CHANGES IN BRAIN MORPHOLOGY ASSOCIATED WITH OBSTRUCTIVE SLEEP APNEA

Mary J. Morrell et al. 2003

Presented by Karen Hu

PSYCH 260

WHAT IS OBSTRUCTIVE SLEEP APNEA ?

INTRODUCTION.

Obstructive Sleep Apnea (OSA) : • Caused by upper airway dysfunction

during sleep - repeated arousals/ awakening - periodic breathing

• Breathing stops for ≥ 10 seconds

- episodic hypoxemia • Periods of significant decrease in O2

saturation in the blood

INTRODUCTION.

Obstructive Sleep Apnea (OSA) affects:

• 1-4% of middle aged adults

• 24- 30% of elderly

SYMPTOMS • Excessive daytime sleepiness

and fatigue• Loud snoring • Increased risk of hypertension

and cardiovascular diseases• Cognitive deficits

NO!

INTRODUCTION.

Cognitive Deficits by OSA:

OSA patients have shown impairment in memory, learning and attention

HIPPOCAMPUS: region closely associated with neural processing of memory

- sensitive to hypoxic (low O2) conditions

CURRENT STUDY

• Investigates the effects of OSA on the morphology or structural changes of the brain • Focusing on the CA1

region of HIPPOCAMPUS and other cortical regions

HYPOTHESIS: There would be a focal loss of grey matter within the hippocampus and other cortical areas linked with memory function

METHODS

• MRI scan • Newly OSA diagnosed

patients selected from sleep clinic

• 7 OSA patients and 7 non-apneic controls – Age range= 28-65

yrs old • All male and right

handed

METHODS

• Voxel based morphometry (VBM) • Images were normalized and compared

to a standardized brain template • Signal intensity represented grey

matter concentration• Images were compared to determine

any significance

RESULTS

Control vs. OSA

Significantly lower grey matter concentration in the OSA patients in the LEFT HIPPOCAMPUSby 6%

RESULTS

• NO SIGNIFICANT DIFFERENCE in focal grey matter concentration in the RIGHT HIPPOCAMPUS and other cortical regions

DISCUSSION

• Reduction of grey matter in left hippocampus:– Hippocampal sensitivity to low O2 conditions

cause neurons to die off• Absence of grey matter difference in the right

hippocampus – Due to relatively moderate hypoxemia in the

OSA patients • Repetitive hypoxia reduces neuron excitability in

the CA1 region – Similar effects of sleep deprivation

• Findings emphasize that grey matter loss is associated with less severe OSA

LIMITATIONS

• Small sample size – Limited validity of results and implications

• Obese patients were excluded • Only male subjects used • Could not relate grey matter loss directly to

cognitive deficits or specific characteristics of OSA

FUTURE IMPLICATIONS

- relate severity of OSA to grey matter loss - larger sample size, include females - explore how sleep fragmentation affects brain structure- correlate grey matter loss with cognitive deficits

PERSONAL THOUGHTS

- Short and simplified - Well organized - Easy to understand - Addressed just the

changes in morphology

- At times, lacked detail - Discussion and intro

was weak - Lacked a strong

possible implication

- Did not specify which cortical areas they were comparing

FINAL EXAM SWAG.

Obstructive Sleep Apnea ( OSA) : - repeated arousal, periodic breathing, episodic hypoxemia, fragmented sleep- leads to damage in cortical areas associated with memory and learning, cognitive deficits and excessive daytime sleepiness

Methods- Voxel based, MRI, 7 OSA patients, 7 controls, all right-handed males

Results - significantly lower grey matter in left hippocampus in OSA group - no significant grey matter differences in right hippocampus or other cortical areas - no significant difference in total volume of grey matter

Discussion - low O2 levels may have resulted in grey matter loss in left hippocampus - no significance in right hippocampus due to moderate OSA severity - repetitive hypoxia reduces neuron excitability in CA1 of hippocampus

REFERENCE

Morrell, M.J., McRobbie, D.W., Quest, R.A., Cummin, A.R.C., Ghiassi, R. and Corfield, D. 2003. Changes in brain morphology associated with obstructive sleep apnea. Sleep Medicine, 4, 451-454.

QUESTIONS?