US researchers have used neuroimaging to show that war veterans with poor sleep quality have reduced frontal lobe volumes.
The association between sleep quality and frontal lobe atrophy was independent of exposure to trauma and of psychiatric comorbidity, report Linda Chao (University of California, San Francisco, USA) and her colleagues.
“Future work will be needed to examine if effective treatment of disturbed sleep leads to improved frontal lobe structural and functional integrity”, the team writes in Sleep.
Chao’s group studied 144 Gulf War Veterans; 15% were female and the average age was 45 years. All underwent magnetic resonance imaging in order to quantify brain volumes.
The mean total score on the Pittsburgh Sleep Quality Index (PSQI) was 8.6. PSQI scores positively and significantly correlated with the current and lifetime severity of post-traumatic stress disorder (PTSD; as indicated by scores on the Clinician Administered PTSD scale) and with depressive symptoms (as indicated by the Hamilton Depression Scale scores).
PSQI scores also positively correlated with the presence of Gulf War Illness, adult trauma and use of psychotropic medication.
Interestingly, sleep quality was significantly inversely associated with total and regional volumes of cortical grey matter. Specifically, higher PSQI scores correlated with lower middle frontal, frontal pole, orbitofrontal and anterior cingulate cortex volumes.
These associations remained statistically significant after adjusting for age, body mass index, presence of snoring, sarin exposure and past alcohol and substance use. They were also significant in the subset of 108 patients without current psychiatric comorbidities.
There was no association between PSQI and hippocampal volume, however.
The researchers say their findings “support the frontal lobe hypothesis, which posits that sleep deprivation acts primarily on the frontal lobe to produce frontal cortex dysfunction.”
While admitting that the mechanisms underlying their observations remain unclear, the team conclude: “[O]ur results suggest that poor sleep quality, which has been linked to impaired psychosocial, physical, and occupational functioning, is associated with frontal lobe atrophy independent of trauma exposure, current and lifetime PTSD symptom severity, current [major depressive disorder], and Gulf War Illness status.”
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