Abstract P6-12-02: Racial/ethnic differences in sleep quality and duration among breast cancer survivors: Results from the women's health initiative (WHI)
Authors: Beverly CM , Naughton M , Foraker R , Pennell M , Young G , Hale L , Crane T , Pan K , Danhauer S , Feliciano E , Paskett E 
Published: February 2018

BACKGROUND: Sleep is a crucial factor for optimal health, but breast cancer survivors often report poor sleep quality. It is estimated 20-70% of survivors have at least one sleep problem, which contribute to quality of life and health differences among survivors. Minority groups tend to have poorer sleep quality and shorter sleep duration than Non-Hispanic Whites (NHW). African-Americans (AA) with breast cancer have a poorer prognosis than NHW for each stage-specific diagnosis and are twice as likely as NHW to report short sleep duration, yet survivor studies are still lacking in AA participants. The purpose of this study was to examine sleep quality and duration patterns before and after cancer diagnosis by race/ethnicity among WHI breast cancer survivors.

METHODS: There were 12,098 postmenopausal women diagnosed with invasive breast cancer after WHI enrollment who were eligible for this secondary analysis. Baseline demographic and clinical characteristics were described. The WHI Insomnia Rating Scale (WHIIRS) was measured at multiple time points pre- and post-diagnosis. A higher WHIIRS scores (0-20 points) indicates greater sleep disturbance and ≥9 points identifies clinical insomnia. A linear mixed model was fit to the WHIIRS sleep quality data to examine if the trend in sleep quality with time changed following a cancer diagnosis. For short (&lt;6hrs) and long (≥9hrs) sleep duration, we fit a logistic regression model with multilevel mixed effects.

RESULTS: The majority of participants were NHW (87.4%), mean age at diagnosis was 70.3 years, and 75% had localized breast cancer at diagnosis. At baseline, 30% of women had insomnia. The lowest average WHIIRS score was 5.6 among Asians, and the highest was 6.6 among American-Indians and NHWs (p=0.02). AAs had the most women sleeping ≤5 hrs/night and NHW had the least (19.6% vs 5.7%, p&lt;0.01). At diagnosis, the average WHIIRS score was 7.2. After diagnosis, sleep quality improved in the overall study population (p=0.03). Short sleep duration ranged from 6% before diagnosis, 9% at diagnosis and 11% after diagnosis (p=0.29). Long sleep duration ranged from 3% before diagnosis, 6% at diagnosis and 15% after diagnosis (p=0.43). There was no difference in sleep quality across race after diagnosis (p=0.53). The probability of short sleep and long sleep after diagnosis did not differ significantly across race (p=0.12, p=0.90), however racial minorities tended to have higher probabilities of short sleep at diagnosis compared to NHWs.

DISCUSSION: Sleep is an appealing area to target for improvement due to the multiple ways it can be treated. With increasing survival rates, there is an emphasis on improving quality of life in survivors. Our results span 20 years pre-diagnosis to 15 years post-diagnosis and are similar to shorter follow-up studies which found most women's sleep problems resolve within a few years of treatment completion. The lack of difference by race was an unexpected finding in another similar longitudinal study, which suggested most differences are seen in cross-sectional sleep studies. This study adds to the literature on longitudinal sleep data, especially to the little data on sleep trajectories in minority breast cancer survivors.

Citation Format: Beverly CM, Naughton M, Foraker R, Pennell M, Young G, Hale L, Crane T, Pan K, Danhauer S, Feliciano E, Paskett E. Racial/ethnic differences in sleep quality and duration among breast cancer survivors: Results from the women's health initiative (WHI) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-12-02.