Fig. 3From: Preventing misdiagnosis of diabetes in the elderly: age-dependent HbA1c reference intervals derived from two population-based study cohortsSex-specific associations between age and HbA1c levels in the SHIP-0 and SHIP-Trend population. a) Linear regression analysis with restricted cubic splines (in case of significant likelihood ratio test, see method section) and b) estimated mean levels with 95% confidence interval assessed by analysis of variance (ANOVA). All models were adjusted for body mass index. The definition of healthy subjects is given in Fig. 1 and the regression estimates in Table 2Back to article page