Very old, Chinese and sleeping well

For my money, the paper of the week through my mailbox last week was a report about sleep habits in very old Chinese patients, which was published in Sleep journal at the start of May.

The report was an analysis of data collected in 2005 in the 'Chinese Longitudinal Healthy Longevity Survey' (CLHLS). The survey participants included over 15000 individuals over the age of 65. Most remarkably, there were over 2700 participants over 100 years old, making this an entirely unique dataset.

Unfortunately, only two question were asked about sleep in that survey - which didn't leave the researchers a hell of a lot to work with. ("How do you rate your sleep quality recently" and "How many hours on average do you sleep every day including napping?"). They did manage to look at the data every which way, and were able to evaluate the impact of other health problems and age itself on these two parameters.

Why is this interesting? Well, it used to be common wisdom that people sleep less as we get older. However, there have been studies demonstrating that once health problems are taken into account, there is no reduction in sleep time associated with increasing age in adults.

In this Chinese study, very old (over 100 years) Chinese tended more often to sleep 'too little or too much (my words; more sleeping less than 6 hours, and more sleeping more than 10 hours) when compared with younger old Chinese. Most of this was due to poorer health, which was significantly associated with poorer sleep quality and sleep hours outside of the 7-9 hour 'healthy sleep' window throughout all age groups. There was no significant variability in sleep duration between the age groups below 100 years. Between the ages of 65 and 100+ in this study there was no reduction in good sleep quality over the years. In fact, older participants (over 100 years) were more likely to have good sleep quality then younger participants when socioeconomic status, social support and health practice were controlled for.

These results seem to suggest that bad sleep is not necessarily a part of healthy ageing. The associated editorial in the journal suggest that the study demonstrates that, amongst the oldest old (over 80), age was a very strong predictor of good sleep quality. (I found it difficult to extract that much from the data - but surely the editorial couldn't be wrong). Could it be that 'good health predicts longer and better sleep, and longer and better sleep predicts good health'? Watch this space.

One statistic which you won't be hearing much about from doctors is that current smokers and alcohol users were, in contrast to other studies, more likely to have good sleep quality....

Andrew