Gender difference in relationship of apnoea/hypopnoea index with body mass index and age in the Omani population

Obstructive sleep apnoea/hypopnoea syndrome [OSAHS] is a disorder characterised by repetitive upper airway collapse during sleep in association with daytime sleepiness. It has an estimated prevalence of 2% and 4% among middle-aged women and men respectively. The aim of the study was to look at the association of body mass index [BMI], age and gender and prevalence of OSAHS in the Omani population. Polysomnography reports and hospital medical records of all patients who took part in the Sleep Study at the Sleep Laboratory of the Clinical Physiology Department, Sultan Qaboos University Hospital, between January 1995 and December 2006, were retrospectively reviewed. Data from both sources was gathered and analysed. A total of 1,042 sleep studies were conducted with 608 valid studies for analysis. The study showed that the apnoea/ hypopnoea index [AHI] >15 was more prevalent in men compared to women [47.9% versus 33.5%, P = 0.001]. There was significant correlation of AHI with BMI [P <0.0001] among men compared to women [P = 0.1]; however, age was significantly correlated with AHI among women [P <0.0001], but not with men [P = 0.1]. The results indicate that there is a gender difference in the prevalence of OSAHS and obesity is a major risk factor for OSAHS among Omani men whereas age is found to be a risk factor for OSAHS among women

Screening of patients with snoring and obstructive sleep opnoea using heart rate variability indices

Snoring and obstructive sleep apnea [OSA] are common disorders. Snoring associated with excessive daytime sleepiness is the most prevalent symptoms of OSA. Heart rate variability [HRV] is altered in patients with OSA and the degree of alteration may be linked to the severity of OSA. Alterations in HRV in 24 hour tachograms have recently been used in screening OSA patients. Autonomic components causing HRV can be reliably studied using spectral analysis techniques involving fast Fourier transformation [FFT]. Twenty-three subjects, 13 with severe OSA and 10 controls matched for age and body mass index, were selected from patients who had undergone polysomnography [PSG] for snoring at Sultan Qaboos University Hospital, Oman. A 24- hour electrocardiogram [ECG] Holter recording was done at home, starting at 10am. Spectral analysis of ECG from sleep Holter and PSG recordings was analysed using fast Fourier transformation [FFT]. The ECG RR intervals of snorers with OSA were significantly shorter than in snorers without OSA [p <0.01]. The low frequency [LF] spectral densities of HRV from polysomnography and Holter were significantly higher in OSA patients than in snorers, [p < 0.0001]. The power spectral density of the high frequency bands was similar in the two groups. The overnight ECG Holter accurately identified all 13 snorers with severe OSA. The spectral power of the LF band obtained using FFT of sleep HRV from Holter tachograms may be a useful and cost effective test in identifying snorers with severe OSA

Non-dipping blood pressure in normotensive patients with obstructive sleep apnea

To investigate circadian blood pressure profiles in normotensive patients with moderate to severe obstructive sleep apnea [OSA], in relation to their apnea indices and left ventricular parameters, we studied twenty one male patients with clinic blood pressures of< 140/90 mmHg. They were matched for age and body mass index [BMI] and all were heavy snorers. They underwent overnight polysomnography, 24 h non-invasive arterial blood pressure monitoring [ABPM] and echocardiography. Patients with a nocturnal reduction in average daytime systolic and diastolic blood pressure of less than 10% were considered non-dippers. Nine patients were non-dippers and 12 were dippers. In the non-dipper group asleep systolic and diastolic blood pressure were significantly higher than in the dipper group, [P< 0.0001 and P<0.01 respectively]. There were no significant differences between the apnea/hypopnea [AHI] and the oxygen desaturation [ODI] indices of the dipper and the non-dipper groups. However, left ventricular parameters were significantly higher in the non-dipper than in the dipper group: left ventricular mass index [LVMI, P<0.001], posterior wall thickness [PWT, P<0.001], interventricular septal thickness [IVST, P<0.001] and relative wall thickness [RWT, P<0.01]. In this preliminary study an absent or reduced blood pressure fall during sleep in normotensive patients with moderate to severe OSA cannot be explained by the severity of the apnea alone. Left ventricular hypertrophy, though may be a sequel to the non-dipper situation may also be the cause of it