Association between hemoglobin trajectories and the incidence of dementia in a cohort of females aged 55–79 years

Purpose: To assess the association between pattern changes in hemoglobin levels over time and the incidence of dementia using trajectories in females aged 55–79 years. Materials and methods: We conducted a retrospective cohort study using females of aged 55–79 years from the National Health Insurance Service National Health Screening Cohort in Korea. To identify hemoglobin trajectories over eight years (2002–2009), we performed a three-step approach comprising measures of change, factor analysis, and cluster analysis. Univariate and multivariate Cox proportional hazard models were used to assess the associations between hemoglobin trajectories and the incidence of dementia. Results: We included 20,195 of 235,742 female participants. New dementia (N = 2664) was developed during follow-up period (2010–2015). Five hemoglobin trajectories were identified: high, mid, low, increasing, and decreasing. With high as a reference, the hazard ratios (HRs) for low and decreasing trajectories were significant, 1.28 (95% confidence interval [CI], 1.13–1.45) and 1.21 (95% CI, 1.10–1.34) in univariate models, respectively. However, only the HR for the decreasing trajectory was significant, 1.12 (95% CI, 1.01–1.24) after adjustment for confounders. Conclusion: The decreasing trajectory of hemoglobin levels within the normal range was associated with dementia. Even females aged 55–79 years without anemia might be vulnerable to dementia development risk.