Leveraging Sleep Quality to Optimise How We Work

There is robust scientific evidence demonstrating that impaired sleep significantly affects cognitive function but the scientific evidence on the relationship between experienced subjective sleep quality and cognition is still inconclusive.

The majority of studies are also focussed on those engaged in safety critical outcomes rather than those engaged in broader office based roles where performance is also linked to cognitive function (knowledge workers).

We hypothesised that objective measurements of Total Sleep, Deep Sleep and REM hours, as well as a subjective measurements of self-reported sleep quality were all predictors of how well knowledge workers would perform cognitively the following day.

The study involved tracking 144 men and women from a cross-section of knowledge worker industries for a period of 14 consecutive days. Each person wore a Fitbit smartwatch to track their sleep and each morning they also captured a subjective measure of how well they felt they had slept on a 5 point scale from 'Terribly' to 'Great'.

Each person captured a relative score of their cognitive function in the OwnLife app 4 times per day at equal, 4-hour intervals. Scores were captured across 4 cognitive domains: Mental Clarity (cf Working Memory), Mental Focus (cf Attention), Mental Stability (cf Cognitive Flexibility) and Mental Energy (cf Processing Speed).

Data were analysed using an Analysis of Variance (ANOVA) to determine how significant sleep factors were in their effect on each cognitive domain.

For the average knowledge worker, by definition because they think for a living, their performance at work is related to their level of cognitive function.

One implication is that given sleep significantly affects cognitive function the next day, for the average knowledge worker, actively managing sleep factors is an important consideration when it comes to optimising personal productivity at work, i.e. by prioritising sleep we can improve our productivity and effectively create more time for ourselves.

As this study has also demonstrated, even without wearing a sleep tracker, subjective self-reported sleep quality is a very significant predictor of our cognitive function and hence productivity the following day.

The implication of this is that just by taking note of how well we felt we slept when we wake up, we are able to tell how well we are going to function that day and therefore have the ability to actively manage what we work on that day, based on our capability.

We know that if we slept really well we should be taking on the really cognitively demanding and challenging things on or to-do lists, and that if we slept badly, where possible, we should focus on less complex tasks.

Without even changing how we sleep, this simple process of actively changing what we work on based on how we have slept, and balancing our workload based on our predicted level of cognitive function, can have an important effect on our productivity.

Our research also demonstrates that cognitive function declines significantly through the course of the working day, and we know from the above study that this is related to subjective sleep quality. After a 'Great' night's sleep, cognitive function is stable throughout the day, but after a 'Bad' or 'Terrible' night's sleep, cognitive function is significantly more variable (especially Mental Clarity & Mental Focus).

We aim to publish our research on more individualised sleep optimisation in due course.