In December 2018 researchers from the USA published the results of their study to assess whether night to night variability in sleep was associated with insomnia. 723 individuals kept a sleep diary for a period of 14 days and were then divided into four groups according to the presence/absence of a sleep complaint and presence/absence of poor sleep. Total sleep time, delay in sleep onset, wake after sleep onset, number of nightly awakenings, and sleep efficiency were then assessed. Results showed that poor sleepers appeared to have greater night-to-night variability in total sleep time, delay in sleep onset, wake-after-sleep onset, number of nightly awakenings, and sleep efficiency. A further analysis revealed that delay in sleep onset was significantly greater amongst poor sleepers who complained than poor sleepers with no complaints and that the number of nightly awakenings was significantly greater amongst good sleepers with complaints than good sleepers with no complaints.
Molzof HE et al. Intraindividual sleep variability and its association with insomnia identity and poor sleep. Sleep Med. 2018 Dec;52:58-66