Kaplan-Meier survival curves for Chuvash polycythemia patients and spouses or community members matched for age, sex and place of birth. (A) Sixty-five patients with Chuvash polycythemia and 65 spouses. (B) Ninety-four patients with Chuvash polycythemia and 94 matched community members. There was high mortality for the community members in the first 3 years of life, whereas the median age of diagnosis of Chuvash polycythemia was 16 years. (C) Seventy-six patients with Chuvash polycythemia and 76 matched community members who survived to age 16 years.