition-specific instruments, as it may not capture all the relevant aspects of the disease. Thus the concomitant use of generic and condition-specific instruments in HRQoL studies is recommended, albeit especially in studies focusing on responsiveness to treatment or disease progression, as these measures are able to assess in greater detail the impact of chronic pain condition on HRQoL [5]. However, to our knowledge, no validated condition-specific instruments exist for chronic orofacial pain conditions.