Matching males and females undergoing Shouldice repair using a prospective, longitudinal design.

Background: Sex differences in chronic postsurgical pain have been reported, with the main findings indicating that females experience a greater incidence and severity of pain than males; however, it remains unclear to what these sex differences are attributable. We sought to compare pain and related psychological factors between a matched sample of male and female patients 3 months and 1 year after Shouldice repair.

Methods: Male and female participants who underwent Shouldice repair were manually matched 1:1 and compared on 10 variables: age, body mass index, smoking status, preoperative depression and anxiety scores, living status (alone or with others), American Society of Anesthesiologists physical status health classification, preoperative chronic pain, preoperative hernia pain, preoperative pain catastrophizing scores, and nerve handling during surgery. Data on pain were collected from questionnaires administered 3 months and 1 year postoperatively, and data on participant clinical characteristics were collected from operative notes and patient charts.

Results: There were 28 matched male-female pairs at 3 months and 21 at 1 year. The average age preoperatively was 56.18 ± 12.48 years. At 3 months postoperative, 18 females and 6 males had pain (p = 0.001), with females reporting more frequent (p = 0.004) and longer durations (p = 0.005) of pain. The 3-month postoperative Brief Pain Inventory Numeric Rating Scale scores (0-10) showed that in terms of pain severity, females had higher "worst pain" (1.61 ± 1.85 v. 0.32 ± 0.77, p = 0.002), "average pain" (0.86 ± 1.08 v. 0.14 ± 0.45, p = 0.002), and "pain now" (0.43 ± 1.20 v. 0 ± 0, p = 0.010) scores than males. Significant differences were not found in the incidence, severity, frequency, or duration of pain between females and males at 1 year.

Conclusion: After matching on important confounders, sex differences were found in pain frequency, duration, incidence, and severity at 3 months after Shouldice repair. However, by 1 year after surgery the differences were no longer significant.

Trial registration: Clinicaltrials.gov # NCT03986060.