Background: Observations of increasing asthma incidence, decreasing age at menarche, and common risk\r\nfactors have led investigators to hypothesize potential associations of age at menarche or menstrual characteristics\r\nwith incidence of adult onset asthma. We evaluated these associations among reproductive age women.\r\nMethods: Study participants were selected from among women enrolled in a pregnancy cohort study. Information\r\non age at menarche, menstrual characteristics, and history of asthma was collected using interviewer-administered\r\nquestionnaires. Adult onset asthma was defined as asthma first diagnosed after onset of menarche. Women who had\r\nno information on asthma and menstrual history and those who were diagnosed with asthma before menarche were\r\nexcluded. A total of 3,461 women comprised the analytic population. Logistic regression was used to estimate adjusted\r\nrelative risk (aRR) and 95% confidence intervals (95% CI) relating age at menarche and menstrual characteristics with\r\nadult onset asthma.\r\nResults: Mean age at menarche was 12.8 years (standard deviation=1.46). Among study participants, 7.5%\r\nwere diagnosed with asthma after the onset of menarche. After controlling for potential confounders (age, race, body\r\nmass index, and socio-economic status), women who had early menarche (<12 years old) had 60% higher risk of\r\nbeing diagnosed with adult onset asthma as compared with women who did not have early menarche (= 12 years old)\r\n(aRR=1.59, 95% CI 1.19-2.13). Menstrual irregularities or abnormal (short or long) cycle length were not associated\r\nwith risk of adult onset asthma. In addition, no significant interaction was observed between age at menarche or\r\nmenstrual characteristics with body mass index or physical activity (in adolescence) in relation to adult onset asthma.\r\nConclusion: Early menarche is associated with a higher risk of developing adult onset asthma among reproductive\r\nage women. Mechanisms for this association are potential areas of future research.
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