Age distribution of SCD patients with CH. (A) Age distribution of patients with SCD, with and without CH. The mean age ± standard deviation of patients with SCD with and without CH was 42 ± 12 years and 23 ± 14 years, respectively. ****P < .0001, Student t test. (B) Prevalence of CH according to age with 95% confidence interval. Patients with SCD and African American controls without SCD are grouped by decade. The prevalence of CH in controls without SCD who were older than 70 years of age is shown in supplemental Figure 4B. Genes carrying the CH mutation in patients with SCD are shown for each age group. In the groups aged 20 to 29, 30 to 39, 40 to 49, 50 to 59, and 60 to 69 years, the percentage of patients with SCD and CH is 0.3%, 1.5%, 3.5%, 5.8%, and 9.1%, respectively, whereas the percentage of controls with CH is 0%, 0.1%, 1.6%, 2.8%, and 5.1%, respectively. N, number; NA, not applicable.