Taking an hour's nap after lunch can keep your brain five years younger, according to a new study.

一项新研究指出，午饭后休息1小时可以使你的大脑年轻5岁。

But researchers found that a longer or shorter nap did not produce the same results.

不过研究人员发现，较长或较短的午睡时间，无法产生相同的效果。

The study involved around 3,000 Chinese adults over the age of 65 - with 60 per cent reporting that they had a nap after lunch ranging from 30 to 90 minutes.

这项研究涉及约3000名65岁以上的中国人--其中60%的参与者称午饭后会午睡30至90分钟。

Participants were given basic maths problems and memory tests to complete to assess their cognitive¹ ability.

参与研究的人被要求完成基础的数学题和记忆测试，以此评估他们的认知能力。

The research, published in Journal of the American Geriatrics Society, found that people who took an hour-long nap after lunch did better on the tests compared to the people who did not nap.

这项发表在《美国老年医学会会刊》上的研究发现，那些午饭后睡眠1小时的人成绩要比没有睡午觉的人好。

In fact, those who took shorter naps, longer naps or no naps at all showed decreases in their cognitive skills that were four to six times greater than those taking hour-long naps.

事实上，对于午睡时间更短、更长或者完全不午睡的人来说，他们的认知能力的下降幅度是午睡1小时的人下降幅度的4至6倍。

Dr Junxin Li, who led the research, said: 'These people also experienced about the same decline in their mental abilities that a five-year increase in age would be expected to cause. Cognitive function was significantly associated with napping. Comparisons showed that moderate nappers had better overall cognition than non-nappers or extended nappers.'

领导这项研究的李俊新博士表示：“这些人的心智能力也有同样的下降，其幅度相当于年龄增加了5岁。认知功能与午睡有着重要的关联。对比研究表明，适度午睡者比没有午睡或午睡时间过长的人整体认知能力更高。”