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Title: 1
The AASM 2012 Recommended Hypopnea Criteria Increases the Incidence of 2
Obstructive Sleep Apnea but not the Proportion of Positional Obstructive Sleep 3
Apnea 4
5
Authors: 6
Brett Duce1, 2 BSc (Hons) RPSGT, Antti Kulkas PhD3,5, Christian Langton PhD2, Juha 7
Töyräs2,4,5 PhD, Craig Hukins1 MBBS FRACP 8
9
Affiliations and addresses: 10
1Sleep Disorders Centre, Department of Respiratory & Sleep Medicine, Princess 11
Alexandra Hospital, Ipswich Rd, Woolloongabba, Qld, Australia 12
2Faculty of Science and Engineering, Queensland University of Technology 13
3Department of Clinical Neurophysiology, Seinäjoki Central Hospital, Seinäjoki, 14
Finland 15
4Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland 16
5Department of Applied Physics, University of Eastern Finland, Kuopio, Finland 17
Email address, telephone and fax number of corresponding author: 18
(E) [email protected] 19
(T) +61 7 3176 5751 20
(F) + 61 7 3176 7096 21
22
Financial support: 23
The authors did not receive any financial support to carry out this study. 24
Running Title: 25
Positional OSA & Hypopnea Criteria 26
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27
Disclosure Statement: 28
This was not an industry-supported study. The authors declare no conflicts of interest 29
in relation to this study. 30
31
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Abstract 32
Objective/Background: This study compared the effect of using the 2007 and 2012 33
American Academy of Sleep Medicine (AASM) recommended hypopnea criteria on the 34
proportion of positional obstructive sleep apnea (pOSA). The effect of modifying the 35
minimum recording time in each sleeping position on the proportion of pOSA was also 36
investigated. 37
Patients/Methods: 207 of 303 consecutive patients (91 of 207 were female) undertaking 38
polysomnography (PSG) for the suspicion of OSA met the inclusion criteria for this 39
retrospective investigation. PSGs were scored for both the 2007 AASM recommended 40
hypopnea criteria (AASM2007Rec) and the 2012 AASM recommended hypopnea criteria 41
(AASM2012Rec). For each hypopnea criteria OSA patients were grouped as positional [either 42
as supine predominant OSA (spOSA) or supine independent OSA (siOSA)] or non-positional. 43
Outcome measures such as SF-36, FOSQ, PVT and DASS-21 were compared between the 44
groups. 45
Results: The AASM2012Rec increased the incidence of OSA compared to AASM2007Rec (84% 46
vs 49% respectively). AASM2012Rec increased the number of patients with supine predominant 47
OSA (spOSA) and supine independent OSA (siOSA) but did not change the proportion 48
(spOSA: 61% AASM2012Rec vs 61% AASM2007Rec, siOSA: 32% AASM2012Rec vs 36% 49
AASM2007Rec). OSA patients diagnosed by AASM2007Rec criteria had similar outcome measures to 50
those diagnosed by the AASM2012Rec criteria. The AASM2012Rec increased the proportion of 51
female OSA patients with spOSA and siOSA. A minimum recording time of 60 minutes in 52
each position decreased the proportion of spOSA, but not siOSA, patients when compared to 53
a minimum time of 15 minutes. 54
Conclusions: 55
This study demonstrates that, compared to AASM2007Rec, AASM2012Rec almost doubles the 56
incidence of OSA but does not alter the proportion of OSA patients with pOSA. The 57
proportion of female OSA patients with pOSA however increases as a result of AASM2012Rec. 58
Furthermore, the use of different minimum recording times in each sleeping position can alter 59
the proportion of spOSA. 60
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Keywords: Obstructive sleep apnea, hypopnea definition, positional OSA, proportion, 61
methodology, gender. 62
63
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INTRODUCTION 64
Obstructive sleep apnea (OSA) is a disorder characterized by repeated episodes of partial or 65
complete closure of the upper airway during sleep. The disorder is particularly prevalent in 66
the middle-aged population [1] and is associated with excessive daytime somnolence, 67
reduced quality of life, neurocognitive deficits as well as increased risk of diabetes and 68
cardiovascular disease [2]. The diagnosis of OSA typically involves correlation of clinical 69
symptoms with the Apnea-Hypopnea Index (AHI); a metric derived from polysomnography 70
(PSG) or polygraphy. An interesting feature of OSA is the individual differences in distribution 71
of apneas and hypopneas across the night. While apneas and hypopneas may be ubiquitous 72
across the night in some OSA patients, others show a greater incidence relative to specific 73
sleep states or body positions. Positional OSA (pOSA), also known as supine OSA, is one 74
