Florian Chouchou

Sex differences in obstructive sleep apnoea in an elderly French population

Obstructive sleep apnoea (OSA) affects females and males differently, and increases in prevalence with age. The aim of the present study was to characterise clinical, anthropometric and polygraphic sex differences in a large elderly OSA population. A total of 641 subjects aged 68 yrs were examined. Measurements of fat mass, using dual-energy X-ray absorptiometry (DEXA) and polygraphy, were obtained in all subjects. An apnoea/hypopnoea index (AHI) of >15 events·h−1 identified the presence of OSA. OSA was diagnosed in 57% of the sample, 34% having a mild form and 23% having an AHI of >30 events·h−1. Females with OSA exhibited a lower AHI, less severe hypoxaemia and greater peripheral fat mass, and frequently reported anxiety and depression. Comparison of females with and without OSA did not reveal significant differences in clinical, anthropometric and DEXA data. After adjustment for body mass index, hypertension, diabetes, smoking, anxiety and depression, logistic regression analysis revealed that the presence of hypertension was significantly associated with OSA risk in females (OR 1.52, p = 0.04). In a general community healthy population, the prevalence of undiagnosed OSA in females increases with age, with a risk similar to that in males. In females, the clinical spectrum, anthropometric data and fat distribution appear to be more sex-related than OSA-dependent. The occurrence of OSA contributes to hypertensive risk in elderly females.

Sympathetic overactivity due to sleep fragmentation is associated with elevated diurnal systolic blood pressure in healthy elderly subjects: the PROOF-SYNAPSE study

AIMS Sleep fragmentation is a landmark of sleep disorders, because microarousals are systematically associated with sympathetic surges (i.e., sympathetic arousals). However, the impact of sympathetic sleep fragmentation on blood pressure (BP) remains understudied. We assessed the relationships between 24 h ambulatory BP monitoring, the autonomic arousal index (AAI) derived from pulse transit time, and heart rate variability indices. We hypothesized that repeated sympathetic arousals during sleep are associated with elevated BP in a large population of elderly volunteers. METHODS AND RESULTS Volunteer subjects (n = 780, 57.4% women) with a mean age of 68.7 years and free of known sleep-disordered breathing, coronary heart diseases, and neurological disorders underwent polygraphy, 24 h ECG Holter monitoring, and 24 h ambulatory BP monitoring. Multivariate regressions showed that sleep fragmentation, expressed by AAI, was associated with elevated diurnal (P = 0.008) and 24 h (P = 0.005) systolic BP and higher risk for 24 h [odds ratio (OR): 1.70 (1.04-2.80), P = 0.036] systolic hypertension, independently of confounders such as sleep-disordered breathing, body mass index, sex, diabetes, hypercholesterolaemia, and self-reported sleep duration and quality. Increased AAI was associated with higher nocturnal and diurnal low-frequency power (P < 0.001) and low-to-high-frequency ratio (P < 0.001), suggesting nocturnal and diurnal sympathetic overactivity. CONCLUSION In healthy elderly subjects, repetitive sympathetic arousals during sleep are associated with elevated systolic BP and higher risk of hypertension, after controlling for confounders. Sympathetic overactivity is the proposed underlying mechanism. CLINICAL TRIAL REGISTRATION NCT00766584 and NCT00759304.

Is the Berlin questionnaire a useful tool to diagnose obstructive sleep apnea in the elderly

OBJECTIVE In the elderly, obstructive sleep apnea (OSA) is frequently under diagnosed. This study was undertaken to assess the accuracy of the Berlin questionnaire to diagnose OSA in a large healthy elderly population. PATIENTS AND METHODS Six hundred forty-three participants aged 65.6 years were examined. All subjects completed the Berlin questionnaire and underwent at-home respiratory recording. Presence of OSA was defined by an AHI>15. RESULTS Of the respondents, 202 subjects (31.4%) were in an OSA high-risk group according to the Berlin questionnaire. The high-risk subjects were significantly heavier, had greater waist and hip circumferences, higher AHI, and reported more frequently hypertension and diabetes. Habitual snoring was present in 54% of the sample, sleepiness in 12% of participants, and a BMI>30 and a history of hypertension in 42.1%. Being in the high-risk group predicted an AHI>15 with a sensitivity of 77%, a specificity of 39%, a positive predictive value of 63% and a negative predictive value of 55%. Among Berlin questionnaire categories, snoring correctly classified 61% of the sample and explained the 5% variance of AHI. CONCLUSIONS The Berlin questionnaire did not provide a high level of diagnostic specificity to discriminate OSA in an elderly population. Although not sufficiently accurate, this questionnaire can be used to identify subjects for sleep study assessment.

