December 16, 2024, 3:08 pm | Read time: 4 minutes

The recommendations are clear: sufficient exercise and sleep are important for good health, while daily sitting time should be kept to a minimum. A study has now clarified exactly what the ratio should be.

Wearing an Accelerometer

For the study, the researchers recruited 76 people over the age of 50 who lived in the UK and did not yet exhibit cognitive impairment^.2 All were part of a previous longitudinal micro-validation study aimed at assessing the equivalence between two brands of wrist-worn accelerometers. Participants wore the device on their dominant wrist for 24 hours over eight consecutive days. This allowed values for physical activity in the form of sport, sitting time, and sleep to be determined and then compared with cognitive performance using tests.

Evaluation of Sleep

Based on the previous assumption that the total sleep duration, the REM, and deep sleep phases are linked to cognitive performance, the scientists used precisely these values, which were provided by wearing the accelerometer. The total sleep duration was divided into short (two to six hours) and optimal (six or more hours).

Cognitive Tests

In addition, the participants completed cognitive tests on an online platform at the same time each day. The system always alternated between set A and set B in a random order to reduce the learning effect. The following areas were analyzed:

• Attention was assessed using an annulment test. In this test, the participants selected the occurrence of a certain symbol in a continuous row.
• Memory ability was analyzed using the so-called Corsi block tapping test. In this test, squares were highlighted in ascending order from two to nine. The test subjects were asked to memorize and reproduce these.
• Psychomotor speed was determined using a reaction test. The participants had to react as quickly as possible to a stimulus, with the time measured in milliseconds.
• The scientists gained an impression of executive function by means of a trail-making test. Here, the participants were asked to click on numbers and letters in ascending order as quickly as possible. The accuracy and overall time (processing speed) were then assessed.

Physical Activity Influences Cognitive Performance the Next Day

The analyses showed that the time spent the previous day with physical activity and little sitting time is linked to cognitive scores – especially episodic memory and working memory. 30 minutes of activity led to an increase of two to five percent the following day, provided that people maintained an optimal sleep duration of six or more hours. Each 30-minute increase in physical activity on the previous day led to an improvement in psychomotor speed performance.

For sleep, it was found that those who slept six or more hours the previous night had higher episodic memory and psychomotor speed scores. Each additional 30 minutes of REM sleep was associated with an increase in attention scores. Each 30-minute increase in deep sleep improved episodic memory ability and attention the following day.

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Classification of the Study

The study shows that sufficient sleep and physical activity can have a positive effect on cognitive performance from as little as 30 minutes. As a result, this could even reduce the risk of dementia. However, it should be noted that the research was only carried out on 76 people aged 50 and over in the UK. This may mean that the results are not transferable to the general public or to other age and population groups. Additionally, the precision of the analyses conducted with the activity trackers remains unclear.