Primary dysmenorrhea (PD) is menstrual pain without associated pelvic disease, while secondary dysmenorrhea (SD) is associated with conditions such as endometriosis. PD has a prevalence of 71% worldwide and can have a significant impact on women's functioning (i.e., “an umbrella term for body function, body structures, activities and participation, and it denotes the positive or neutral aspects of the interaction between a person’s health condition(s) and that individual’s contextual factors”). However, its impact remains neglected. Assessing how pain severity affects functioning using instruments developed for people with dysmenorrhea is essential to understanding its broader impact.

To analyze the impact of the severity of PD on functioning in adult Brazilian women with PD using a new instrument.

This is a cross-sectional and online study conducted between January 2022 and March 2023. We included Brazilian adult women between 18 and 50 years old with a report of PD for at least the previous three months. We excluded pregnant women, those with up to six months postpartum, transgender men, and women with a clinical diagnosis of SD. Severity of PD was rated by the single-item Numerical Rating Scale (NRS) for the last period, with response options ranging from zero “no pain” to 10 “the worst imaginable pain”. PD-related functioning was assessed using the Dysmenorrhea-Related Impact on Functioning Scale (DIFS), which has two subscales, “Bodily functions” and “Daily activities and social participation”. Higher scores on the Bodily functions scale, Daily activities and social participation scale, and the total DIFS score indicate a greater impact of dysmenorrhea on bodily functions, daily activities and social participation, and functioning, respectively. Data were analyzed using linear regression in SPSS® 26.

A total of 2382 women (27.1 ± 7 years) participated in the study. Age at menarche, menstrual cycle length, and severity of PD in the last period were 12.2 ± 1.6 years, 28.2 ± 4.6 years, and 6.5 ± 2.3 points, respectively. The “Bodily functions”, “Daily activities and social participation”, and DIFS total score were 14 ± 4.7 points, 31.7 ± 17.2 points, and 45.7 ± 20.6 points, respectively. Severity of PD has a significant impact on bodily functions (p < 0.001, R²adj = 0.197), daily activities and social participation (p < 0.001, R²adj = 0.208), and functioning (p < 0.001, R²adj = 0.233) of participants. On average, a one-point increase in PD severity negatively impacts bodily functions by 0.910 points (95%CI 0.836 - 0.984), daily activities and social participation by 3.407 (95%CI 3.140 - 3.674), and functioning by 4.317 (95%CI 4.002 - 4.432).

Our findings show that the severity of PD has a significant impact on women&apos;s functioning, affecting both bodily functions and daily activities and social participation. Future studies should explore the long-term impact of dysmenorrhea and evaluate the effectiveness of interventions to minimize its effects.

The findings highlight the importance of incorporating PD management into physical therapy practice and public health policy. Educational programs and therapeutic interventions should address pain management and promote strategies to improve women&apos;s functioning.