such OSA phenotype where the AHI is greater while the patient is sleeping in the supine 75
position. This characteristic in some patients has led to the development of positional therapy 76
devices, which encourages the patient to sleep in their best sleep position and is used as 77
either an alternative or a complement to CPAP therapy. 78
79
The proportion of pOSA within an OSA population varies between approximately 25% [3] and 80
60% [4]. This large range has been attributed to the various definitions used to classify pOSA 81
[5]. Early definitions of pOSA used variations of a simple supine AHI to non-supine AHI ratio 82
of 2:1 [6][7]. Of late, definitions of pOSA have tried to differentiate between the presence and 83
absence of clinically significant OSA (AHI >5/h) in the non-supine position [3]. This has led to 84
the classification of two different subtypes of pOSA: supine predominant OSA (spOSA) and 85
supine isolated OSA (siOSA). Supine predominant OSA is usually defined as a total AHI of 86
>5/h and a ratio of ≥2:1 for the supine AHI:non-supine AHI. The more stringent definition, 87
supine isolated OSA (siOSA), is usually defined as a total AHI of >5/h, a ratio of ≥ 2:1 for the 88
supine AHI:non-supine AHI and a non-supine AHI of <5/h [5]. 89
90
The proportion of patients with pOSA could be affected by other factors, such as hypopnea 91
scoring criteria and the minimum time recorded in each position during PSG. Over the years, 92
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a number of hypopnea definitions have been utilized in studies of supine OSA. Studies in 93
pOSA have used either bespoke criteria (such as a 4% SpO2 desaturation or EEG arousal 94
[3]) or one of the standard criteria available such as the Chicago Criteria [8], the AASM 2007 95
recommended (AASM2007Rec) and the AASM 2007 alternate (AASM2007Alt) criteria [9]. Since 96
this time the standard hypopnea criteria have undergone another modification with the AASM 97
2012 (AASM2012) [10] recommended hypopnea becoming the new standard. This standard 98
defines a hypopnea as 30% decrease in flow with an accompanying 3% SpO2 desaturation 99
or EEG arousal. Implementing this criterion has a large impact on the total AHI and the 100
general incidence of OSA [11]. However the impact of transitioning from AASM2007Rec to 101
AASM2012Rec upon the proportion of pOSA in an OSA population is unknown. 102
103
For studies of pOSA, a minimum recording time for supine and non-supine sleeping positions 104
is recommended to ensure that a representative sample of sleep is available to make a fair 105
comparison. In the literature however, it appears that minimum recording times for pOSA 106
studies have been used unevenly. Some studies exploring pOSA have not stated a minimum 107
time in each position in their criteria while others have required a minimum of 15 [3], 20 [12], 108
30 [7] or 60 [13] minutes of sleep in each position for inclusion in their studies. Therefore, 109
while a minimum recording time in each sleeping position is essential, there are no studies 110
that examine how these differences contribute to the varying proportions of pOSA in an OSA 111
population. 112
113
In this study, our primary aim was explore the impact of the AASM2007Rec and AASM2012 114
hypopnea criteria on the proportion of patients with pOSA and their clinical characteristics. A 115
secondary aim of this study was to examine the effect of modifying the minimum time in each 116
sleeping position on the proportion of pOSA in a sleep clinic population. 117
118
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METHODS 119
Patient Selection 120
Data from consecutive patients undertaking diagnostic PSG for the clinical suspicion of OSA 121
during the period of January 2015 to December 2015 were re-analysed for this study. PSG’s 122
were excluded from analysis if less than 2 hours of sleep were recorded, less than 15 123
minutes of sleep was observed in both the supine and non-supine positions, a split night 124
treatment protocol (diagnostic to PAP therapy) was implemented, a primary PSG channel 125
(nasal pressure, pulse oximetry, electroencephalogram, respiratory effort, body position) 126
contained too much artefact for reliable analysis or oxygen was administered at any time 127
during the course of the PSG. The Institutional Human Research Ethics Committee approved 128
this study (HREC/16/QPAH/021). 129
130
Polysomnography 131
PSG’s were recorded with the Compumedics Grael acquisition system (Abbotsford, 132
Australia). The recording montage comprised of electroencephaolgram (EEG, recommended 133
derivation: F4-M1, C4-M1, O2-M1), left and right electro-oculogram (EOG, recommended 134
