Gender, bipolar subtype influence susceptibility to mood disturbances following sleep loss
Sleep loss may trigger mania or high mood episode in about one in four individuals with bipolar disorder, and this vulnerability is particularly pronounced among women or those with bipolar disorder type I (BP-I), a study suggests.
During a semistructured interview of 3,140 individuals with a lifetime diagnosis of affective disorder, it was found that the tendency for mood episodes to occur as triggered by sleep loss differed by gender and bipolar subtype. [Br J Psychiatry 2017;doi:10.1192/bjp.bp.117.202259]
Specifically, episodes of sleep loss-triggered high mood were more likely reported by women vs men (21.7 vs 16.3 percent; adjusted odds ratio [aOR], 1.30; 95 percent CI, 1.05 to 1.61; p<0.015) and by those with BD-I vs BD-II subtype (24.7 vs 10.8 percent; aOR, 2.81; 2.23 to 3.53; p<0.001).
Reports of sleep loss-triggered depression, on the other hand, were more common among women vs men (12.7 vs 9.5 percent; aOR, 1.29; 0.99 to 1.68; p=0.06) and among those with BD-II vs BD-I subtype (13.6 vs 10.7 percent; crude OR, 1.25; 0.99 to 1.57; p=0.054), although the results were not significant.
Of the individuals included in the study, 2,146 were women (68 percent) and 2,075 had BD-I (66 percent). The mean age at interview was 46.4 years.
The differences observed in the tendency for sleep loss to trigger high mood potentially reflect clinical and underlying neuroanatomical differences between BD-I and BD-II subtypes, the authors noted.
Although it could be possible that fewer individuals with BD-II reported sleep loss-triggered mania because they were generally less able to identify episode triggers, “one of the proposed mechanisms by which sleep loss affects emotion regulation is by disrupting emotion regulation systems in the brain (eg, prefrontal and limbic areas), and recent neuroimaging studies have found that these same neurological systems vary between BD-I and BD-II and correspond with behavioural differences in emotion regulation,” they explained. [Am J Psychiatry 2013;170:533-41; Int J Psychophysiol 2013;89:218-28; Bipolar Discord 2015;17:461-70]
With respect to the gender difference, the present data are in agreement with previous studies reporting that women appear to be at greater risk than men of mood disorders following sleep loss. This partly explains why women with bipolar disorder are likely to experience mania following childbirth, which is a life event associated with sleep deprivation, the authors pointed out. [Sleep Med 2015;16:987-93; J Affect Discord 2015;180:90-96; Lancet 2014;384:1789-99]
“These gender differences provide interesting avenues to explore underlying mechanisms by which gender and sleep may interact to influence bipolar disorder phenotypes [eg, ovarian hormones may interact with the circadian system to affect the sleep-wake cycle and responses to sleep deprivation],” they added. [Front Neuroendocrinol 2014;35:111-39]
The authors pointed out that despite the presence of limitations including the retrospective nature of the data and the potential impact of the bidirectional relationship between sleep and mood on evaluating whether sleep loss had been a trigger or prodrome of episodes, the present study highlights the importance that clinicians discuss with bipolar disorder patients the weight of sleep loss as a trigger.
Patients should be encouraged to keep a regular sleep pattern and consider the potential impact of specific situations such as shift work and long-haul travel, the authors said.