A prospective study of dietary patterns and the incidence of endometriosis diagnosis

Background: Although endometriosis is a common condition—affecting ∼10% of premenopausal individuals—its etiology is unknown. Diet receives a lot of attention from patients, but studies of the role of diet are limited. Examining dietary patterns is essential to provide new insight. Objective: We sought to determine whether dietary patterns are associated with laparoscopically-confirmed endometriosis diagnosis. Study Design: We conducted a prospective cohort study among 81,997 premenopausal participants of the Nurses’ Health Study II, who were followed from 1991–2015. Diet was assessed with validated food frequency questionnaires every 4 years. We examined 6 dietary patterns: Western, Prudent, Alternative Healthy Eating Index, Dietary Approaches to Stop Hypertension, an estrogen-associated pattern, and a proinflammatory pattern. Cox proportional hazard ratios and 95% confidence intervals were used to quantify the association between each of these patterns and laparoscopically-confirmed endometriosis diagnosis. Results: Three thousand eight hundred ten incident cases of endometriosis were diagnosed during 24 years of follow-up. Adherence to the Alternative Healthy Eating Index, reflecting a healthier dietary pattern, was associated with a 13% lower risk of endometriosis diagnosis (fifth vs first quintile 95% confidence interval, 0.78–0.96; P_trend=.02). Participants in the highest quintile of the Western dietary pattern, characterized by high intake of red meat, processed meat, refined grains, and desserts, had a 27% higher risk of endometriosis diagnosis than those in the lowest quintile (95% confidence interval, 1.09–1.47; P_trend=.004). The Prudent, Dietary Approaches to Stop Hypertension, and estrogen-associated dietary patterns did not demonstrate clear associations with endometriosis risk, and there was the suggestion of a higher risk of endometriosis diagnosis among those with a higher proinflammatory diet score (hazard ratio for fifth vs first quintile, 1.10 [95% confidence interval, 0.99–1.23]; P_trend=.01). Conclusion: Our results suggest that consuming a dietary pattern that adheres to the Alternative Healthy Eating Index-2010 recommendations lowers the risk of endometriosis diagnosis, potentially through a beneficial impact on pelvic pain. In addition, consuming a less healthy diet high in red/processed meats and refined grains may have a detrimental impact on endometriosis symptoms.