derivation: E1-M2, E2-M2), chin electromyogram (EMG, mental/submental positioning), 135
electrocardiogram (ECG, modified lead II), nasal pressure (DC amplified), oronasal 136
thermocouple, body position, thoracic and abdominal effort (inductive plethysmography), 137
pulse oximetry, left and right leg movement (anterior tibialis EMG) and sound pressure (dBA 138
meter: Tecpel 332). Body position was recorded using a triaxial accelerometer 139
(Compumedics, Abbotsford, Australia) attached at the midline of the lower sternum. 140
Reliability of the body position recording was confirmed with synchronized digital video 141
recordings and corrected where necessary during the PSG scoring process. 142
143
Outcome Questionnaires and Vigilance Testing 144
Prior to undertaking the diagnostic PSG, patients completed the Epworth Sleepiness Scale 145
(ESS) [14], the Functional Outcomes of Sleep Questionnaire (FOSQ) [15], the Short Form-36 146
quality of life questionnaire (SF-36) [16], and the Depression Anxiety Stress Scale (DASS21) 147
Page 8 of 24
[17]. Patients also completed the 10 minute version of the PEBL Psychomotor Vigilance Task 148
(PVT) [18][19] on an ASUS Transformer Pad with attached keyboard. The patients were 149
instructed to monitor the tablet display and press a response button using the index finger or 150
thumb on their dominant hand as soon as the pink stimulus dot appeared on the screen. The 151
presentation of the next stimulus was programmed to vary randomly between two and ten 152
seconds. 153
154
Polysomnogram Scoring Protocol 155
PSGs were originally scored for clinical use according to the AASM2012 criteria. The PSGs 156
were then de-identified and all previous hypopnea scorings was removed. The PSGs were 157
then randomly presented and re-scored twice for respiratory events; once each using the 158
AASM2007Rec criteria and the AASM2012Rec criteria. Randomization of PSGs was performed 159
using the freely accessible Randomizer website [20] Once each PSG was de-identified, a 160
copy was made of the PSG. Each PSG (including the copy) was assigned a unique number 161
and either the code “07” or “12” to signify what rule set is being used. Thus we had PSGs 162
had an assigned number between 1 and 414, while half of these had the “07” code assigned 163
and the other half had the “12” code assigned. The Randomizer website then provides a 164
randomized list of those numbers to indicate when these PSGs are to be presented. The 165
PSGs for scoring are then renumbered but maintain the “07” or “12” code. The PSGs are 166
then re-scored starting from PSG 1 through to PSG 414. The randomization order is revealed 167
once all studies are re-scored. This process scored only two pairs of PSGs consecutively. 168
Respiratory events were then tabulated to determine AHI and Hypopnea Index (HI) for 169
supine and non-supine sleep in addition to NREM and REM sleep. PSGs were scored with 170
Compumedics Profusion 4.0 (Build 410) software while viewed on Dell P2414H (1920 x 1080 171
resolution) LCD monitors. The PSG scorer (BD) has over 15 years’ experience in scoring 172
PSGs and participates regularly in intra- and inter-laboratory scoring concordance activities. 173
174
pOSA Classification 175
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Patients who met the International Classification of Sleep Disorders third edition (ICSD-3) 176
[21] criteria for OSA were classified as spOSA if the supine AHI was ≥2 times the non-supine 177
AHI. Within this spOSA group, patients were subclassified as siOSA if the non-supine AHI 178
was less than 5/h. All other OSA patients were classified as non-positional OSA (non-pOSA). 179
180
Data and Statistical Analysis 181
Statistical analyses were performed using GraphPad Prism 6.05 (GraphPad Software, La 182
Jolla, CA). The normality of group data collected was determined by the D’Agostino-Pearson 183
omnibus K2 test [22]. Data are presented as median and interquartile range where 184
appropriate. Group data were compared using either unpaired t-test or Mann-Whitney test. 185
The proportion of male:female in each group was compared using a Chi square test. A 2x4 186
contingency table for the proportion of pOSA diagnoses was tabulated for each criterion. The 187
contingency table used the categories of No OSA, non-pOSA, spOSA, and siOSA. The 188
spOSA category in the 2x4 table did not include patients that also met the criteria for siOSA 189
(ie not counted twice). The two hypopnea criteria were then compared at each category 190
using the Freeman-Halton extension of Fisher’s exact test [23]. The effect of recording time 191
on pOSA diagnoses was evaluated by tabulating a 2x3 contingency table and also using the 192
