Transcript for Could 'morning people' have a lower risk of breast cancer?
Now to a "Gma" health alert. New research about breast cancer and how sleep and the time you wake up could possibly affect your risk. Dr. Jennifer Ashton is here with us and I'll start with a question, Dr. Jen, for the audience, how many people here would consider themselves morning people? Okay. You're here at "Gma." Finally good news for the people who work on this show. Exactly. Thankfully we have you here with us. I've become a morning person out of necessity given my job but tell us a little about what this breast cancer and sleep study means for morning people and those who aren't. Well, this was an incredibly interesting study, Amy, because first of all you hear us say we have to be careful when we hear data or new headlines based on association. This study actually looked for an observation and association and then tried to prove causality, cause and effect. What they did, they looked at people's -- we call it crone know type. I had never heard that type before. Whether you describe yourself as a morning person or evening person. It didn't cite hours with that. Then it identified how many went on to develop breast cancer and then it did genetic analysis on those people. That's where they tried to prove cause and effect and what they showed was a protective effect amongst people who describe themselves as morning people. They had a lower risk of going on to develop breast cancer. Now here are my caveats with this. When we hear a study like this or a headline, we only hear one outcome. As a doctor, as a person, we have to think holistically, not just by body part so while it might be protective against breast cancer to be a morning person maybe we'll find it's bad against another outcome. Take it with a little grain of salt. Given left to my own devices I would be a night person for sure. I've heard that about you. This job just makes me keep waking up early. It might be good for me, Jen. Researchers also found -- interesting, this isn't necessarily new sleeping more than eight hours actually isn't good for you as well. That's right. Leads to a higher risk of breast cancer. If you slept more than seven or eight hours on average a night those people had an associated increase risk of developing breast cancer so when I say it's not new, it's because we have known for awhile especially in the world of sleep medicine that too much is not more is not better when it comes to sleep so that sweet spot is really about seven to nine hours a night for most people. For most health outcomes. Saying I get 11 hours a night that's not great. What happens when we sleep circadian rhythms get involved, inflammation, all kind of delicately balanced. You say seven to nine hours is optimal. What other sleep habits should we look at to decrease our jinx. You've heard me say it before. Sleep has a massive pr problem in this country. We look at it as a luxury. We need to prioritize it. You have to have a consistent bedtime and wake-up time. You can't just do one thing during the week and another thing on the weekends. Ruh-roh. Exactly. I cannot overstate that should be cold, dark and quiet and if you do those things I promise you you will feel better after a certain amount of time this. Is really the mainstay of our health foundation along with nutrition and fitness. We got -- Et cetera we'll go right back to bed. All right.
This transcript has been automatically generated and may not be 100% accurate.