London, July 23 (IANS) Babies cost parents as much as six months sleep in the first two years after their birth.

A survey among 1,000 parents has shown that on an average parents get just about four hours of uninterrupted sleep at night, which is an hour less than the minimum they require.

Two in three respondents said they had only three and three-quarters hours of sleep in one go, the Daily Express reported Friday.

There were also those who lamented that they had less than two-and-a-half hours of uninterrupted sleep.

The Express quoted Iftikhar Mirza, a sleep expert who commissioned the poll for mattress firm Silentnight, as saying: "What parents don’t realise is that it’s the lack of ‘basal’ sleep that’s the problem.

"You need a minimum of five hours uninterrupted sleep in one go. An hour here and there doesn’t negate ‘sleep debt’. Parents can eat healthily to boost immune systems and take regular, gentle exercise to release endorphins, which should lower the risk of mood swings."