Subjective and polysomnographic evaluation of sleep in mitochondrial optic neuropathies

Nocturnal vestibular stimulation using a rocking bed improves a severe sleep disorder in a patient with mitochondrial disease

Mitochondrial diseases are rare genetic disorders often accompanied by severe sleep disorders. We present the case of a 12-year-old boy diagnosed with a severe primary mitochondrial disease, exhibiting ataxia, spasticity, progressive external ophthalmoplegia, cardiomyopathy and severely disrupted sleep, but no cognitive impairment. Interestingly, his parents reported improved sleep during night train rides. Based on this observation, we installed a rocking bed in the patient's bedroom and performed different interventions, including immersive multimodal vestibular, kinesthetic and auditory stimuli, reminiscent of the sensory experiences encountered during train rides. Over a 5-month period, we conducted four 2-week nocturnal interventions, separated by 1-week washout phases, to determine the subjectively best-perceived stimulation parameters, followed by a final 4-week intervention using the optimal parameters. We assessed sleep duration and quality using the Mini Sleep Questionnaire, monitored pulse rate changes and used videography to document nocturnal interactions between the patient and caregivers. Patient-reported outcome measures, clinical examinations and personal outcomes of specific interests were used to document daytime sleepiness, restlessness, anxiety, fatigue, cognitive performance and physical posture. In the final 4-week intervention, sleep duration increased by 25%, required caregiver interactions reduced by 75%, and caregiving time decreased by 40%. Subjective fatigue, assessed by the Checklist Individual Strength, decreased by 40%, falling below the threshold of severe fatigue. Our study suggests that rocking beds could provide a promising treatment regime for selected patients with persistent severe sleep disorders. Further research is required to validate these findings in larger patient populations with sleep disorders and other conditions.

Sleep Quality in Patients With Ocular Graft-Versus-Host Disease After Allogeneic Hematopoietic Stem Cell Transplantation

OBJECTIVES

To investigate the sleep quality in patients with ocular graft-versus-host disease (oGVHD) compared with patients without oGVHD after allogeneic hematopoietic stem cell transplantation (alloHCT) and healthy controls.

METHODS

This cross-sectional study analyzed 142 patients after alloHCT including 94 patients with oGVHD and 48 without. Fifty healthy controls were also enrolled. oGVHD was diagnosed according to International Chronic Ocular GVHD Consensus Group (ICOGCG) criteria. Sleep quality was assessed by the Chinese version of the Pittsburgh Sleep Quality Index (CPSQI). Poor sleep quality was defined as CPQSI score greater than 6.

RESULTS

Patients after alloHCT demonstrated a significantly higher CPQSI score than those of controls {7.0 [interquartile range (IQR) 5.0-10.0] vs. 5.5 [IQR 4.8-7.0], P =0.002}, especially in the oGVHD subgroup (7.5 [IQR 5.0-11.0] vs. 6.0 [IQR 5.0-8.0], P =0.04) with nearly double prevalence of poor sleep quality (58 [62%] vs. 18 [37%], P =0.006). Poor sleep quality was strikingly correlated with oGVHD diagnosis (adjusted odds ratio [OR]=2.55, 95% confidence interval [CI]: 1.02-6.34, P =0.04) and systemic immunosuppressants (adjusted OR=2.61, 95% CI: 1.32-5.71, P =0.02). Among the ocular parameters, poor sleep quality was significantly associated with higher ICOGCG score (adjusted OR=1.20, 95% CI: 1.03-1.39, P =0.02) and lower tear film break-up time (adjusted OR=0.85, 95% CI: 0.74-0.99, P =0.05).

CONCLUSIONS

Poor sleep quality was associated with an increased severity of oGVHD and tear film instability in the long-term alloHCT survivorship.

Mitochondria's role in sleep: Novel insights from sleep deprivation and restriction studies

OBJECTIVES/METHODS

The biology underlying sleep is not yet fully elucidated, but it is known to be complex and largely influenced by circadian rhythms. Compelling evidence supports of a link among circadian rhythms, sleep and metabolism, which suggests a role for mitochondria. These organelles play a significant role in energy metabolism via oxidative phosphorylation (OXPHOS) and several mitochondrial enzymes display circadian oscillations. However, the interplay between mitochondria and sleep is not as well-known. This review summarises human and animal studies that have examined the role of mitochondria in sleep. Literature searches were conducted using PubMed and Google Scholar.

RESULTS

Using various models of sleep deprivation, animal studies support the involvement of mitochondria in sleep via differential gene and protein expression patterns, OXPHOS enzyme activity, and morphology changes. Human studies are more limited but also show differences in OXPHOS enzyme activity and protein levels among individuals who have undergone sleep deprivation or suffer from different forms of insomnia.

CONCLUSIONS

Taken altogether, both types of study provide evidence for mitochondria's involvement in the sleep-wake cycle. We briefly discuss the potential clinical implications of these studies.

Sleep Disorders in Mitochondrial Diseases

PURPOSE OF REVIEW

We aim to summarize the sleep disorders reported in patients affected by primary mitochondrial dysfunctions and describe the association with their clinical and molecular characteristics.

RECENT FINDINGS

Sleep complaints are prevalent in mitochondrial disorders. Sleep-disordered breathing is the main sleep disorder reported in mitochondrial diseases. OSA and CSA are, respectively, more frequently associated with patients characterized by the prevalent involvement of the skeletal muscle and the predominant involvement of the central nervous system. Other sleep disorders, such as restless legs syndrome, have been rarely described. Sleep disorders are frequently associated with primary mitochondrial disorders, and the clinical phenotypes affect the type of sleep disturbance associated with the mitochondrial dysfunction. A polysomnographic study should be performed in every subject with this neurogenetic disorder both at diagnosis and during follow-up for the numerous adverse clinical outcomes associated with sleep disorders and the frailty of mitochondrial patients.