Heart rate variability: a tool to explore the sleeping brain?

Sleep is divided into two main sleep stages: (1) non-rapid eye movement sleep (non-REMS), characterized among others by reduced global brain activity; and (2) rapid eye movement sleep (REMS), characterized by global brain activity similar to that of wakefulness. Results of heart rate variability (HRV) analysis, which is widely used to explore autonomic modulation, have revealed higher parasympathetic tone during normal non-REMS and a shift toward sympathetic predominance during normal REMS. Moreover, HRV analysis combined with brain imaging has identified close connectivity between autonomic cardiac modulation and activity in brain areas such as the amygdala and insular cortex during REMS, but no connectivity between brain and cardiac activity during non-REMS. There is also some evidence for an association between HRV and dream intensity and emotionality. Following some technical considerations, this review addresses how brain activity during sleep contributes to changes in autonomic cardiac activity, organized into three parts: (1) the knowledge on autonomic cardiac control, (2) differences in brain and autonomic activity between non-REMS and REMS, and (3) the potential of HRV analysis to explore the sleeping brain, and the implications for psychiatric disorders.

Vestibular Responses to Direct Stimulation of the Human Insular Cortex

The present study provides a functional mapping of vestibular responses in the human insular cortex.

Cardiac sympathetic modulation in response to apneas/hypopneas through heart rate variability analysis.

Autonomic dysfunction is recognized to contribute to cardiovascular consequences in obstructive sleep apnea/hypopnea syndrome (OSAHS) patients who present predominant cardiovascular sympathetic activity that persists during wakefulness. Here, we examined 1) the factors that influence sympathetic cardiac modulation in response to apneas/hypopneas; and 2) the influence of autonomic activity during apneas/hypopneas on CA. Sixteen OSAHS patients underwent in-hospital polysomnography. RR interval (RR) and RR spectral analysis using wavelet transform were used to study parasympathetic (high frequency power: HFWV) and sympathetic (low frequency power: LFWV and LFWV/HFWV ratio) activity before and after apnea/hypopnea termination. Autonomic cardiac modulations were compared according to sleep stage, apnea/hypopnea type and duration, arterial oxygen saturation, and presence of CA. At apnea/hypopnea termination, RR decreased (p<0.001) while LFWV (p = 0.001) and LFWV/HFWV ratio (p = 0.001) increased. Only RR and LFWV/HFWV ratio changes were higher when apneas/hypopneas produced CA (p = 0.030 and p = 0.035, respectively) or deep hypoxia (p = 0.023 and p = 0.046, respectively). Multivariate statistical analysis showed that elevated LFWV (p = 0.006) and LFWV/HFWV ratio (p = 0.029) during apneas/hypopneas were independently related to higher CA occurrence. Both the arousal and hypoxia processes may contribute to sympathetic cardiovascular overactivity by recurrent cardiac sympathetic modulation in response to apneas/hypopneas. Sympathetic overactivity also may play an important role in the acute central response to apneas/hypopneas, and in the sleep fragmentation.

At 68 years, unrecognised sleep apnoea is associated with elevated ambulatory blood pressure

After the age of 65 yrs the specific impact of unrecognised sleep-related breathing disorders (SRBD) on 24-h blood pressure (BP) levels remains under debate. We tested the cross-sectional relationship between the severity of obstructive sleep apnoea/hypopnoea (OSAH) and the increase of BP using ambulatory BP monitoring (ABPM) in the PROOF (PROgnostic indicator OF cardiovascular and cerebrovascular events study)-SYNAPSE (Autonomic Nervous System Activity, Aging and Sleep Apnea/Hypopnea study) cohort. 470 subjects (aged 68 yrs) neither treated for hypertension nor diagnosed for SRBD were included. All subjects underwent ABPM, and unattended at-home polygraphic studies. OSAH was defined by an apnoea/hypopnoea index (AHI) >15·h−1. The severity of the sleep apnoea was also quantified as the index of dips in oxyhaemoglobin saturation >3% (ODI). Results are expressed in per protocol analysis. Severe OSAH (AHI >30·h−1, 17% of subjects) was associated with a significant 5 mmHg increase in both diurnal and nocturnal systolic BP (SBP), and with a nocturnal 3 mmHg increase in diastolic BP (DBP). Systolic (mean SBP >135 mmHg) or diastolic (mean DBP >80 mmHg) hypertension were more frequently encountered in subjects suffering from moderate (AHI 15–30) or severe OSAH. After adjustment, the independent association between severe OSAH and 24-h systolic hypertension remained significant (OR 2.42, 95% CI 1.1–5.4). The relationship was further reinforced when SRBD severity was expressed using ODI >10·h−1. The impact of unrecognised SRBD on BP levels also exists at the age of 68 yrs. The hypoxaemic load appears to be the pathophysiological cornerstone for such a relationship.

