Fig. 2. Relative risk (RR) and 95% confidence interval (CI) of incident coronary heart disease (CHD) according to age at menarche. RRs (hazard ratios) are stratified by region of recruitment and adjusted for year of birth, body mass index, height, smoking, alcohol consumption, exercise, and socioeconomic status. The reference category is menarche at 13 years of age. The area of the square is inversely proportional to the variance of the log risk. ICD-10, International Classification of Diseases, 10th revision. Adapted from Canoy et al. Circulation 2015;131:237-44, with the permission of Wolters Kluwer Health, Inc.7).
