Chronotype, Longitudinal Volumetric Brain Variations Throughout Adolescence, and Depressive Symptom Development.

OBJECTIVE: Adolescence is a critical period for circadian rhythm, with a strong shift toward eveningness around age 14. Also, eveningness in adolescence has been found to predict later onset of depressive symptoms. However, no previous study has investigated structural variations associated with chronotype in early adolescence and how this adds to the development of depressive symptoms. METHOD: Assessment of 128 community-based adolescents (51% girls) at age 14 and 19 years was performed. Using whole-brain voxel-based morphometry, baseline (at age 14) regional gray matter volumes (GMVs), follow-up (at age 19) regional GMVs, and longitudinal changes (between 14 and 19) associated with Morningness/Eveningness Scale in Children score and sleep habits at baseline were measured. The association of GMV with depressive symptoms at 19 years was studied, and the role of potential clinical and genetic factors as mediators and moderators was assessed. RESULTS: Higher eveningness was associated with larger GMV in the right medial prefrontal cortex at ages 14 and 19 in the whole sample. GMV in this region related to depressive symptoms at age 19 in catechol-O-methyltransferase (COMT) Val/Val, but not in Met COMT, carriers. Larger GMV also was observed in the right fusiform gyrus at age 14, which was explained by later wake-up time during weekends. CONCLUSION: In adolescence, eveningness and its related sleep habits correlated with distinct developmental patterns. Eveningness was specifically associated with GMV changes in the medial prefrontal cortex; this could serve as a brain vulnerability factor for later self-reported depressive symptoms in COMT Val/Val carriers.

Topography of homeostatic sleep pressure dissipation across the night in young and middle-aged men and women.

Decline in slow-wave activity (SWA) across the night is believed to reflect dissipation of the homeostatic sleep drive. This study evaluated the effects of age, sex and topography on SWA dissipation. The sleep electroencephalogram of 48 young [22 women, 26 men; mean = 23.3 years; standard deviation (SD) = 2.4] and 39 middle-aged (21 women, 18 men; mean = 51.9 years; SD = 4.6) healthy volunteers was analysed. Spectral analysis (0.5-22.0 Hz) was performed per non-rapid eye movement period for Fp1, F3, C3, P3 and O1. SWA (1.0-5.0 Hz) dissipation was modelled using linear and exponential decay functions applied to each age and sex subgroup data set for each derivation. The relative adequacy of both functions was compared using Akaike's information criterion. Results suggest that the exponential model provides a better data fit than the linear fit independently of age, gender and brain location. In women, age reduced the span (distance between the y intercept and the asymptote) of SWA decay in Fp1, F3, P3 and O1. In men, however, the effect of age on the span of SWA decay was limited to Fp1 and F3. In all age and sex subgroups, anterior regions showed a higher span than posterior regions. The asymptote was lower in anterior regions in young but not in middle-aged subjects. These results suggest that the homeostatic process operates on a larger scale in anterior regions. Importantly, ageing reduced the scale of homeostatic dissipation in both sexes, but this effect was more widespread across the brain in women.

Mild cognitive impairment in rapid eye movement sleep behavior disorder and Parkinson's disease.

OBJECTIVE: To investigate the frequency and subtypes of mild cognitive impairment (MCI) in idiopathic rapid eye movement sleep behavior disorder (RBD) and Parkinson's disease (PD) in association with RBD. METHODS: One hundred and twelve subjects without dementia or major depression including 32 idiopathic RBD patients, 22 PD patients with polysomnography-confirmed RBD, 18 PD patients without RBD, and 40 healthy control subjects, underwent a comprehensive neuropsychological evaluation. We compared the proportion of patients with MCI between groups using standard diagnostic criteria. RESULTS: MCI was found in 50% of idiopathic RBD patients and 73% of PD patients with RBD. In contrast, only 11% of PD patients without RBD and 8% of control subjects had MCI. The presence of MCI was significantly greater in idiopathic RBD patients and PD patients with RBD than in PD patients without RBD and control subjects. PD patients with RBD also performed worse than idiopathic RBD patients on neuropsychological tests assessing visuoconstructional and visuoperceptual abilities. INTERPRETATION: In both its association with PD and its idiopathic form, RBD is an important risk factor for MCI. Except for visuoconstructional and visuoperceptual problems, RBD may be an important determinant of cognitive impairment in PD. Ann Neurol 2009;66:39-47.

