Night Sleep Duration and Risk of Incident Anemia in a Chinese Population: A Prospective Cohort Study

The purpose was to study the association between sleep duration and the prevalence of anemia in Chinese people. There were 84,791 participants (men: 79.1%; women: 20.9%) aged 18-98 years in the prospective study. We divided the participants into five categories based on the individual sleep duration: <= 5 h, 6 h, 7 h(reference), 8 h, and >= 9 h. Anemia was defined based on hemoglobin <12 g/dL for men and <11 g/dL for women. The Cox proportional hazards model was used to assess the association between sleep duration and anemia. During median follow-up of 7.9 years, 2698 cases of anemia had occurred. The HRand (95% CI) of anemia (7 h as the reference group) for individuals reporting <= 5 h, 6 h, 8 h, and >= 9 h were 1.23(1.04-1.45), 1.26(1.11-1.44), 1.04(0.92-1.16) and 1.42(1.08-1.86), respectively. It showed that there was a significant interaction on the risk of anemia between sleep duration and sex in the secondary analysis (p < 0.001). The significant association between long sleepduration and anemia was found in women (HR, 2.29; 95% CI, 1.56-3.37), not in men(HR, 0.90; 95% CI, 0.60-1.34). Both short and long night sleep duration were associated with increased risk of anemia.