While an afternoon nap may pep you up in the short-term, over time the indulgence could increase the likelihood of a premature death by almost a third, scientists claim.

Those who doze for an hour or more in the day may be putting themselves at risk of developing lung diseases including bronchitis, emphysema and pneumonia, the Daily Mail reported.

However, an academic not linked to the study have stressed that the figures show the majority of people will see no adverse affects from napping.

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Adults who nap every day are two-and-a-half times more likely to die from respiratory illnesses than those who only sleep at night, because napping can cause inflammation in the body, according to researchers.

The study published in the 'American Journal of Epidemiology' also suggests that needing to take a nap could itself be a sign that a person already has a lung disease.

To make their findings, researchers at Cambridge University tracked the lifestyles of 16,000 British adults who had agreed to be a part of a major research project into the causes of cancer over a 13-year period.

As part of the project, participants fed back information on their sleeping habits to researchers, including whether they napped during the day.

After analysing the data, scientists discovered that people who slept for less than an hour in the day increased the chance of death by around 14 per cent. This number rose to 32 per cent if the nap lasted for more than an hour, and was linked to the development of respiratory illnesses, according to the study.

Professor Jim Horne, from the Sleep Research Centre at Loughborough University, told the Daily Mail that most people are not at risk from napping.

"The findings actually show that the great majority – about 85 per cent – of those people who napped less than one hour were at no greater risk."

He added it is possible that the people who took part in the research and had serious and incurable lung illnesses might have benefited from their naps. "[Napping] may not have hastened death but delayed it" he told the newspaper.