The study, published in Frontiers in Human Neuroscience journal, underscores the importance of sleep in maintaining good cognitive functioning.

The study divided participants in two categories: younger adults (18-37 years) and older adults (56-76 years). The participants were given wearable accelerometers to measure sleep duration and quality over seven nights.

"The night-to-night variability in older adults had a major impact on their performance in tests aimed at evaluating episodic memory," said Audrey Duarte, Associate Professor at the Georgia Institute of Technology, the US.

Stating that the association between sleep and memory has been known, Duarte said this study underlined the connection particularly among older adults and black participants.

"We wanted to know how sleep affected memory, how well they remembered things and how well their brains functioned depending on how well they slept," said Emily Hokett, a Ph.D student at the institute.

The researchers said regular sleep was important for best cognitive performance at any age.