While a number of studies have been undertaken previously on the importance of sleep, no study has given clear insight into the correlation of sleep duration to cognitive performance. This new study gives a detailed view of this correlation which is quite exciting.

The researchers designed a set of twelve special tests to evaluate cognitive performance and developed an online portal where a thorough demographic questionnaire was put up. Participants were asked to complete the questionnaire along with the estimated sleep duration the previous night and take the twelve tests.  Incomplete submissions were discarded and finally, the data of over 10,000 candidates was collected and analyzed.

Half of the candidates reported 6.3 hours or less of sleep at night. Interestingly, the results of the cognitive tests reflected a U shape. Candidates who slept less than the seven hours performed worse on the cognitive tests for reasoning and verbal abilities than the candidates who slept for the required number of hours (7-8 hours of sleep at night). Similarly, candidates who slept for more than 8 hours also performed worse than those who got the recommended 7-8 hours of sleep.

“We found that the optimum amount of sleep to keep your brain performing its best is seven to eight hours every night and that corresponds to what the doctors will tell you need to keep your body in tip-top shape, as well,”

Conor Wild, lead author on the study said.

“We also found that people that slept more than that amount were equally impaired as those who slept too little.”


Between seven to eight hours of sleep is recommended for optimal cognitive performance
Credit: belchonock/Depositphotos

Interestingly, it was found that oversleeping or undersleeping didn’t affect all kinds of cognitive performance. While reasoning and verbal abilities were affected quite a lot, short-term memory remained somewhat unaffected by short sleep duration, even going as low as four hours.

Thus, the study suggests that higher-order cognitive processes are most affected by bad sleeping habits. While previous studies have shown that complete sleep deprivation can adversely affect short and long-term memory, this study shows that these effects can be mitigated by sleep as little as four hours. More complex cognitive functions, such as problem-solving, however, require longer and more consistent sleep hours.

While more studies are required to ascertain why these effects are exhibited, this study at least corroborates the claim that 7-8 hours of sleep is ideal.