Trajectories of sleep quality during the first three years after breast cancer diagnosis.

Objective: To identify trajectories of sleep quality up to three years after breast cancer diagnosis and to assess differences in characteristics of patients across distinct trajectories.

Methods: A total of 458 breast cancer patients underwent a neurological evaluation before treatment and at one and three years after diagnosis. Clinical data were obtained throughout the follow-up. Anxiety and depression were evaluated at baseline, using the Hospital Anxiety and Depression Scale. In all sessions of follow-up, sleep quality was assessed using the Pittsburgh Sleep Quality Index. Model-based clustering was used to identify groups of patients with homogeneous variation in sleep quality.

Results: We identified three trajectories of variation in sleep quality, named "low" (LSQ), "medium" (MSQ), and "high sleep quality" (HSQ). Women in the HSQ trajectory presented good sleep quality during the three years. LSQ and MSQ trajectories were characterized by poor sleep quality during the whole period, although during the first year the latter depicted a significant deterioration of sleep quality and the former a significant improvement. Patients included in the LSQ trajectory were more likely to have clinically significant anxiety and depression at baseline. The two trajectories with worse sleep quality were associated with neuropathic pain three years after cancer diagnosis.

Conclusions: This study provides a model for describing the variation in sleep quality during the first three years after breast cancer diagnosis, based on three main trajectories. Further studies are needed understanding the heterogeneity of the individual trajectories within each of these major patterns of variation.