The Anchorman star admits the sleep disorder has taken a toll on her "health, personality and well-being".

"It's something a lot of people don't talk about," the 45-year-old told People magazine. "Millions and millions of people aren't sleeping... It affects your spiritual self, emotional self and physical self."

Christina first started experiencing insomnia in her mid-20s and she admits the birth of her daughter Sadie Grace in 2011 really upset her sleep patterns.

"In my 20s and 30s, I used to never be able to fall asleep and would just stay up all night long," the actress explained, "but when my daughter was born, I got into a three-hour feeding cycle. Now she sleeps 10 hours a night, but my body still wakes up every few hours. I'll also be up from 2am to 6am and finally fall asleep. And then she (Sadie Grace) comes in and is ready for breakfast!"

Applegate tells the publication there are guidelines she follows in an effort to get a good night's sleep - these include keeping her bedroom at a chilly "60 to 68 degrees", adding, "It should never be any warmer than that", making sure TVs and cellphones are turned off, and even persuading her husband, Martyn LeNoble, to use a straw when he drinks water in the night.

"If you have water next to your bed and you have a partner, make sure to have straws, because they cut down the noise," she added. "My husband would have water in the middle of the night and that would wake me up with that gulping sound."

And the couple has a strict no pets allowed in the bedroom rule: "We love our pets, but we had to start not having them in the bedroom because we couldn't sleep. They would constantly roll around and move. It was the saddest thing."