Association of tea drinking and dysmenorrhoea among reproductive-age women in Shanghai, China (2013–2015): a cross-sectional study

OBJECTIVES: To investigate the association between tea drinking and dysmenorrhoea among women of reproductive age. DESIGN: A cross-sectional study based on Shanghai Birth Cohort Study. SETTING: Two preconceptional care clinics in Shanghai, China. PARTICIPANTS: 1183 women of reproductive age who sought preconceptional care were recruited from August 2013 to April 2015. PRIMARY AND SECONDARY OUTCOME MEASURES: Participants were asked if they had pelvic pain associated with menstrual bleeding during the past 12 months and to further grade the intensity of menstrual cramp as mild, moderate and severe. Multinomial logistic regression was performed to assess the association of tea drinking and dysmenorrhoea. Other information, such as demographic and lifestyle factors, was also collected and assessed in relation to dysmenorrhoea. RESULTS: The prevalence of dysmenorrhoea was 57.8%, among whom 10.4% and 3.5% had moderate and severe dysmenorrhoea, respectively. Tea drinking was associated with a lower prevalence of dysmenorrhoea (adjusted OR [aOR]=0.68, 95% CI 0.50 to 0.93 for mild dysmenorrhoea; aOR=0.59 (95% CI 0.32 to 1.04) for moderate-to-severe dysmenorrhoea). Green tea and oolong tea appeared to have most reduction in the prevalence of dysmenorrhoea (for mild dysmenorrhoea: green tea: aOR=0.63 (95% CI 0.44 to 0.90) and oolong tea: aOR=0.60 (95% CI 0.35 to 1.03); for moderate-to-severe dysmenorrhoea: green tea: aOR=0.42 (95% CI 0.20 to 0.85) and oolong tea: aOR=0.34 (95% CI 0.11 to 1.09)). CONCLUSIONS: Consumptions of green tea and possibly oolong tea were associated with a lower prevalence of dysmenorrhoea.