Objectives: Transitions into and out of daylight saving time (DST) have been associated with altered rates of myocardial infarction, road traffic accidents, and impairments in mood and cognition; all of which have been attributed to changes in sleep duration/quality and circadian misalignment. In the present exploratory study we investigated the extent to which missed appointments at NHS hospital outpatient clinics varied according to transitions into and out of DST.
Methods: We assessed the percentage of missed appointments at hospital outpatient clinics in Scotland for individuals aged 18-64, during the two weeks before the clock change, the week of the clock change, and the two weeks after the clock change (for both transitions into and out of DST). Incidence ratios (IR) were computed for each weekday × year (2005-2010), for both forward (March) and backward (October) clock-changes, reflecting the % of missed appointments during the week of the clock change (observed) divided by a baseline measure encompassing the 2 weeks pre- and post-clock change (expected). IR > 1 indicates elevations in missed appointments; while IR < 1 indicates a relative decrease in missed appointments.
Results: Total number of appointments given out during the analysed weeks of interest equalled 1,004,641; of which 11.75% were missed. For the week of the spring clock-change, the only reliable change in missed appointments was found on the Thursday, with missed appointments increasing by approximately 6% (IR = 1.056, CI: 1.014-1.099). On the Monday during the autumn clock-change, missed appointments decreased by 8.5% (IR = 0.915, CI: 0.836-0.997). No other reliable weekday differences were observed.
Conclusions: Though preliminary, these modest alterations in the number of missed appointments may reflect changes into and out of DST, through the downstream effects of sleep and circadian disruption on cognition and behaviour. Novel ways of assessing how DST may impact behaviour at a societal level should be considered.