A college student who is working in northern Alaska during the summer reports that he or she has an increase in difficulty sleeping since moving north.During a pre-employment physical,the patient asks the health care provider what could be causing this.The health care provider suspects the sleep disturbance is most likely because of which factor?

A) Stress of the new job
B) Increased daylight hours in Northern Alaska
C) Physical demands of the new job
D) Change in diet

Northern Alaska has extended daylight hours.Light and temperature affect all circadian rhythms,including the sleep-wake cycle.The most familiar rhythm is the 24-hour,day-night cycle known as the diurnal or circadian rhythm.When the sleep-wake cycle becomes disrupted (e.g.,by working rotating shifts),other physiological functions change as well.Stress of the new job,physical demands of the new job,and a change in diet are not the issues.The patient stated that the difficulty started when he or she moved north.