Table 1 Descriptions of the 24-hour rest-activity rhythm metrics used in this study

Mesor (Midline estimating statistic of rhythm)

Mean level of activity over the 24-hour period

A person with a higher mesor has recorded more average activity across the 24-hour period than someone with a lower mesor

Amplitude

Difference between the peak activity level and minimum activity level

A person with a higher amplitude has recorded more overall maximum activity relative to their minimum activity and has higher overall rhythmicity (more rhythmic changes) than someone with a lower amplitude

Acrophase

Timing of peak activity in the 24-hour period

A person’s peak activity occurs later in the 24-hour period when acrophase is at a later time than someone with an earlier acrophase. Later acrophase may reflect a more delayed activity phase in the 24-hour period.

Inter-daily stability (IS)

Day-to-day variability of the 24-hour rest-activity rhythm

A person with consistent daily rest-activity rhythms over consecutive days has a higher IS than someone with a weaker adherence to the circadian rhythm between days.

Intra-daily variability (IV)

Within-day fragmentation of the 24-hour rest-activity rhythm and transitions between rest and activity

A person with a lower IV has a relatively stronger rest-activity rhythm (e.g., better sleep efficiency, lower fragmentation of rest-activity rhythms) than someone with higher IV.

M10

Mean activity level during the most active 10-hours of the 24-hour period

A person with a higher M10 would average more activity during waking hours than someone with a lower M10 value.

L5

Mean activity level during the least active 5-hours of the 24-hour period

A person with a lower L5 would average less activity during resting (usually nocturnal) hours than someone with a higher L5 value. A higher L5 is reflective of less restful sleep.