Introduction

Pain is the most common sensation reported by both adult and paediatric patients. The International Association for the Study of Pain (IASP) defines pain as "An unpleasant sensory and emotional experience associated with, or similar to that associated with actual or potential tissue damage¹-⁴. Pain has received different classifications focused on providing a description of it in accordance with the origin (nociceptive or neuropathic) and the temporality (acute and chronic) thereof. In 2019, the international classification of diseases (ICD-11) was updated, which, together with the IASP, included chronic primary pain⁵-¹⁰. Chronic primary pain has an obscure etiology and pathophysiology, and is defined as pain in one or more anatomical regions that persists or recurs for more than 3 months and is associated with significant emotional distress (for example, anxiety, anger, frustration and depression) and/or significant functional disability (interference in day-to-day activities and participation in social roles), and the symptoms thereof are not better explained by any other diagnosis⁹.

The prevalence of pain in pediatric patients is 86%; up to 80.9% of hospitalised children suffer pain in the first 24 hours. Regarding chronic pain, a 2011 systematic review provided estimates of prevalence for headache (8% to 83%), abdominal pain (4% to 53%), and back pain (14% to 24%), all of which are now part of the classification of chronic primary pain¹¹-¹⁵. The purpose of the ICD is to facilitate epidemiological reports, while being familiar with the prevalence of primary chronic primary pain in pediatric patients with chronic pain will enable us to view this type of pain as a pathology present in this age group.

Materials and method

A retrospective, observational and cross-sectional study was conducted on the records of patients of both sexes aged 2 to 17 years treated at the "Dr. Eduardo Liceaga" General Hospital of Mexico Pain Clinic from January 2014 to October 2019, to which an algological diagnosis was added based on ICD-11. The data was collected and analysed in Excel format with measures of central tendency and Chi Square for non-parametric data using Sigma Plot 14.0 software. The protocol was accepted by the hospital's research and bioethics committee under registration number DECS/JPO-CT-580-2020.

Results

An analysis of 184 patients was conducted, 51.6% of which registered chronic secondary pain (48.4% female and 51.6% male). The remaining 48.4% registered chronic primary pain. The mean (M) age was 12.5 years, the median (Me) age 14 years and the mode (Mo) 17 years. It should be stressed that the results do not change significantly with respect to gender: women.

The prevalence was higher for head and neck pain (62.9%), followed by musculoskeletal pain (23.5%), visceral pain (21.2) and complex regional pain syndrome (2.2%); 14.6% of the patients registered pain in more than one region. The causes in order were chronic migraine (47.2%), followed by chronic tension headache and irritable bowel syndrome (15.7% each), limbs (11.2%), thoracic pain (6.7%), lower back pain (5.6%), abdominal pain (4.4%), type 1 complex regional pain syndrome (2.2%) and pelvic pain (1.1%). When conducting an analysis of prevalence by gender, we observed that visceral pain in women comes in second place, while in men it is musculoskeletal pain (Figure 1).

Figure 1 Prevalence of chronic primary pain in pediatric patients by gender. We observed a graph with the prevalence of complex regional syndrome (1), chronic primary head and orofacial (2), visceral (3) and musculoskeletal pain (4), in female (blue) and male (grey) patients. 

Head and neck pain

Chronic head and neck pain seems to be focused on 2 items, chronic migraine (75%) and chronic tension headache (25%). In both men and women the prevalence is higher for chronic migraine (50% and 45.8% respectively). However, the ratio between women with respect to men is 1.8:1 and 3.6:1 respectively. The most affected population is adolescents with 69.6%: only 15% were schoolchildren and 5.4% preschoolers (Figure 2).

Figure 2 Prevalence of chronic migraine and chronic tension-type headache by gender and age in pediatric patients. 

Discussion

Estimates of the prevalence of chronic pain in the pediatric population are reported to be 20% to 35%. In adult patients with chronic pain, it is usually of a secondary origin, while in pediatric patients, the main causes of chronic primary pain include headaches and irritable bowel syndrome¹⁶-¹⁷. This study registered a prevalence of 48.4% for chronic primary pain, and coinciding with the previously reported bibliography a higher incidence of chronic pain was observed in women than in men (57% x 43%). However, when specifying secondary chronic pain the prevalence it is almost the same in both sexes (48.4% x 51.6%), while chronic primary pain is more prevalent in women (66.3%) (Figs. 3-5).

Figure 3 Prevalence of chronic primary pain in pediatric patients aged 2 to 17 years. 

Figure 4 Prevalence of chronic primary pain in female pediatric patients aged 2 to 17 years. 

Figure 5 Prevalence of chronic primary pain in male pediatric patients aged 2 to 17 years. 

Chronic pain has multiple associated physical, psychological and social factors, and even today the IASP has taken the psychological environment into account for the diagnosis of chronic primary pain. Chronic pain in pediatric patients has been shown to be associated with higher rates of mental health disorders such as anxiety (21.1% x 12.4% of pain-free adolescents) and depressive disorders (24.5% x 14.1%)¹⁷. The data was consistent, where adolescents were the most affected and the main causes of pain were mood-related pathologies.

Conclusions

The prevalence of chronic primary pain in pediatric patients is 48.4%, 66.3% of which are women and 33.7% men. The most affected age group is adolescents in both sexes.