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Gender Difference in Relationship of Apnoea/Hypopnoea Index with Body Mass Index and Age in the Omani Population
– Reported, January 13, 2012
Methods:
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.
Results:
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).
Conclusion:
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.
Obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is a disorder characterised by repetitive upper airway collapse during sleep associated with arterial oxygen desaturation. This leads to repetitive night awakenings and excessive daytime sleepiness.OSAHS has also been associated with adverse cardiovascular consequences such as hypertension,and ischaemic heart disease.Major aetiological factors, such as obesity, and craniofacial anatomic predisposition, are both genetically and environmentally influenced, and it is therefore pertinent to determine the prevalence of sleep apnoea in different populations.It was shown previously by Young et al. that the prevalence of OSAHS was 2% in women and 4% in men in subjects who had an apnoea/hypopnoea index (AHI) of more than 5 and had symptoms. AHI is determined by number of apnoeas and hypopnoeas per hour of sleep. Duran et al. showed that the prevalence was higher with AHI of more than 5 and no symptoms, but with marginal gender difference between males and females. However, the gender difference became more obvious with higher levels of AHI with higher prevalence among men in all age groups.Nevertheless, gender differences in OSAHS prevalence could not be well established due to controversial results.
Obesity is the main risk factor for OSAHS and more than 80% of OSAHS patients have a body mass index (BMI) of more than 30 Kg/m.2,8 Recently, obesity has been found to be a major health problem in the Omani population with increasing prevalence in relatively young subjects.9 Nevertheless, age also has a major role in increasing the prevalence of OSAHS.To date, there has been scanty documentation of the gender difference in the prevalence of OSAHS in the Omani population. The aim of the study is to evaluate the association of BMI, age, and gender difference with prevalence of OSAHS in the Omani population.
This study was conducted for the first time in the Omani population to understand the relationship between OSAHS and the two main risk factors, age and obesity. The study was conducted on a clinic-based population sample at Sultan Qaboos University Hospital, Oman, and was done as part of the sleep medicine audit in Oman.The main outcome of analysis was that having AHI >15 is differently related to gender; in men, it is related to BMI and not age, on the contrary, in women, it is related to age and not BMI.
The prevalence of OSAHS of 4% in men and 2% in women estimated by Young et al. was based on an AHI score of 5 or higher and moderate to severe daytime hypersomnolence. In this study, AHI >15 was implicated as a cut-off point for OSAHS and the results showed that 49% of the study sample had obstructive sleep apnoea, with higher prevalence among men (57%) compared with women (33%). A limitation of this study is that the study sample was hospital-based and may therefore have selection bias. In addition, daytime sleepiness was not assessed by a validated scale or questionnaire, e.g. the Epworth Sleepiness Scale, which could be a further limitation of this study. However, this study confirmed that there is a gender difference in the association of OSAHS with age and BMI. AHI correlated significantly with BMI, but not with age, in men. On the contrary, AHI in women showed a significant correlation only with age with a four-fold increase in risk for women older than 60 years of age compared to women under 40. These findings could be attributed to the lower levels of sex hormones, especially progesterone, which occurs in post-menopausal women. The association of reduced female sex hormones with an increased probability of obstructive sleep apnoea in women is well documented.Previous studies found that those women with an AHI >10 had significantly lower levels of 17-OH progesterone, progesterone, and estradiol than those with an AHI less than 10.12 Similar results were found by Redline et al. who found in a community study that females with OSAHS were significantly older (P <0.01) than apnoeic male subjects and the majority of those females were postmenopausal.However, they found no significant difference in BMI between the two genders.Furthermore, Young et al. found that postmenopausal women had a higher odds ratio of having AHI >15 compared to perimenopausal women (perimenopause: 1.1versus postmenopause: 3.5 .
Our results were in accord with the increasing prevalence of obesity and metabolic syndrome in the Omani population. Al-Lawati et al. found that the prevalence of metabolic syndrome increased with age in both sexes, but the increase was steeper in women.Furthermore, in the age group 2029 years, 4.7% of men and 2.8% of women had metabolic syndrome. In the age group 60 years and over, the prevalence was 29.8% and 48.7%, respectively. In Duráns study, a strong association between AHI and age was found in the logistic regression model adjusted to sex and BMI, suggesting that factors other than obesity play a role in the presence of OSAHS.When AHI for men and women were pooled together, there was significant correlation with age and BMI. The results indicated that obesity is the main risk factor for OSAHS in Omani men with increasing risk with higher BMI. Similar results were found by Young et al. who found that male sex, age and BMI were strongly associated with AHI >15.15 A study by BaHammam et al. found that the prevalence of obstructive sleep apnoea among middle-aged Saudi women (3560 years) was 40%.However, the population sample was screened using the Berlin questionnaire only and found no correlation with age. It was shown in an urban Indian population that, when BMI was normal, metabolic syndrome may be the first event, followed by OSAHS as age increases and eventually it may culminate in syndrome Z (OSAHS and metabolic syndrome together). More recently, it was found that metabolic syndrome prevalence, including obesity is associated with increased severity of OSAHS.
Conclusion
This study revealed gender difference in associations of sleep disordered breathing in an Omani population. Male gender and obesity led to higher risk compared to women in the same age group. However, age is the major predictor for obstructive sleep apnoea among women, with a higher risk of OSAHS in postmenopausal woman.
Credits: Mohammed Al-Abri,Khamis Al-Hashmi,Deepali Jaju,Omar Al-Rawas,Bazdawi Al-Riyami,and Mohammed Hassan.Department of Physiology, Sultan Qaboos University Hospital, Muscat, Oman
More Information:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3210046/?tool=pubmed