Freeman-Halton extension of Fisher’s exact test. A 4x4 contingency table for categorical data 193
could not be tested with the chi-square test as the data could not meet all the necessary 194
assumptions of the test [24]. A p<0.05 was considered statistically significant. 195
196
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RESULTS 197
Patient Cohort 198
Two hundred and seven out of 303 patients were included for retrospective analysis. 199
Demographic and PSG data for included and excluded patients are presented in Table 1. 200
Excluded patients were significantly older, more obese, had more co-morbidities but were 201
less somnolent than the patients included in this study. The patients included in this study 202
had significantly less fragmented sleep and spent almost an equal proportion of their sleep in 203
the supine and non-supine positions. There were no differences between the two groups with 204
respect to gender distribution. 205
206
Supine and Non-supine AHI Indices 207
The median AHI and HI in the supine and non-supine sleeping positions for each hypopnea 208
criteria are presented in Table 2. When compared to the AASM2007Rec criteria, the 209
AASM2012Rec criteria resulted in a median (interquartile range) percentage increase in AHI of 210
127% (42%, 257%) and 150% (61%, 447%) for the supine and non-supine positions 211
respectively. No change in the ratio of supine to non-supine AHI’s was observed [median 212
(interquartile range) of 3.1 (1.3, 7.1) and 2.6 (1.3, 6.1) for AASM2007Rec and AASM2012Rec, 213
respectively]. 214
215
pOSA Proportion and Characteristics 216
The changes in pOSA classifications between the AASM2007Rec and AASM2012Rec hypopnea 217
criteria are shown in Table 3. Of the 207 patients meeting the inclusion criteria, 49% 218
(102/207) of those attained a diagnosis of OSA according to the AASM2007Rec criteria. In 219
contrast, 84% (173/207) of those patients would attain the same diagnosis according to the 220
AASM2012Rec criteria. The AASM2012Rec criteria diagnosed an extra 71 patients with OSA with 221
57 of these patients classified as pOSA. Of these 71 patients newly diagnosed with OSA, 57 222
were classified as mild OSA while 14 were classified as moderate OSA. Twelve of the 57 223
newly classified mild OSA patients were non-pOSA while all the moderate OSA patients met 224
the criteria for pOSA. There were more patients with spOSA and siOSA according to the 225
Page 11 of 24
AASM2012Rec criteria than according to the AASM2007Rec criteria. However, when considering 226
the spOSA and siOSA patients as a proportion of all OSA patients, there was no difference 227
between the two criteria (spOSA: 61% vs 61% for AASM2007Rec and AASM2012Rec criteria 228
respectively; siOSA: 36% vs 32% for AASM2007Rec and AASM2012Rec criteria respectively). 229
230
The characteristics of patients meeting the criteria for spOSA and siOSA when scored with 231
AASM2007Rec and AASM2012Rec criteria, respectively, are shown in Table 4. Based on 232
hypopnea criteria, there was little difference in the characteristics between the spOSA and 233
siOSA groups. Each group, irrespective of the hypopnea criteria, showed similarities in 234
sleepiness, quality of life, vigilance, depression, anxiety and stress. The only noticeable 235
difference was that the AASM2012Rec criteria increased the proportion of females in both the 236
spOSA and siOSA categories. 237
238
Minimum Recording Times in Sleeping Positions 239
The effect of modifying the minimum recording times for each sleeping position is shown in 240
Figure 1. A change in the minimum recording time in both the supine and non-supine 241
sleeping positions reduced the number of OSA patients that could be assessed for pOSA. 242
According to the AASM2007Rec criteria, the number of assessable OSA patients was reduced 243
from 102 patients to 88 patients and 69 patients for 15 minutes, 30 minutes and 60 minutes, 244
respectively. Similarly, with the AASM2012Rec criteria, the number of assessable OSA patients 245
was reduced from 173 patients to 88 patients and 69 patients for 15 minutes, 30 minutes and 246
60 minutes, respectively. Proportions of REM sleep relative to the total sleep time recorded 247
in that position was also calculated. In our cohort, the proportion of REM sleep in the non-248
supine position was always greater than the proportion of REM sleep in the supine position. 249
250
Changing the minimum recording time from 15 minutes to 30 minutes did not affect the 251
proportion of spOSA and siOSA patients for each hypopnea criteria. Increasing the minimum 252
recording time to 60 minutes however significantly decreased the proportion of spOSA 253
patients but not siOSA patients for both AASM2007Rec and AASM2012Rec criteria hypopnea 254
