Sofie Lieberoth1, Elisabeth Gade1, Kirsten Ohm Kyvik2, Vibeke Backer1, Simon Francis Thomsen3. 1. Department of Respiratory Medicine, Bispebjerg Hospital, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark. 2. Institute of Regional Health Services Research, Odense Patient Data Explorative Network & The Danish Twin Registry, University of Southern Denmark, DK-5000 Odense C, Denmark. 3. Department of Respiratory Medicine, Bispebjerg Hospital, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark. Electronic address: simonfrancisthomsen@gmail.com.
Abstract
AIM: To examine the association between early menarche and risk of post-menarcheal asthma. METHODS: Using data from two multidisciplinary questionnaire surveys, conducted eight years apart, we prospectively studied 10,648 female twins, 12-41 years of age, from the nationwide Danish Twin Registry. Early menarche was defined as menarche before 12 years of age. We performed a cohort analysis and a co-twin control analysis including twin pairs discordant for incident asthma. RESULTS: Early menarche was observed in 9.3% of the individuals. The eight-year cumulative incidence of asthma was higher in girls with early menarche compared to girls without early menarche (7.4 vs. 4.5%), OR = 1.71 (1.31-2.22), p < 0.001; also after adjustment for BMI, current age, physical activity, education, and smoking, OR = 1.53 (1.15-2.04), p = 0.003. The unadjusted risk of asthma was increased by 8% (1-15%), p = 0.041 per year earlier menarche occurred. Among 167 twin pairs discordant for incident asthma, there was a non-significant tendency towards early menarche being more common in the asthmatic than the non-asthmatic co-twin (12.0 vs. 9.6%), OR = 1.57 (0.61-4.05), p = 0.350. The risk of asthma was not uniform in discordant monozygotic and dizygotic twins. CONCLUSION: Early menarche is associated with increased risk of asthma among Danish female twins independently of BMI, age, physical activity, educational level and smoking. Results indicate a complex relationship possibly mediated through innate and non-genetic effects.
AIM: To examine the association between early menarche and risk of post-menarcheal asthma. METHODS: Using data from two multidisciplinary questionnaire surveys, conducted eight years apart, we prospectively studied 10,648 female twins, 12-41 years of age, from the nationwide Danish Twin Registry. Early menarche was defined as menarche before 12 years of age. We performed a cohort analysis and a co-twin control analysis including twin pairs discordant for incident asthma. RESULTS: Early menarche was observed in 9.3% of the individuals. The eight-year cumulative incidence of asthma was higher in girls with early menarche compared to girls without early menarche (7.4 vs. 4.5%), OR = 1.71 (1.31-2.22), p < 0.001; also after adjustment for BMI, current age, physical activity, education, and smoking, OR = 1.53 (1.15-2.04), p = 0.003. The unadjusted risk of asthma was increased by 8% (1-15%), p = 0.041 per year earlier menarche occurred. Among 167 twin pairs discordant for incident asthma, there was a non-significant tendency towards early menarche being more common in the asthmatic than the non-asthmatic co-twin (12.0 vs. 9.6%), OR = 1.57 (0.61-4.05), p = 0.350. The risk of asthma was not uniform in discordant monozygotic and dizygotic twins. CONCLUSION: Early menarche is associated with increased risk of asthma among Danish female twins independently of BMI, age, physical activity, educational level and smoking. Results indicate a complex relationship possibly mediated through innate and non-genetic effects.