Participants wore a wrist actigraph for 72 consecutive hours at baseline (pre-chemotherapy), as well as during the first, second and third weeks of both cycle one and cycle four of chemotherapy. At each assessment they also completed a sleep log to record their bedtime, wake time and napping periods. Sleep-wake circadian activity variables were computed based on actigraphic data. Of the participants, 75 percent were Caucasian, 69 percent were married, 77 percent had at least some college education, and 73 percent reported an annual income of more than $30,000.

Compared with baseline measures, all circadian rhythm variables except acrophase (the time of day of the peak of the curve) were significantly impaired during the first week of both the first and fourth chemotherapy cycles. These circadian rhythm variables included amplitude (height of the circadian rhythm), mesor (the mean of the rhythm), up-mesor (time of day when activity was switched from low to high), and down-mesor (time of day when activity switched from high to low).

According to the study, further research must be conducted in order to better understand the mechanisms through which chemotherapy may contribute to impairments in sleep-wake activity. Potential mechanisms include psychological factors (i.e. anxiety and depression) and behavioral factors (increased daytime napping), as well as physiological factors and physical symptoms, such as decreased levels of estrogen, impaired cortisol responses and inflammation.

The authors state that it is important to screen more routinely for sleep and circadian disruptions in breast cancer patients undergoing chemotherapy and to offer appropriate management, such as cognitive behavioral therapy or bright light therapy, in order to prevent sleep disturbances from becoming chronic.

Source: American Academy of Sleep Medicine