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criteria. There were no differences in pOSA proportions when comparing between hypopnea 255
criteria for spOSA and siOSA at each minimum recording time. 256
257
258
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DISCUSSION 259
In this study, we investigated the consequence of different hypopnea criteria on the 260
proportion of pOSA in an OSA population. Our results demonstrate that the AASM2012Rec 261
hypopnea criteria increase the total number of patients with pOSA relative to the AASM2007Rec 262
hypopnea criteria. This increased pOSA however disappears when the number of pOSA 263
diagnoses is considered as a proportion of the total number of patients diagnosed with OSA. 264
Our results also demonstrate that modifications to the minimum recording time in each 265
sleeping position can affect the proportion of patients classified as pOSA. 266
267
A number of studies have previously examined the proportion of pOSA patients in a sleep 268
clinic population, using either a spOSA definition [7][12] or the stricter siOSA definition 269
[3][25]. The proportion of spOSA in these studies was approximately half of the OSA 270
population while siOSA was approximately one quarter of the OSA population. Only one 271
study has examined both spOSA and siOSA definitions in the one population [4] and 272
demonstrated proportions of 60% and 32% for spOSA and siOSA respectively. To ensure 273
clarity with the previous literature, we also chose to use both definitions when comparing the 274
role of hypopnea criteria. In our study the proportion of spOSA and siOSA in our OSA 275
population was similar to Joosten and colleagues [4], demonstrating proportions of 61% and 276
32% respectively with the AASM2012Rec hypopnea criteria. However, the proportion of spOSA 277
and siOSA when this hypopnea criteria was used did not change appreciably in comparison 278
to the AASM2007Rec hypopnea criteria. This was an unexpected finding. 279
280
Previous studies have shown that the AASM2007Rec hypopnea criteria are associated with a 281
reduced incidence of OSA [11][26] compared to other respiratory event criteria. It is 282
reasonable to assume that, for clinical sleep laboratories, the transition from AASM2007Rec 283
hypopnea criteria to the AASM2012Rec hypopnea criteria would also increase the number of 284
pOSA patients in their referral population. It is of interest that the number of pOSA patients 285
relative to the total OSA population did not change. A possible explanation for this is that it is 286
likely that two phenomena occur at the same time. The first phenomenon is where the more 287
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sensitive AASM2012Rec hypopnea criteria increase the number of hypopneas in the non-supine 288
position, making the OSA of some patients both less positional and more severe overall. This 289
is supported, in part, by the AASM2012Rec hypopnea criteria generating relatively larger 290
increases in non-supine HI than supine HI. Additional evidence comes from the changes to 291
patient pOSA classification (as outlined in Table 3), where thirteen of the 25 spOSA patients 292
according to AASM2007Rec were classified as non-positional according to AASM2012Rec. The 293
second phenomenon is where the increased sensitivity of the AASM2012Rec hypopnea criteria 294
allows the scoring of supine-related events in patients previously designated as having no 295
OSA under the AASM2007Rec hypopnea criteria. This is supported by our data demonstrating 296
changes to the patients without OSA according to AASM2007Rec, of the 105 patients without 297
OSA according to AASM2007Rec, 57 were now pOSA and only 14 were non-positional OSA 298
according to AASM2012Rec. Furthermore, most of these newly diagnosed pOSA patients had 299
mild OSA, supporting previous studies which demonstrate that pOSA is more predominant in 300
the milder than in more severe categories of OSA [7] 301
302
While the supine and non-supine AHI increased from the AASM2007Rec to AASM2012Rec 303
hypopnea criteria, there were very few differences with respect to patient characteristics and 304
outcomes. For both spOSA and siOSA, AASM2007Rec and AASM2012Rec hypopnea criteria 305
groups showed similar traits with respect to body mass, sleepiness, vigilance, quality of life, 306
depression, anxiety and stress scores. Interestingly, we found that there was an increased 307
proportion of female OSA patients with pOSA when the AASM2012Rec hypopnea criteria were 308
implemented. This could be explained by the phenotypic differences between males and 309
females with OSA. Previous studies have shown that the sleep-disordered breathing events 310
