Sex-specific hippocampus volume changes in obstructive sleep apnea

Neuroimage Clin. 2018 Jul 27;20:305-317. doi: 10.1016/j.nicl.2018.07.027. eCollection 2018.

Abstract

Introduction: Obstructive sleep apnea (OSA) patients show hippocampal-related autonomic and neurological symptoms, including impaired memory and depression, which differ by sex, and are mediated in distinct hippocampal subfields. Determining sites and extent of hippocampal sub-regional injury in OSA could reveal localized structural damage linked with OSA symptoms.

Methods: High-resolution T1-weighted images were collected from 66 newly-diagnosed, untreated OSA (mean age ± SD: 46.3 ± 8.8 years; mean AHI ± SD: 34.1 ± 21.5 events/h;50 male) and 59 healthy age-matched control (46.8 ± 9.0 years;38 male) participants. We added age-matched controls with T1-weighted scans from two datasets (IXI, OASIS-MRI), for 979 controls total (426 male/46.5 ± 9.9 years). We segmented the hippocampus and analyzed surface structure with "FSL FIRST" software, scaling volumes for brain size, and evaluated group differences with ANCOVA (covariates: total-intracranial-volume, sex; P < .05, corrected).

Results: In OSA relative to controls, the hippocampus showed small areas larger volume bilaterally in CA1 (surface displacement ≤0.56 mm), subiculum, and uncus, and smaller volume in right posterior CA3/dentate (≥ - 0.23 mm). OSA vs. control males showed higher bilateral volume (≤0.61 mm) throughout CA1 and subiculum, extending to head and tail, with greater right-sided increases; lower bilateral volumes (≥ - 0.45 mm) appeared in mid- and posterior-CA3/dentate. OSA vs control females showed only right-sided effects, with increased CA1 and subiculum/uncus volumes (≤0.67 mm), and decreased posterior CA3/dentate volumes (≥ - 0.52 mm). Unlike males, OSA females showed volume decreases in the right hippocampus head and tail.

Conclusions: The hippocampus shows lateralized and sex-specific, OSA-related regional volume differences, which may contribute to sex-related expression of symptoms in the sleep disorder. Volume increases suggest inflammation and glial activation, whereas volume decreases suggest long-lasting neuronal injury; both processes may contribute to dysfunction in OSA.

Keywords: AHI, apnea-hypopnea index; Autonomic; CA, cornu ammonis; Inflammation; Intermittent hypoxia; Neuroimaging; OSA, obstructive sleep apnea; Oxidative stress.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Female
  • Hippocampus / diagnostic imaging*
  • Hippocampus / physiopathology
  • Humans
  • Magnetic Resonance Imaging / methods*
  • Male
  • Middle Aged
  • Organ Size
  • Polysomnography / methods
  • Sex Characteristics*
  • Sleep Apnea, Obstructive / diagnostic imaging*
  • Sleep Apnea, Obstructive / physiopathology