The change in clock time disrupts sleep patterns, and this is known to reduce daytime alertness and increase the risk for having a stroke or heart attack; some studies also show a spike in the number of suicides. The body’s internal clock, or circadian rhythm, is strongly influenced by the amount of time that it is exposed to natural light. When daylight saving time starts, we wake up in the darkness and have more light in the evenings. This can cause circadian misalignment, delaying the sleep/wake cycle.