in females are less likely to be apneas [27], have less severe SpO2 desaturations [28], and 311
more likely to present as flow limitation/upper airway resistance syndrome (UARS) events 312
[29] during PSG. Thus it is likely that the reduction in the SpO2 desaturation requirement as 313
well as the inclusion of the EEG arousal into the AASM2012Rec hypopnea criteria would favor 314
an increased proportion of pOSA in females. 315
316
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The demonstrated effect of using different minimum recording times in each sleeping position 317
on the proportion of pOSA is an important one. Throughout the last two decades, studies 318
examining the proportion of pOSA as well the benefits of positional therapy have used 319
different recording time cut-offs for inclusion. This has created some uncertainty when 320
comparing different studies, and raises the question of what constitutes enough time in each 321
sleeping position. In this study, we have shown that it is possible to make direct comparisons 322
between studies using minimum recording times in the range of 15-30 minutes but not with 323
studies using greater minimum recording times such as 60 minutes. Our study has also 324
demonstrated that the proportion of REM sleep was greater in the non-supine position 325
compared to supine position and this relative contribution did not change much with 326
increasing the minimum recording time in each sleeping position. This suggests that supine-327
related indices could be underestimated, since a large proportion of the OSA population 328
displays significant REM-dominance [30]. However, mathematical modelling of the effects 329
sleep stage and position on the overall AHI suggests that reduced REM proportions plays 330
less of a role in AHI underestimation than time in supine position [31]. Our evidence suggest 331
that a standard minimum recording time in each sleeping position for all future studies, 332
preferably a 60 minute period, be implemented. Based on the results it is not necessary to 333
stipulate specific proportions of REM sleep in each sleeping position. 334
335
Our study is not without its limitations. This study examined the population of a single sleep 336
clinic and is subject to referral bias. This referral bias may affect the generalizability of our 337
outcomes to other sleep clinics. In particular, the ethnicity of our patient cohort would be of 338
particular concern. A Korean study has demonstrated that pOSA patients comprise a much 339
greater proportion of their OSA cohort, indicating that pOSA is likely to be more prevalent in 340
Asian population [32]. Our study did not specifically document patient ethnicity but we 341
estimate that over 90% of our cohort was Caucasian. Furthermore, the number of patients 342
included in our study is relatively small compared to the some pOSA studies, such as the 343
study of Mo and colleagues [32]. A small number of patients may provide an underestimation 344
or overestimation of the true proportion of pOSA patients in our clinic population. However, 345
Page 16 of 24
our general pOSA proportions are similar to other previous studies. Another limitation to this 346
study is that the data are from a single night of PSG. There is sufficient evidence to show 347
night-to-night variability impacts the AHI [33] however this variability does not appear to be 348
related to deviations in supine sleeping time [34]. The use of a 2-hour minimum total sleep 349
time for inclusion into the study cohort could also be a study limitation. It could be argued that 350
2 hours of sleep may be insufficient to determine the positionality of a patient’s OSA. In the 351
literature, studies have utilised either 3 hours [4], 4 hours [25,31], or have not mentioned any 352
minimum total sleep time [3,7,35]. In the absence of an agreed minimum total sleep time in 353
the literature, we chose a minimum total sleep time that had some relevance in our sleep 354
laboratory and others. The 2-hour minimum total sleep time is part of our split-night 355
diagnostic to treatment protocol. Secondary analysis of our data however showed that 356
implementation of a 4-hour minimum total sleep time rule reduced the number of included 357
patients by 30 but did not affect the proportions of patients with pOSA in our cohort. A final 358
limitation of this study is that recordings of position in these PSGs were from the trunk only. 359
Studies have shown that head position as well as the trunk position play an important role in 360
the magnitude of the AHI [36]. Thus, there may be patients where the true effect of sleeping 361
position is underestimated. 362
363
