It’s common for older people to say they have trouble sleeping.
老年人说自己睡眠不佳是常见的事。
There seem to be two main difficulties: falling asleep at the start of the night and then waking up too early in the morning – yet finding it impossible to get back to sleep.
这大概体现在两个方面：一入夜就睡着了，早上很早起来——然后再想继续睡似乎不可能。
In some cases, the discomfort caused by a medical condition exacerbates sleep difficulties, but many find that even without the disturbance of physical symptoms, sleep still eludes them for at least part of the night.
在一些情况下，医学病症加重睡眠困难，但很多人发现即使没有受到躯体症状的干扰，睡眠至少在夜晚的某个时段遇到困扰他们。
In a new study from Russia, 130 people went to a laboratory one morning and then stayed there all day and overnight. Staff kept them awake for the entire time, regularly asking them to assess how sleepy they felt.
在俄罗斯的一项新研究里，130人于早上去实验室，在那里呆了整天整夜。工作人员让他们一直保持清醒，并有规律地要求他们评估犯困的感觉。
These feelings of sleepiness vary throughout the day and night and in sleep deprivation experiments such as this, they are taken to reflect processes related to the body clock such as changes in body temperature at different times of day and the release of the hormone melatonin in the evening.
嗜睡的感觉在该睡眠剥夺实验的整个白天和晚上都有所不同，这些感觉被记录下来，它反应了人体生物钟的运动过程，比如在一天的不同时间内体温的变化和夜间褪黑激素的释放。
The slow-wave activity in the volunteers’ brains was also measured several times during the day and night.
志愿者的大脑慢波活动同样在白天和晚上多次被测量。
Then all this data was analysed in relation to a sleep diary the people had kept for the previous week, in order to see how the pattern of sleepiness and slow brainwaves varied according to propensity to be morning or evening types.
所有的数据与这些人在前一周的睡眠日记相比较进行分析，以了解嗜睡模式和缓慢脑电波是如何在早上和晚上变化的。
They found that, once again, the older people felt sleepy at different times from the younger people and had different timings of slow-wave activity in the brain.
他们再次发现，老年人与年轻人在不同的时间犯困，并且大脑慢波活动的时段也不同。
The study’s author, Arcady Putilov, suggests that two mechanisms might be responsible for the decrease in sleep time.
该研究的作者Arcady Putilov认为这两个因素可能是睡眠时间减少的原因。
He believes that in middle age the processes underlying the oscillations of slow-wave sleep weaken, making it harder to stay asleep, and on top of that, in older age the stronger circadian rhythms weaken because changes in body temperature and the release of the hormone melatonin weaken.
他认为中年人的慢波睡眠的振荡的潜在过程变弱，这使得保持睡眠更加困难，加之，由于体温变化和褪黑激素释放变弱，年纪越大，生理节奏则越弱。
