The study was published in the August 2012 issue of Breast Cancer Research and Treatment. Read the abstract of “Association of sleep duration and breast cancer Oncotype DX recurrence score.”
The Oncotype DX test is a genomic test that analyzes the activity of a group of 21 genes that can affect how a cancer is likely to behave and respond to treatment. The test is done on a breast cancer tissue sample. The Oncotype DX test is used in two ways:
- to help doctors figure out a woman’s risk of early-stage, estrogen-receptor-positive breast cancer coming back, as well as how likely she is to benefit from chemotherapy after breast cancer surgery
- to help doctors figure out a woman’s risk of DCIS (ductal carcinoma in situ) coming back and/or the risk of a new invasive cancer developing in the same breast, as well as how likely she is to benefit from radiation therapy after DCIS surgery
Oncotype DX test results assign a Recurrence Score – a number between 0 and 100 – to the early-stage breast cancer or DCIS:
- Recurrence Score lower than 18 means the cancer or DCIS has a low risk of recurrence.
- Recurrence Score between 18 and 31 means the cancer or DCIS has an intermediate risk of recurrence.
- Recurrence Score greater than 31 means the cancer or DCIS has a high risk of recurrence.
While the Oncotype DX DCIS test uses the same range for recurrence scores — 0 to 100 — the scores are interpreted differently.
In this study, researchers reviewed the medical records of 101 women diagnosed with early-stage, estrogen-receptor-positive breast cancer. All the women had undergone Oncotype DX testing and had Recurrence Scores. The researchers also asked the women about how long they slept per night in the 2 years before they were diagnosed.
The researchers compared the Oncotype DX Recurrence Score for each woman to the average number of hours she slept per night. In postmenopausal women, they found that higher Recurrence Scores were linked to fewer hours of sleep per night:
- Postmenopausal women who slept 6 hours or fewer per night had higher Recurrence Scores compared to women who slept more hours per night.
This difference was statistically significant, which means that it was likely due to the difference in sleep time and not just to chance.
The average amount of sleep per night didn’t seem to affect recurrence risk in premenopausal women.
It’s not clear what may be causing the link between a lack of sleep and higher estrogen-receptor-positive breast cancer recurrence risk in postmenopausal women. Some doctors think that lower levels of melatonin, a hormone made in the brain, could explain the higher risk. Melatonin plays a role in regulating the body’s sleep cycle and may also help regulate cell growth and repair. People who don’t get enough sleep tend to have lower melatonin levels. Lower melatonin levels may lead to patterns of breast cell growth and repair that make breast cancer more likely to develop.
We also know that much of the repair of the everyday wear and tear of living on the body happens while we sleep. Sleep deprivation can cause low grade inflammation, which is linked to almost all types of cancer and heart disease.
In our 24-hour society, it can be hard to turn in, tune out, and unplug from everything, but there are steps you can take to get a good night’s sleep:
- Reserve your bed for two things only: sleep and sex. Don’t read, watch TV, talk on the phone, check your email, log into Facebook, or do work in bed.
- Maintain a regular sleep/wake schedule. Your body will get used to falling asleep and waking up at a specific time if you stick to a routine.
- Don’t nap, especially if you have trouble falling asleep.
- Avoid caffeine, alcohol, and heavy/spicy/sugary foods 4 to 6 hours before you go to bed. They can disrupt your sleep or upset your stomach.
- Exercise regularly – daily if you can – but not right before bed. Exercise in the morning or afternoon can help you sleep more deeply.
- Make your bedroom as comfortable as possible. Keep the bedroom at a comfortable temperature and block out all extra light.
To learn more about tips for good sleep, read our Ask-the-Expert Online Conference transcript: Sleep Well: Healthy Habits for Good Rest.