Conclusion 364
Our study has shown that the transition from the AASM2007Rec to the AASM2012 hypopnea 365
criteria will increase the number of patients diagnosed with spOSA and siOSA. However this 366
increase corresponds with a similar increase in the number of patients diagnosed with OSA 367
in general, making the proportion of spOSA and siOSA unchanged. The gender-associated 368
proportion of spOSA did change, with spOSA becoming more prevalent in females with the 369
AASM2012 hypopnea criteria. Furthermore, modifying the minimum recording time in each 370
sleeping position can impact the proportion of spOSA and siOSA. Additional studies are 371
needed to examine whether these different pOSA cohorts also demonstrates different 372
outcomes with respect to positional therapy and PAP therapy. 373
374
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473 474
475
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476 Table 1 Patient characteristics of the cohorts according to the inclusion criteria for this study. 477 478 Parameter Included Excluded p value Number 207 96 Age, yrs 55 (44, 64) 61 (52, 69) < 0.01 BMI, kg/m2 32.6 (28.2, 37.6) 37.4 (30.8, 42.9) < 0.01 ESS 10 (5, 13) 7 (4, 11) 0.01 Gender, M:F 116:91 53:43 0.67 Co-morbidities, % of patients Hypertension 40 49 0.14 Hyperlipidemia 27 40 0.03 GERD 22 27 0.31 Depression 21 24 0.46 Type 2 Diabetes 17 31 0.01 Ischemic heart disease 12 23 0.02 TST, min 328 (263, 376) 252 (175, 327) 0.01 Sleep Efficiency, % 72.4 (61.4, 84.5) 57.1 (38.6, 72.1) 0.01 Sleep Stage Proportions, % of TST NREM Total 81.9 (77.5, 86.8) 85.4 (79.5, 91.3) < 0.01 N1 11.4 (6.8, 18.7) 13.6 (7.6, 23.7) 0.22 N2 47.9 (42.2, 56.3) 50.8 (42.3, 60.5) 0.27 N3 17.2 (9.5, 25.7) 13.7 (4.0, 25.4) 0.08 R 18.0 (13.2, 22.6) 14.5 (8.6, 20.4) < 0.01 AHI (AASM2012Rec) 15.6 (6.7, 32.1) 20.6 (9.4, 45.2) 0.10 ArI, events/h 20.1 (13.5, 31.3) 24.7 (14.8, 38.6) 0.10 Proportion of TST in Supine, % 43 (23, 64) 3 (0, 100) < 0.01 479 Values are presented as median (inter-quartile range). BMI; body mass index, ESS; Epworth sleepiness scale, 480 GERD; gastro-esophageal reflux disease, TST; total sleep time, NREM; non-REM sleep, N1; stage 1 sleep, N2; 481 stage 2 sleep, N3; stage 3 sleep, R; REM sleep, AHI; apnea-hypopnea index, AASM2012Rec; 2012 AASM 482 recommended hypopnea definitions, ArI; arousal index, SpO2. 483
484
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Table 2 Apnea-Hypopnea and Hypopnea indices according to sleeping position and hypopnea criteria 485 for the study cohort. 486 487
Parameter Supine p Non-supine p AASM2012Rec AASM2007Rec value AASM2012Rec AASM2007Rec value AHI (/h) 24.0 (12.2, 56.9) 9.2 (2.7, 27.5) 0.001 6.3 (1.8, 21.8) 1.5 (0.2, 7.8) 0.001 NREM AHI (/h) 20.1 (8.1, 57.9) 6.1 (1.1, 25.6) 0.001 4.5 (1.1, 20.9) 3.0 (0.3, 15.7) 0.043 REM AHI (/h) 28.4 (0.0, 55.4) 12.7 (0.0, 41.2) 0.044 6.1 (1.0, 29.0) 1.9 (0.0, 16.1) 0.003 HI (/h) 17.0 (9.1, 35.4) 4.1 (0.8, 13.6) 0.001 6.0 (1.5, 18.3) 0.6 (0.0, 5.4) 0.001 NREM HI (/h) 14.5 (5.7, 34.1) 2.6 (0.0, 12.1) 0.001 4.0 (0.8, 17.6) 0.3 (0.0, 4.1) 0.001 REM HI (/h) 15.0 (0.0, 41.4) 5.5 (0.0, 21.7) 0.003 4.0 (0.0, 21.7) 0.0 (0.0, 7.1) 0.001
488 Values expressed as median (interquartile range). AASM2012Rec, AASM 2012 recommended hypopnea criteria; 489 AASM2007Rec, AASM 2007 recommended hypopnea criteria; AHI; apnea-hypopnea index, HI; hypopnea index, 490 NREM; non-rapid eye movement sleep, REM; rapid eye movement sleep. 491
492
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493 Table 3. Changes to patient pOSA classification between AASM2007Rec and AASM2012Rec hypopnea 494 criteria. 495 496
AASM2007Rec AASM2012Rec Total No OSA Non pOSA spOSA* siOSA
No OSA 34
(16.4%) 14
(6.8%) 16
(7.7%) 41
(19.8%) 105
(50.7%)
Non pOSA 0 (0%)
38 (18.4%)
2 (1.0%)
0 (0.0%)
40 (19.4%)
spOSA* 0 (0%)
13 (6.3%)
12 (5.8%)
0 (0%)
25 (12.1%)
siOSA 0 (0%)
3 (1.4%)
20 (9.6%)
14 (6.8%)
37 (17.8%)
Total 34 (16.4%)
68 (32.9%)
50 (24.1%)
55 (26.6%)
207 (100%)
497 Values presented as number of patients (% of total number of patients). AASM2012Rec, AASM 2012 recommended 498 hypopnea criteria; AASM2007Rec, AASM 2007 recommended hypopnea criteria, spOSA, supine-predominant 499 obstructive sleep apnea; siOSA, supine-independent obstructive sleep apnea; Non pOSA, non-positional OSA. 500 *spOSA proportion does not include patients who meet the criteria for both spOSA and siOSA. Data is statistically 501 significant (p<0.001) according to the Freeman-Halton extension of Fisher’s exact test. 502 503
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Table 4 Characteristics of patients with non-positional OSA (non-pOSA), supine predominant OSA (spOSA) and supine independent OSA (siOSA) according to each hypopnea criteria.
