Watching five hours of TV a day increases risk of dementia by nearly 50 per cent, study finds

Watching too much television increases the risk of dementia, academics have discovered.

People who watched more than five hours of TV a day had a 44 per cent greater risk of developing the debilitating condition, says a study of 400,000 people in the UK.

It was also associated with higher rates of stroke and Parkinson's disease, with up to three hours of TV a day found to be best for brain health. Researchers said the findings 'suggest high TV viewing time is associated with increased risk of various brain-related disorders'.

They analysed data on 407,000 people aged 37 to 73 from the UK Biobank project – with 40,000 of them having had a brain scan. None had any diagnosed brain disorder at the start of the study.

During the 13-year follow-up period, 5,227 developed dementia, 6,822 had a stroke and 2,308 were diagnosed with Parkinson's.

Academics have discovered people who watched more than five hours of TV a day have a 44 per cent greater risk of developing dementia (stock image)

Watching more than 5 hours of TV per day was associated with smaller memory centres (file)

The participants watched TV for 2.7 hours a day on average. 

Three to five hours was associated with a 15 per cent higher risk of developing dementia, compared to those who watched for one hour or less.

For those who watched more than five hours, it was 44 per cent higher, plus a 12 per cent increased risk of stroke and a 28 per cent greater risk of Parkinson's. 

No increased risk was found for time spent on computers, probably because such screen use is associated with more 'mentally challenging behaviour'.

The team from Tianjin Medical University, China, also found more than five hours of TV was associated with less grey matter and smaller memory centres, both of which are linked to brain diseases.

But exactly how watching TV has such effects is unclear. 

One theory is that sedentary behaviour, with low levels of muscle activity and energy expenditure, leads to chronic inflammation and reduced blood flow to the brain.

Reacting to the findings in the Journal of the America Medical Directors Association, James Rowe, professor of cognitive neurology at Cambridge, said: 'A couple of hours did not increase the risk. So, enjoy your favourite TV, then go and do something else.'

How cards can curb joint pain - hands down! 

Playing poker or gin rummy not only keeps the mind active – it can also help our joints stay supple as we age, research has shown.

And these benefits apply to other games too, such as chess and mahjong, due to the repetitive arm movements involved.

Researchers from Shanghai University School of Medicine found that actions such as dealing cards ‘provide passive exercise’.

They explained: ‘These movements can help sustain range of motion and lubrication of the shoulder joint.’

Of the 8,000 people who took part in the study, published in the journal Experimental Gerontology, those who played games were 40 less likely to have shoulder pain.