Posttraumatic stress disorder (PTSD) is associated with disturbed sleep and elevated
levels of pro-inflammatory cytokines, including interleukin-6 (IL-6) and tumor necrosis
factor-α (TNF-α). Studies in animals and healthy humans have also shown that disrupted
sleep elevates pro-inflammatory cytokines, including IL-6 and TNF-α. A better understanding
of overnight cytokine levels and sleep might shed light on possible mechanisms for
elevated inflammation in PTSD. Thus, we investigated overnight levels of IL-6 and
TNF-α in individuals with and without PTSD while recording sleep polysomnography (PSG).
Serum samples were collected from otherwise healthy, medication-free participants
with chronic PTSD ( n =44; 50% female; M age=30.34± 8.11) and matched controls (
n =49; 53% female; M age=30.53± 6.57) during laboratory PSG. Levels of IL-6 and
TNF-α were measured at hours 0, 2, 4, 6, and 8 after typical sleep onset time using
serial serum samples. Plasma IL-6 and TNF-α levels were quantified using enzyme-linked
immunosorbent assays. Growth model analysis indicated a significant group by time
interaction for IL-6 ( t [247] = −2.92, p = .005) and a significant group by sex
by time interaction for TNF-α ( t [275] = 2.02, p = .04). PTSD positive men and
women initially had higher IL-6 and TNF-α at sleep onset, but not at the end of their
sleep cycle. Men with PTSD showed a peak of TNF-α at the end of the sleep cycle, whereas
male control subjects demonstrated an inverted U-shaped profile. There were no significant
differences in TNF-α levels overnight between women with and without PTSD. To our
knowledge, this is the largest study to examine IL-6 overnight in a PTSD sample and
the first study to examine overnight TNF-α in PTSD. Overnight IL-6 and TNF-α levels
may be altered in individuals with PTSD compared to those without PTSD, and TNF-α
trajectories also differed by sex. The current findings highlight the need to consider
sex, sleep, time of day, and circadian variation when examining inflammation in PTSD.
Additional research in broader study samples will be necessary to clarify associations
between disrupted sleep, cytokines, and increased risk for disease in PTSD.