Sex-specific Differences in Pain Intensity in Danish Physiotherapy Patients

BACKGROUND
Sex appears to be an important contributor to differences in the perception and experience of pain, with a growing body of evidence reporting sex-specific differences in both the prevalence of painful conditions, in response to pain management interventions, and in response to experimentally induced pain. However, studies have to a lesser extent focused on differences in self-reported pain intensity in people who seek care for musculoskeletal pain. The aim of this study was to describe sex-specific differences in primary symptom site and pain intensity in patients seeking care in Danish private physiotherapy clinics.

METHODS
Cross-sectional study of patients seeking care in Danish private physiotherapy clinics within the FysioDanmark® network between January 2017 and March 2020. Data were available via the FysioDanmark® clinical database and obtained from questionnaires distributed to patients prior to their first consultation. Patients were asked to indicate the primary symptom site for which they sought treatment. From this information, patients were categorised as having symptoms in one of the following categories: Back; Neck; Shoulder; Hip; Knee; Ankle/foot; and Non-specific. Pain intensity experienced by patients ‘most of the time’ was assessed using a 11-point Numeric Rating Scale (NRS) ranging from 0 (no pain) to 10 (worst imaginable pain) for the primary symptom site. Data on primary symptom site was presented as percentage distribution and 95% confidence intervals (95%CI). Pain intensity for males and females was reported as median, interquartile range (IQR), and upper and lower adjacent values stratified by primary symptom site and age (10-year intervals age groups).

RESULTS
In total 64,505/186,808 patients (35%) responded to the questionnaire. Patients whose treatment was fully paid by the healthcare system (n=939) were excluded as they were not comparable to the other patients (e.g. severe disability). Data from the remaining 63,566 first visits by 61,097 persons constituted the final study sample. Included patients had a mean age of 41.8 (SD 16.2) years and 57% were female. The age distribution was similar for males and females. In total, 23% (95%CI: 22.6 to 23.2) of the patients consulted a physiotherapist for back symptoms, 20% (95%CI: 19.5 to 20.1) non-specific symptoms, 16% (95%CI: 15.6 to 16.2) shoulder symptoms, 15% (95%CI: 14.5 to 15.1) knee symptoms, 13% (95%CI: 12.7 to 13.1) for neck symptoms, 8% (95%CI: 7.6 to 8.1) ankle/foot symptoms, and 5% (95%CI: 4.7 to 5.1) hip symptoms. In males, the most common reason for consulting a physiotherapist was back symptoms followed by shoulder and non-specific symptoms, which together constituted 62% of all reported problems. In females, the most common reason for consulting a physiotherapist was non-specific symptoms, followed by back and neck symptoms, which together constituted 57% of all reported problems. Overall, females reported slightly higher pain intensity compared to males (4 (IQR: 2 to 6) vs. 3 (IQR: 2 to 5). When stratifying by primary symptom site, females reported slightly higher pain intensity (1 point) compared to males across all primary symptom sites. Similarly, females reported slightly higher pain intensity compared to males in all age groups (1 to 1.5 points), except in the youngest age group. Females in older age groups reported higher pain intensity than females in the younger age groups. This was not observed to the same extent in males.

CONCLUSION
Among patients seeking care in Danish private physiotherapy clinics, males most commonly presented with back symptoms, followed by shoulder and non-specific symptoms, whereas females most commonly presented with non-specific symptoms, followed by back and neck symptoms.
In general, females reported higher pain intensity compared to males across the different primary symptom sites and age groups (10-year intervals). Also, females in older age groups reported higher pain intensity than females in the younger age groups. This was not observed to the same extent in males. These findings provide knowledge on a large group of patients consulting physiotherapists in the real-world clinical setting.