Fine particulate matter and sleep-disordered breathing severity in a large Italian cohort.

BACKGROUND: Air pollution and obstructive sleep apnea (OSA) are both linked with cardiovascular co-morbidities and share similar pathophysiological mechanisms. A causal association between the two has been postulated. However, the results of the studies on this topic are conflicting mainly because of the lack of adjustment for important confounders such as seasonality and temperature. We aimed to evaluate if such an association exists in a highly polluted area like Lombardy region (Italy) when accounting for all confounders. METHODS: Data of adult patients seen at the Sleep Disorder Centre in Milan from 2010 to 2020 were analysed and the main polygraphic data were retrieved. Air pollutant concentrations of the following pollutants NO2, O3, PM2.5, and PM10 were collected through monitoring stations. RESULTS: A total of 3493 patients were included: males (2358, 67.5%) mean age 60.1 (SD = 14.3) years, BMI 29.2 (6.2) kg/m2, mean AHI 16.5 (18.1) events/h. After adjusting for all confounders, in the multivariable analysis, the only associations that remained significant were long-term exposure to O3 with indexes of OSA severity (AHI and ODI) but only in spring. Furthermore, a positive association was seen between long-term exposure to PM10 and ODI but in springtime only. CONCLUSION: The findings of the current study does not support an association between fine particulate matter and OSA severity.

Obstructive sleep apnea syndrome and autonomic dysfunction.

Autonomic nervous system (ANS) has been extensively explored in obstructive sleep apnea (OSA). Autonomic alterations in these patients have been described by means of several methods, evaluating ANS function both directly with microneurography and indirectly through baroreflex sensitivity (BRS, by the sequence method or the cross-spectral approach), heart rate variability analysis (HRV, both in the time and frequency domain) during sleep and wake, or conventional laboratory tests, including cold pressor test, hand grip test or measurement of urinary cathecolamine excretion. Several studies in OSA patients have shown ANS alterations, in particular sympathetic overactivity, both acutely during apnea events and chronically during the daytime, being both also involved in cardiovascular consequences of sleep disordered breathing. The association between OSA and sympathetic dysregulation suggests a dose response relationship between OSA severity and the degree of sympathetic overactivity and this association seems to be reversible as the treatment of OSA is implemented. Additionally ANS is involved in regulating visceral and humoral functions to maintain the body homeostasis and in reaction and adaptation to external and internal stressor stimuli. However, the vast majority of studies have focussed on cardiovascular alterations, which are easier to measure, somewhat neglecting the other functions regulated by ANS. More evidence is therefore needed to better characterize the impact that sleep disorder breathing may have on ANS both in the short and long term.

Elevated obstructive sleep apnoea risk score is associated with poor healing of diabetic foot ulcers: a prospective cohort study.

AIMS: To assess the prevalence of risk factors for obstructive sleep apnoea in people with diabetic foot ulcers and to determine whether this risk predicts diabetic foot ulcer healing. METHODS: We studied 94 consecutive people (69% men) with diabetic foot ulcers (Type 2 diabetes, n=66, Type 1 diabetes, n=28) attending a university hospital foot unit. All participants were screened for obstructive sleep apnoea using the STOP-BANG questionnaire, with a score ≥4 identifying high risk of obstructive sleep apnoea. The primary outcome was poor diabetic foot ulcer healing, defined as diabetic foot ulcer recurrence (diabetic foot ulcers which healed and re-ulcerated in same anatomical position) and/or diabetic foot ulcer persistence (no evidence of healing on clinical examination). All participants were evaluated at 12 months. RESULTS: Of the 94 participants, 60 (64%) had a STOP-BANG score ≥4. Over 12 months, 27 participants with a score ≥4 had poor diabetic foot ulcer healing as compared to seven with a score <4 (45% vs 20.5%; P=0.025). A STOP-BANG score ≥4 significantly increased the relative risk of poor healing more than twofold, independently of other risk factors in multivariable analyses. CONCLUSIONS: There is a high prevalence of features and risk of obstructive sleep apnoea in people with diabetic foot ulcers. A STOP-BANG score ≥4 predicts poor diabetic foot ulcer healing. Obstructive sleep apnoea may be a potential, modifiable risk factor/treatment target to improve diabetic foot ulcer outcomes.

Characterisation of sleep disturbances in postural orthostatic tachycardia syndrome: a polysomnography-based study.

BACKGROUND AND AIM: Postural orthostatic tachycardia syndrome (PoTS) has been frequently associated with sleep disturbances but objective sleep data are lacking. In addition, although regional autonomic denervation has been described, less is known about autonomic nervous activity overnight in these patients. PATIENTS/METHODS: A full polysomnography and heart rate variability were performed on 37 patients diagnosed with PoTS . In addition, a multiple sleep latency test (MSLT) was conducted on a subgroup of patients with excessive daytime sleepiness. RESULTS: The polysomnographic data did not show major pathological findings except the percentage spent in rapid eye movement (REM) sleep which was slightly reduced at 18.4%. The MSLT did not confirm excessive daytime sleepiness as median mean sleep latency was 14.4 min (11.8-17.5). When comparing patients with and without subjective daytime sleepiness, it was found that the latter had a reduced parasympathetic activation at night as expressed by the average high frequency [6936.5 ms(2) (6028.2-8675.5) vs. 4689.5 (3922.7-7685.2) p < 0.05]. CONCLUSION: Patients with PoTS do not exhibit polysomnographic findings consistent with relevant sleep pathologies nor objective daytime sleepiness. Subjective daytime sleepiness is associated with enhanced activation of the parasympathetic nervous system.