A good night's sleep is the secret to a sharp and alert mind. But the ideal duration to keep your brain healthy is often debated as too much or too little sleep can both impact cognitive health.

A new study published in Nature Mental Health delves deep into the sleeping patterns of people and finds out the most damaging ones that can destroy brain health and make one susceptible to conditions like Alzheimer's disease.

Scientists at the University of Warwick citing recent research urge adults to get around seven hours of sleep every night for optimal brain health..

They also found out the impact of sleeping longer than seven hours and this may be a warning for people who spend some extra hours on bed in the morning, lazing around and hitting the snooze button.

Researchers said people who sleep more than seven hours every day may suffer cognitive decline and diseases such as Alzheimer's.

However, sleeping less than seven hours could put people at risk of depression, heart disease and obesity.

The study led by Professor Jianfeng Feng from the School of Computer Science at the University of Warwick, analysed the sleep data of almost half a million adults in the UK aged between 38 and 73.

The data was categorized into two categories - one belonging to the 'short sleepers' while other to the 'long sleepers', representing people who slept fewer than seven hours and those that slept more respectively.

A surprising discoveryAfter analysing the data, it was found that the habit of having a 'lie-in' was linked with diseases such as Alzheimer's and schizophrenia. They also noted that hitting the snooze appears to be a symptom, rather than a cause, of these conditions. People who slept longer than required showed signs of cognitive decline, had higher inflammation and lower levels of 'good' cholesterol, which helps in elimination of dangerous cholesterol.

Long sleepers also showed brain matter loss in areas associated with memory and known risk areas for degenerative disease, such as Alzheimer's.

What about those who slept less?People who slept for less than seven hours were at an increased risk of low mood, fatigue and conditions like depression, heart disease and obesity. Their muscle and bone health was compromised and they also had vitamin deficiencies like vitamin D.