Polysomnographic Study of Sleep in Survivors of Breast Cancer

Abstract

Study objective: Insomnia is a frequent complaint in breast cancer patients during and after treatment. Breast cancer survivors, 1-10 years posttreatment, underwent in-lab polysomnography (PSG) to objectively define the insomnia in those patients with such a complaint.

Methods: Twenty-six breast cancer survivors (aged 39-80, mean 54.0 months posttreatment) spent 2 nights in the sleep laboratory. Sleep on Night 2 was scored for sleep stages, sleep onset latency, REM sleep onset latency, wake time, apneas and hypopneas, periodic limb movements and arousals. Subjects were allocated into 2 groups by their scores on the Pittsburgh Sleep Quality Index (PSQI): no/ mild sleep disturbance (PSQI score ≤ 9, n = 15) or moderate/ severe sleep disturbance (PSQI ≥ 10, n = 11).

Results: Standard PSG/EEG parameters failed to differentiate insomniacs from non-insomniacs. The single variable that distinguished the insomnia group was periodic limb movements in sleep (PLMS). PLMS were significantly correlated (r ≅ 0.7, p < 0.02) with subjective report of insomnia on PSQI and insomnia severity index. Log[Number of PLMS] was higher in the moderate/severe insomnia group (p = 0.008). Five of 11 patients in the moderate/severe insomnia group had a PLMS index ≥ 15, compared to only one of 15 patients in the none/mild insomnia group (p = 0.02). Menopausal symptoms and use of caffeine, hypnotics, and antidepressants were unrelated to insomnia severity or PLMS.

Conclusions: PLMS was the sole PSG variable that separated breast cancer survivors with moderate/severe insomnia from those with no/mild sleep disturbance. Further study of the incidence and significance of PLMS in breast cancer survivors with the complaint of insomnia is merited.

Keywords: breast cancer; cancer survivors; insomnia; periodic limb movements in sleep; sleep.

Figure 1. Histogram of PSQI scores.

Histogram of PSQI scores for the full sample of 26 patients, showing the division of patients into two groups by severity of insomnia using a cutoff score of 10 on the PSQI.

Figure 2. PLMS arousal index.

PLMS arousal index compared between patients with none/mild or moderate/severe insomnia as measured by the PSQI (using cutoff score of 10). A significant difference between groups is seen (p = 0.075 by t-test; p = 0.008 after log transformation).