Fig. 2

A Age (years) data from each individual study according to the age criterion sub-group. Circles depict age as reported by the study and the solid dots depict the weighted mean within the sub-group. The solid horizontal line illustrates the reference value (49.2 years), which is the weighted mean among studies that reported the value but did not have an age criterion. B BMI (kg/m²) data from each individual study according to the BMI criterion sub-group. Circles depict BMI as reported by the study and the solid dots depict the weighted mean within the sub-group. The solid horizontal line illustrates the reference value (29.2 kg/m²), which is the weighted mean among studies that reported the value but did not have a BMI criterion. C Pain (VAS) data from each individual study according to the pain criterion sub-group. Circles depict pain as reported by the study and the solid dots depict the weighted mean within the sub-group. The solid horizontal line illustrates the reference value (6.9 VAS), which is the weighted mean among studies that reported the value but did not have a pain criterion. D Symptom duration (months) data from each individual study according to the symptom duration criterion sub-group. Circles depict symptom duration as reported by the study and the solid dots depict the weighted mean within the sub-group. The solid horizontal line illustrates the reference value (16.2 months), which is the weighted mean among studies that reported the value but did not have a symptom duration criterion