Parameter Non-pOSA spOSA p
value siOSA p
value AASM2007Rec AASM2012Rec AASM2007Rec AASM2012Rec AASM2007Rec AASM2012Rec
Proportion 39% (40/102)
39% (68/173) 0.99 61%
(62/102) 61%
(105/173) 0.99 36%
(37/102) 32%
(55/173) 0.51
Age 55 (43, 65) 56 (43, 65) 0.74 59 ± 13 55 ± 14 0.08 56.4 ± 2.4 52.9 ± 1.9 0.25
Gender (M:F) 25:15 41:27 0.53 44:18 62:43 0.02 26:11 29:26 > 0.01
BMI 39.3 (34.0, 44.0) 36.1 (31.9, 41.9) 0.12 33.1 (28.6, 36.6) 31.7 (28.2, 36.4) 0.29 33.5 (28.7, 36.3) 29.9 (27.0, 33.9) 0.06
ESS 11 ± 5 10 ± 5 0.75 9 ± 5 9 ± 5 0.98 11 (4, 13) 9 (4, 15) 0.99
FOSQ 14 ± 4 14 ± 4 0.94 15 (11, 17) 14 (11, 17) 0.75 13 (11.0, 17) 13 (9, 17) 0.99
SF-36 MCS 35.5 ± 11.8 36.0 ± 11.8 0.85 35.9 ± 12.4 36.0 ± 12.8 0.87 34.5 ± 2.6 34.3 ± 1.9 0.97
SF-36 PCS 35.2 (28.4, 47.7) 40.0 (29.4, 47.7) 0.52 40.2 (34.7, 47.4) 39.1 (32.1, 47.0) 0.54 37.9 (35.5, 46.1) 41.0 (33.4, 46.8) 0.59
1/RT 2.7 ± 0.4 2.7 ± 0.4 0.86 2.6 ± 0.5 2.6 ± 0.5 0.60 2.5 ± 0.1 2.5 ± 0.1 0.95
PVT Lapses 7 (2, 16) 7 (2, 16) 0.98 6 (2, 30) 9 (3, 26) 0.59 10 (4, 40) 9 (4, 20) 0.85
1/Slowest 10% 1.8 (1.3, 2.2) 1.8 (1.3, 2.2) 0.94 1.8 (1.2, 2.0) 1.7 (1.1, 2.1) 0.48 1.6 (1.0, 2.0) 1.7 (1.0, 2.0) 0.81
DASS-21 D 12 ± 10 14 ± 11 0.31 12 (4, 18) 8 (2,18) 0.54 10 (2, 18) 12 (2, 19) 0.70
DASS-21 A 8 (6, 14) 10 (6, 16) 0.64 11 (6, 16) 8 (4, 14) 0.45 11 (6, 17) 8 (4, 15) 0.45
DASS-21 S 12 ± 9 14 ± 9 0.39 13 ± 9 13 ± 9 0.94 12 (6, 20) 12 (6, 20) 0.94
Values presented as mean ± standard deviation or median (interquartile range) where appropriate. spOSA, supine-predominant obstructive sleep apnea; siOSA, supine-independent obstructive sleep apnea; AASM2012Rec, AASM 2012 recommended hypopnea criteria; AASM2007Rec, AASM 2007 recommended hypopnea criteria; BMI; body mass index, ESS; Epworth sleepiness scale, FOSQ; functional outcomes of sleep questionnaire, SF-36 MCS; short-form 36 quality of life questionnaire mental component score, SF-36 PCS; short-form 36 quality of life questionnaire physical component score, 1/RT; PVT reciprocal response time, 1/Slowest 10%; the slowest 10% of the PVT reciprocal response time, DASS-21 D; depression anxiety stress scale depression component score, DASS-21 A; depression anxiety stress scale anxiety component score, DASS-21 S; depression anxiety stress scale stress component score ..
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Minimum Time (min)
AASM2007REC AASM2012REC Number of
OSA Patients
REM Sleep (%) Number of OSA
Patients
REM Sleep (%)
Supine Non-supine Supine Non-
supine
15 102 11 (0, 19)* 17 (5, 26) 173 13 (1, 21)* 18 (7, 27) 30 88 12 (2, 21)* 18 (5, 28) 156 13 (1, 23)* 18 (8, 28) 60 69 13 (2, 20)* 19 (11, 30) 121 14 (2, 23)* 19 (12, 30)
Figure 1 Effect of minimum time in supine and non-supine sleeping positions with determining the proportion of spOSA and siOSA for each hypopnea criteria. (A) Proportion of spOSA and siOSA patients according to the required minimum time recorded in each sleeping position. AASM2012Rec, AASM 2012 recommended hypopnea criteria; AASM2007Rec, AASM 2007 recommended hypopnea criteria; spOSA, supine predominant OSA; siOSA, supine independent OSA. * denotes significance at the p<0.05 level. All other within-group comparisons are not statistically significant. (B) Table presenting the number of OSA patients meeting the required minimum time recorded in each sleeping position and the proportion of REM sleep with each minimum time recorded in each sleeping position. Proportion of REM sleep with each minimum time recorded in each sleeping position is presented as median (interquartile range). * denotes p<0.05 compared to the non-supine proportion of REM sleep for each required minimum time recorded in each sleeping position.
A
B
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Abbreviations
AASM, American Academy of Sleep Medicine;
AASM2012Rec, 2012 AASM recommended hypopnea definitions;
AASM2007Rec, 2007 AASM recommended hypopnea definitions;
AHI, Apnea-Hypopnea Index;
ArI, EEG Arousal Index;
ECG, electrocardiogram;
EEG, electroencephalogram;
EOG, electrooculogram;
EMG, electromyogram;
HI, Hypopnea Index;
LCD, liquid crystal display;
NREM, non-rapid eye movement sleep;
N1, stage 1 sleep;
N2, stage 2 sleep;
N3, stage 3 sleep;
OSA, Obstructive Sleep Apnea;
pOSA, positional obstructive sleep apnea;
PSG, polysomnography;
R, rapid eye movement sleep;
siOSA, supine independent OSA;
spOSA, supine predominant OSA;
