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.

[Chronic cough in the elderly is associated with expiratory flow limitation]. / La toux chronique du sujet âgé est associée à une limitation expiratoire des débits.

As chronic respiratory symptoms and the presence of expiratory flow limitation (EFL) are commonly reported in the elderly, we investigated whether they were associated in a population of 75 years old volunteers. We analyzed the results of a prevalence survey of chronic respiratory symptoms and respiratory infections, and performed spirometry and measured EFL after application of a negative expiratory pressure at the mouth (NEP). EFL was present in 170 (46%) subjects, a chronic cough in 49 (13%), chronic sputum in 58 (29%) and a history of respiratory infection in 62 (17%). Chronic cough and the composite outcome "chronic cough or sputum" were significantly associated with the presence of EFL (respectively 60% vs. 43%, OR=2.04 [1.09 to 3.78], P=0.023, and 56% vs. 43%, OR=1.74 [1.05 to 2.87], P=0.04), after controlling for smoking or airway obstruction. History of respiratory infections were not associated with an increased prevalence of EFL. We concluded that the presence of a LED could be an interesting indicator of respiratory aging. Its detection could be advocated in elderly subjects presenting with respiratory symptoms.

Is tidal expiratory flow limitation predictive of sleep-related disorders in the elderly?

Sleep-related disorders represent an important health burden and their prevalence increases with age. In patients with snoring or sleepiness, the presence of expiratory flow limitation (EFL), determined via the negative expiratory pressure (NEP) method, is related to the apnoea/hypopnoea index (AHI). In this study, we examined whether EFL can be used to predict obstructive sleep apnoea syndrome (OSAS) in healthy asymptomatic older subjects. A group of 72-yr-old subjects (n = 448, 44% males) with a mean body mass index of 25.5±3.8 kg·m(-2) were examined. All subjects underwent spirometry, NEP (-5 cmH(2)O, sitting position) and ventilatory polygraphy (VP). Spirometry was within normal values in 88% of the group and EFL was present in 143 (32%) subjects with a higher prevalence in females (89 out of 249 versus 54 out of 199 in females and males, respectively). VP showed an AHI<15 h(-1) in 238 subjects (53%) and OSAS with an AHI ≥15 h(-1) in 47%. EFL was found in 15% of subjects with OSAS. Consequently, EFL had low sensitivity and specificity in the prediction of OSAS (31.4% and 67.7%, respectively). We conclude that the prevalence of EFL is elevated in healthy older subjects and cannot be used to predict the presence of sleep-related disorders in an older population.

Association between C-reactive protein and unrecognised sleep-disordered breathing in the elderly.

Elevated levels of C-reactive protein (CRP) have been reported in patients with sleep-disordered breathing (SDB) and may represent an inflammatory marker of cardiovascular risk. However, the association of CRP with SBD in presumed healthy elderly subjects is unknown. In total, 851 (58.5% females) 68-yr-old subjects, who were free of any known cardiac or sleep disorders, were prospectively examined. Subjects underwent unattended polygraphy, and the apnoea/hypopnoea index (AHI) and oxyhaemoglobin desaturation index (ODI) were assessed. Elevated levels of CRP were found on the morning after the sleep study in patients with more severe SDB. A significant correlation was found between CRP levels, time spent at night with arterial oxygen saturation <90% and ODI. No association was found between CRP levels and AHI. After adjustments for body mass index, smoking status, hypertension, diabetes and dyslipidaemia, a significant association remained between CRP levels and ODI >10 events.h(-1). CRP levels were frequently increased in a large sample of elderly subjects free of major cardiovascular disease. CRP levels were not correlated with the AHI and the indices of sleep fragmentation; the ODI >10 events.h(-1) was the strongest predictor of raised CRP level. The present results suggest that, in the elderly, intermittent hypoxaemia may underlie inflammatory processes leading to cardiovascular morbidity.