Does age worsen EEG slowing and attention deficits in obstructive sleep apnea syndrome?

OBJECTIVE: The aim of this study was to determine whether EEG slowing is more pronounced in older than younger OSAS patients and to verify whether this cortical slowing is correlated to daytime performance, respiratory perturbation and sleep fragmentation. METHODS: Twelve young OSAS patients (mean age 38.2+/-2.0 y) and 13 older OSAS patients (mean age 62.2+/-1.9 y) along with 13 young controls (mean age 35.8+/-2.0 y) and 14 older controls (mean age 60.2+/-2.0 y) underwent a polysomnographic evaluation followed by a waking EEG recording. As a global index of cortical slowing, a ratio of slow-to-fast frequencies was calculated in all cortical regions. Daytime performance was assessed using the four choice reaction time test. RESULTS: Differences in waking EEG and in daytime performance were analyzed by ANOVAs with Group and Age as factors. Waking EEG did not yield a Group by Age interaction. OSAS patients had higher ratios across all regions than controls. Similarly, daytime performance revealed no Group by Age interaction. However, OSAS patients showed more lapses than controls and older subjects were slower than younger subjects. CONCLUSIONS: Our results indicate that age does not interact with OSAS to worsen the severity of cortical slowing, but age can add to the OSAS effect to worsen daytime performance deficits in OSAS patients. SIGNIFICANCE: The daytime performance deficits observed particularly in elderly OSAS patients warrant a careful clinical assessment of these patients to prevent accidents and injuries.

Potential early markers of Parkinson disease in idiopathic REM sleep behavior disorder.

BACKGROUND: Idiopathic REM sleep behavior disorder (RBD) is characterized by loss of atonia during REM sleep, resulting in motor activity during dreams. Studies estimate that approximately half of patients with RBD will eventually develop Parkinson disease (PD), so RBD may be an indicator of presymptomatic PD. Several potential early diagnostic markers of PD have been proposed, but they have generally not been tested in presymptomatic PD. The authors hypothesized that these markers may be abnormal in idiopathic RBD. METHODS: The authors compared 25 patients with polysomnography-confirmed RBD without PD with age- and sex-matched controls. Color vision, olfaction, quantitative motor testing, and indices of depression, personality, and autonomic function were examined. RESULTS: Patients demonstrated significant impairment in color discrimination and olfactory function. Patients had subtle abnormalities on quantitative testing of motor and gait speed. Autonomic symptoms were more common in patients than controls. Abnormalities were heterogeneous, with some patients scoring normally on all domains, whereas others were severely impaired on multiple domains. Dysfunction on tests of olfactory function, color vision, and motor speed were highly correlated, such that patients who performed poorly on one test tended to perform poorly on the others. CONCLUSIONS: Many potential early markers of Parkinson disease are significantly abnormal in idiopathic REM sleep behavior disorder. These abnormalities are present in approximately half of the patients, suggesting a heterogenous pathophysiology.

Slow-wave sleep and delta power in rapid eye movement sleep behavior disorder.

Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by the loss of normal muscle atonia during REM sleep, leading to an increase of phasic muscle activity and complex motor behaviors during the night. There is some evidence that RBD patients have more of slow-wave sleep (SWS) than healthy elderly subjects. No study has looked at quantitative electroencephalogram analysis during non-REM sleep in either primary or secondary RBD. The aim of this study was to assess the increase of SWS and to analyze different electroencephalographic frequency ranges during non-REM sleep in 28 idiopathic RBD patients compared with 28 age- and sex-matched healthy volunteers. Idiopathic RBD patients spent more time in SWS (men: 1.4%; women: 5.9%) than control subjects (men: 0.4%; women: 0.6%; p = 0.004). Spectral analyses demonstrated that idiopathic RBD patients had increased all-night delta power in comparison with control subjects (p = 002). This study shows an increase of SWS and power in the delta band during non-REM sleep in idiopathic RBD patients compared with control subjects. Results are discussed about the possible nigrostriatal dopaminergic impairment in RBD patients and the association between RBD and neurodegenerative disorders.