From our study, 65.8 % of our non-apneic snorers were supine dependent. Other studies have tried to look at position dependence and snoring in apneic and non-apneic snorers with differing results. Braver et al. [2] found that in a combined group of 20 male apneic and non-apneic snorers, snoring was not influenced by changes in sleep position. Nakano et al. [5] reported that while position dependence was seen in patients with non-apneic snoring, variable results were seen in apneic snorers. A more recent study by Koutsourelakis et al. [1], however, found that position dependence was noted in both apneic and non-apneic snorers. The possible reasons for these variable results are a lack of a standardized definition for position-dependent snoring, which will be further discussed in our limitations, and differences in study design and definitions of apnea. In Braver et al.’s study, no attempt was made to separate non-apneic from apneic snorers before assessing position dependence. The latter two studies did attempt to separate apneic snorers from non-apneic snorers, but, based on the AASM guidelines [4], the AHI criteria used in these studies to define the non-apneic group actually included patients with mild OSA [1, 5]. Our study objectively measured the influence of position dependence on non-apneic snorers, adhering to the AASM guidelines for sleep apnea.

We also found that the higher a patients’ BMI, the more likely they were to be position-dependent snorers. This result, however, is within a sample group of non-apneic patients. Other studies looking at the association of BMI with position in apneic patients found that POSA seemed to correlate with a slightly reduced BMI [4, 15, 18]. In these studies, however, an increased BMI also correlated with an increased AHI or AI. These findings, therefore, corroborate Mador et al.’s [13] findings that patients with less OSA were more likely to be position dependent.

There were a few limitations to our study. One such limitation is the lack of a quantitative definition for position-dependent snoring. This, however, is seen in the majority of the literature looking at position dependence in non-apneic patients. One study defined position-dependent snoring as a >50 % reduction in snoring rate in the lateral position when compared with the supine position [19]. There are, however, no standardized guidelines defining criteria for position-dependent snoring. As such, comparisons made between position-dependent non-apneic and apneic snorers should take this into consideration. Various parameters have been used to measure snoring in the literature. Such methods include snore intensity (decibels), snoring frequency (snores/h), snoring rate (% TST), or duration (seconds or milliseconds) [20]. Our parameter of choice for the measurement of snoring, the snore index, does not give information regarding the loudness or duration of snoring. While the snore index may not be as comprehensive a research tool when compared with other snoring parameters, it confers the advantage of clinical applicability, as it can be easily obtained from sleep polysomnograms and has also been used in other studies [2]. Also, risk factors such as alcohol consumption, ingestion of tranquilizers/sedatives, and smoking, which can influence snoring habits, sleeping quality, and body position during sleep, were not included in this study. Lastly, the only position individually analyzed for position dependence was the supine position. We have especially chosen for this sleeping position, because in the criteria for POSA, sleeping mostly in supine position is also used to define position dependence.

The results of our study potentially have significant implications for the role of positional therapy in non-apneic snorers. As discussed in other chapters of this volume, the effectiveness of positional therapy in patients with POSA has been tested since the 1980s [14–16, 21–23] and compared with other therapeutic approaches [24–27]. Several attempts to decrease the severity of OSA by influencing supine sleep position have been reported and show that positional therapy can reduce AHI to normal values in patients with POSA [15, 16, 21–24]. The tennis ball technique (TBT) was the first technique to be implemented, but several other methods have also been used as positional therapy in POSA [28]. While all these techniques may have been successful at reducing the AHI, its limiting factor was a lack of compliance secondary to discomfort and the occurrence of arousals while turning from one lateral position to the other, thereby disturbing the patient’s sleep quality and sleep architecture [17]. Long-term (6 months) compliance has been reported to be only 10 % [29].