Comparison of self-reported pain intensity, sleeping difficulty, and treatment outcomes of patients with myofascial temporomandibular disorders by age group: a prospective outcome study

Temporomandibular disorders (TMDs) include musculoskeletal and neuromuscular conditions that involve the masticatory muscles, temporomandibular joint (TMJ), and associated structures [1]. They are a subclass of musculoskeletal disorders and cause nondental pain in the orofacial region [1]. TMDs primarily affect young and middle-aged adults rather than children or the elderly [2], although symptoms are frequently observable in the latter populations [3–6]. Most TMDs occur between 20 years and 40 years of age, show a female preponderance [7, 8], and are self-limiting or fluctuate over time [9].

TMDs are associated with many diagnostic features such as internal derangements and myogenous disorders [10]. They can be classified according to the extent of TMJ and muscular involvement. The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) allow standardization and replication of research on the most common forms of TMDs [11]. Symptoms of TMDs can accordingly be investigated by diagnostic subgroups. Patients with chronic TMDs in the myofascial pain subgroup (i.e., RDC/TMD, Axis I, Group I) reportedly have greater dysfunctionality, higher pain intensity, and greater psychological difficulties, compared to patients in the intracapsular pain subgroup (i.e., RDC/TMD, Axis I, Group II or Group III) [12, 13]. In addition, young patients with myofascial pain have significantly greater difficulty in sleeping, compared to patients with TMJ-related problems [14].

Symptoms of joint-related TMDs resolve with minimal care [15]. However, symptoms of myogenous TMDs can become chronic because many patients focus less on tightness in the masticatory muscles or on the presence of trigger points, which may also be responsible for their myofascial pain. Patients with chronic myogenous TMDs may have persistent central sensitization and psychological comorbidity that is similar to patients with chronic pain [16]. Therefore, early intervention is needed to reduce muscle tenderness and associated disability. However, few studies have compared the subjective symptoms of TMDs by age group [17–19].

In this study, we aimed to compare self-reported pain intensity, sleeping difficulty, and treatment outcomes of patients with myofascial TMDs among three age groups. We hypothesized that young patients are more likely to have mild symptoms and their symptoms are easy to treat, whereas older patients are more likely to show severe symptoms, which are difficult to treat.

This study focused on patients with myofascial TMDs and compared self-reported symptoms between three age groups. From the findings of previous studies [5, 26], we hypothesized that young patients are more likely to have mild symptoms and their symptoms are easy to treat, whereas older patients are more likely to show severe symptoms, which are difficult to treat. However, our present findings did not support this hypothesis: pretreatment symptoms of myofascial TMDs were similar in all age groups and no differences were found in the treatment outcomes among the different age groups.

A study of consecutive patients of all ages showed that 85.4% of patients who sought treatment for TMDs were females [27], which was consistent with our findings in each age group (i.e., more than 80%). Therefore, TMDs show a female preponderance at all ages. Temporomandibular disorder conditions such as myofascial pain are associated with female sex [28]. Women with TMDs report more severe physical symptoms, compared to men [29]. However, ratings of pain rarely show significant sex differences [30]. In our study, pain intensity was not significantly different between the sexes, which may have been influenced by the selection bias associated with the patients’ seeking health care [31].

Levitt and McKinney [29] report that the pain severity of patients with TMDs is the same across age groups and that the severity of symptoms is greater in groups in which TMDs have existed for a long duration. We did not study the natural course of the disease in the present study; however, the patients with myofascial TMDs experienced similar pain intensity, regardless of age. From our results, the duration of treatment was not different between the age groups, which suggests a similar duration of TMDs. Furthermore, each age group showed a wide range in the standard deviation for each symptom score, which indicated different levels of severity in each age group. These factors may have influenced the lack of a significant difference in pain intensity associated with myofascial TMDs. However, even patients younger than 20 years have headache and neck pain intensity that is similar to that of older groups. Individuals who develop TMDs are more likely to describe comorbidities such as headache and other body pain [32, 33]. Clinicians should therefore pay more attention to young patients with myofascial TMDs who complain of high-intensity pain.

