The effect of combined oral contraceptives and age on dysmenorrhoea: an epidemiological study.

BACKGROUND Combined oral contraceptives (COCs) are widely advocated as treatment for primary dysmenorrhoea, but their efficacy has been questioned in a Cochrane review. The aim of this study was to evaluate COCs and the influence of age on the severity of dysmenorrhoea. METHODS Postal questionnaires regarding weight/height, contraception, pregnancy history and other reproductive health factors were sent to random samples of 19-year-old women born in 1962 (n = 656), 1972 (n = 780) and 1982 (n = 666) resident in the city of Gothenburg in 1981, 1991 and 2001. The responders were assessed again 5 years later at the age of 24 years. Current severity of dysmenorrhoea was measured on each occasion by a verbal multidimensional scoring system (VMS) and by a visual analogue scale (VAS). RESULTS The severity of dysmenorrhoea was lower (P< 0.0001) in COC users compared with non-users. In a longitudinal analysis of the severity of dysmenorrhoea, COC use and increasing age, independently of each other, were associated with the severity of dysmenorrhoea (COC use, VMS score: a reduction of 0.3 units/VAS: a reduction of 9 mm, both P< 0.0001; increasing age, VMS score: a reduction of 0.1 units per 5 years, P< 0.0001/VAS: a reduction of 5 mm per 5 years, P< 0.0001). Childbirth also reduced the severity of dysmenorrhoea (VAS, P< 0.01 with a reduction of 7 mm). Women from the 82-cohort reported a greater severity of dysmenorrhoea compared with the 62 and 72 cohorts at both 19 and 24 years of age. CONCLUSIONS In this longitudinal case-control study, COC use and increasing age, independent of each other, reduced the severity of dysmenorrhoea. COC use reduced the severity of dysmenorrhoea more than increasing age and childbirth. There was a trend over time regarding the severity of dysmenorrhoea where women from the 82-cohort reported a greater severity of dysmenorrhoea compared with the 62 and 72 cohorts.