Why is the week after spring daylight savings time (DST) so rough? Research has shown the day following spring DST fatal car accidents increase by 6%. Productivity also goes down at work - less sleep is associated with decreased attention and alertness. Why? Because - circadian rhythms. Your brain, specifically the suprachiasmatic nucleus (SCN) regulates your body clock that helps you know when to be awake and when to go to sleep. This internal clock takes its cues from the s