Myogenous pain is treated by various strategies such as trigger point injections, vapocoolant spray and stretch, transcutaneous electrical nerve stimulation, biofeedback, posture correction, tricyclic antidepressants, muscle relaxants and other medications, and by addressing perpetuating factors [34]. Fricton [34] states that the complexity of the treatment program needs to match the complexity of the patient’s condition. In the current study, pharmacotherapy was provided by one of two board-certified orofacial pain specialists and included analgesics (nonsteroidal anti-inflammatory drugs), muscle relaxants (cyclobenzaprine, 10 mg), and low-dose tricyclic antidepressants (amitriptyline, 10–25 mg). Physical therapy was provided by a licensed therapist and included a home-care program (i.e., self-management and exercise regimen), posture training, mobilization, and the use of physical agents such as ultrasound or vapocoolant spray. Dental treatment other than orthopedic appliances (i.e., interocclusal splints) was not provided to most patients.

The treatment options and duration did not significantly differ by age group, although medications tended to be prescribed more frequently in groups M2 and M3. The average duration of treatment was more varied in group M3. We did not determine the treatment periods of each patient because the treatment interval varied among the age groups. We defined the treatment duration as the time from the first visit to the last visit. Further, older patients may have a chronicity of symptoms [5]. These factors may have influenced the large dispersion of treatment duration in group M3.

A study that compared treatment outcomes of young patients (20–30 years) and elderly patients (50–70 years) with TMDs [18] showed that, although 54% and 38% of the respective groups had a muscle disorder diagnosis, both groups responded equally well to a conservative treatment regimen and experienced marked reduction in pain. In the present study, the patients in all age groups demonstrated a significant decrease in jaw/face pain after the treatments, and the changes in the scores were not different between the age groups. Therefore, conservative treatment methods are effective for myofascial TMDs at all ages.

Approximately one-third of patients with TMDs report poor sleep quality [1]. Numerous factors such as medical condition, mental disorders, breathing disorders during sleep, or other sleep disorders can induce insomnia symptoms [35]. A population-based study reports that insomnia is one consequence of chronic pain [36]. A recent epidemiological study reports that the prevalence of difficulty in maintaining sleep increased with age, reaching nearly 50% in elderly individuals (i.e., older than 60 years) [37]. Older patients are more likely to have a physical illness—especially arthritis and heart disease—or have a painful physical affliction such as back pain. These physical conditions may cause older patients to experience greater sleeping difficulty, compared to young patients. In our study, groups M2 and M3 had greater pretreatment sleeping difficulty but had a significant post-treatment improvement. They also reported a similar level of sleep difficulty as that of the young patients. A meta-analysis of fibromyalgia showed that patients treated with cyclobenzaprine were three times more likely to report moderate reductions in individual symptoms, particularly in sleep [38]. In the present study, medications (i.e., muscle relaxants) and a home-care program (i.e., sleeping position and using appropriate pillows) may have improved self-reported sleep difficulty in the older patients.

We did not assess treatment effectiveness. Because of this limitation, we cannot describe the most effective treatment for symptoms of myofascial TMDs in young or elderly patients. However, tailored treatment protocols are necessary for patients with TMDs. Further well-designed studies are needed to clarify the effects of each treatment and the effects of patient compliance with a home-care program on reducing orofacial pain and difficulty in sleeping.

Pain intensity associated with myofascial TMDs does not differ by age, but older patients experience greater sleeping difficulty, compared to young patients. Conservative treatment strategies can reduce pain in the jaw or face region at all ages. Treatment outcomes of self-reported pain intensity and sleeping difficulty are not different between different age groups. Clinicians should carefully consider the age-related characteristics of patients with myofascial TMDs when developing appropriate management strategies.