HRVanalysis: A Free Software for Analyzing Cardiac Autonomic Activity

Since the pioneering studies of the 1960s, heart rate variability (HRV) has become an increasingly used non-invasive tool for examining cardiac autonomic functions and dysfunctions in various populations and conditions. Many calculation methods have been developed to address these issues, each with their strengths and weaknesses. Although, its interpretation may remain difficult, this technique provides, from a non-invasive approach, reliable physiological information that was previously inaccessible, in many fields including death and health prediction, training and overtraining, cardiac and respiratory rehabilitation, sleep-disordered breathing, large cohort follow-ups, childrens autonomic status, anesthesia, or neurophysiological studies. In this context, we developed HRVanalysis, a software to analyse HRV, used and improved for over 20 years and, thus, designed to meet laboratory requirements. The main strength of HRVanalysis is its wide application scope. In addition to standard analysis over short and long periods of RR intervals, the software allows time-frequency analysis using wavelet transform as well as analysis of autonomic nervous system status on surrounding scored events and on preselected labeled areas. Moreover, the interface is designed for easy study of large cohorts, including batch mode signal processing to avoid running repetitive operations. Results are displayed as figures or saved in TXT files directly employable in statistical softwares. Recordings can arise from RR or EKG files of different types such as cardiofrequencemeters, holters EKG, polygraphs, and data acquisition systems. HRVanalysis can be downloaded freely from the Web page at: https://anslabtools.univ-st-etienne.fr HRVanalysis is meticulously maintained and developed for in-house laboratory use. In this article, after a brief description of the context, we present an overall view of HRV analysis and we describe the methodological approach of the different techniques provided by the software.

Sleep spindles and human cortical nociception: a surface and intracerebral electrophysiological study

Sleep spindle are usually considered to play a major role in inhibiting sensory inputs. Using nociceptive stimuli in humans, we tested the effect of spindles on behavioural, autonomic and cortical responses in two experiments using surface and intracerebral electroencephalographic recordings. We found that sleep spindles do not prevent arousal reactions to nociceptive stimuli and that autonomic reactivity to nociceptive inputs is not modulated by spindle activity. Moreover, neither the surface sensory, nor the insular evoked responses were modulated by the spindle, as detected at the surface or within the thalamus. The present study comprises the first investigation of the effect of spindles on nociceptive information processing and the results obtained challenge the classical inhibitory effect of spindles.

Heart rate increment in the diagnosis of obstructive sleep apnoea in an older population

OBJECTIVE To evaluate the ability of the heart rate power spectral density of the very low frequency component expressed as a percentage of the total power spectral band (%VLFI) to diagnose obstructive sleep apnoea (OSA) in the elderly. PATIENTS AND METHODS Eight hundred and thirty-two subjects aged 68.5±0.8 years were selected from the participants of a 7-year cross-sectional study on the association between OSA and vascular morbidity-mortality. All subjects underwent electrocardiogram Holter monitoring and an at-home polysomnogram to measure the apnoea/hypopnoea index (AHI). OSA was assessed as an AHI>15. RESULTS The very low, the low frequency powers, and the %VLFI increased in subjects with OSA and were correlated with the autonomic arousal index and AHI (p<0.0001). A %VLFI of 2.4% and 4% demonstrated a sensitivity of 62% and 69% and a specificity of 45% and 44% to predict OSA in the population. CONCLUSION The %VLFI did not provide a high level of diagnostic sensitivity and specificity at different degrees of OSA severity in an elderly healthy population. The ability for prediction was lower in mild cases and in women. These findings suggest that the ageing-related changes in the autonomic nervous system reduce the applicability of HRV to diagnose OSA in older populations.