A Matched Comparison of MMPI Responses in Patients with Primary Snoring or Obstructive Sleep Apnea

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1 MATCHED COMPARISON OF MMPI RESPONSES A Matched Comparison of MMPI Responses in Patients with Primary Snoring or Obstructive Sleep Apnea James E. Aikens, Ph.D. and Wallace B. Mendelson, M.D. University of Chicago, Chicago, IL Summary: Study Objective To compare the MMPI responses between nonapneic primary snoring (PS) and obstructive sleep apnea (OSA). Design Cross sectional with matched samples. Setting University sleep disorders center. Patients All PS patients (n=49) available in a series of 428 clinical referrals to a sleep disorders center, and age and gender-matched OSA patients (n=49) selected from the 199 available OSA patients in the series. Interventions Not applicable. Measurements and Results Subjects completed the MMPI prior to overnight diagnostic polysomnographic assessment and multiple sleep latency test (MSLT). OSA patients exhibited a mean of 2.3 elevated MMPI scales, which was significantly more than the PS mean of 1.6 elevations, and attributable to higher OSA scores on Depression (D) and Hypochondriasis (Hs). Approximately twice as many OSA patients than PS patients showed disturbed scores on D (49% vs. 25%, p<.05) and Hy (35% vs. 16%, p<.05). On nine of the ten MMPI clinical scales, both patient groups exceeded the elevation rate expected in nondistressed individuals. Among OSA patients, but not PS patients, number of MMPI elevations had a significant negative correlation with sleep efficiency and average blood saturation during NREM, and a significant positive correlation with wake time after sleep onset. Conclusions Compared to patients with PS, those with OSA have more intense depressive symptoms (e.g., pessimism, inactivity, guilt) and somatic concerns. General psychopathology is associated with blood oxygen saturation only among OSA patients. Nonetheless, PS patients show psychological maladjustment that is qualitatively similar, but quantitatively less severe, than that characterizing OSA. Key words: MMPI;, primary snoring; obstructive sleep apnea; depressive symptoms; somatization; psychopathology; arterial oxygen saturation IT HAS CONSISTENTLY been demonstrated that patients with obstructive sleep apnea (OSA) have more intense depressive symptoms than individuals who are free of sleep disorder. 1-3 In OSA patient samples, depressive symptoms are associated with decreased REM activity and increased REM latency, 1 while past depression treatment predicts a higher number of disordered breathing events during both REM and NREM. 4 Several studies have documented depressive symptoms as well as a variety of other types of disturbance in OSA patient samples using the Minnesota Multiphasic Personality Inventory (MMPI), 5 a well-validated 550-item measure with ten clinical scales spanning a wide variety of Accepted for publication February 1999 Comments and Reprint Request to: James E. Aikens, Ph.D.; Director, Behavioral Medicine Service; Department of Psychiatry; University of Chicago Hospitals; 5841 S. Maryland, MC-3077; Chicago, IL , USA. psychiatric symptoms and maladaptive personality features. OSA patients exceed normals on at least five MMPI scales, most prominently Depression (D), Schizophrenia (Sc), and Hypochondriasis (Hs), 6 with higher Hs and Hysteria (Hy) scores than narcoleptics 7 but no differences from patients with assorted disorders of initiating and maintaining sleep. 8 A recent large study of 178 OSA patients 9 documents that 58% of OSA patients have at least one elevated MMPI scale, with an average of 1.8 elevations and the highest scores on Depression (D), Hs, and Hy. This study also indicates that an average arterial oxygen saturation (asleep) < 92% is associated with a higher number of elevations as well as with absolute scores on six of the ten MMPI scales. The probable etiological role of respiratory disturbance in these psychopathology associations is suggested by the finding that psychopathology improves at least partially after medical or surgical treatment of OSA. 2,6,10 SLEEP, Vol. 22, No. 3,

2 In contrast to the relative abundance of OSA data, only a few studies consider the psychological correlates of primary snoring (PS) in the absence of OSA. One study found that PS patients are just as likely to have been treated for depression in the past as OSA patients. 4 However, most of the remaining PS studies emphasize neurocognitive function and only indirectly address the issue of psychological problems. Although PS patients demonstrate more slow wave sleep and fewer sleep stage changes than OSA patients, relative to normals they show deficits in focused attention, 11,12 and fine motor control, 11 and possibly a greater frequency of nightmares. 13,14 While children with PS show reduced hyperactive behavior and better vigilance performance after adenotonsilectomy, 15 a double-blind crossover trial of nasal oxygen therapy failed to alter cognitive function in adult PS males. 16 In summary, aside from a few studies regarding past depression treatment, neurocognitive function, and nightmare frequency, no existing research examines psychological disturbance in PS. We thus compared the MMPI responses of PS patients to those of age and gendermatched OSA counterparts. Our objective was to test our hypothesis that PS is associated with less disturbance than OSA, but greater disturbance than that seen in normal populations. METHODS Subjects Ninety-eight subjects were selected from 499 patients who consecutively underwent overnight diagnostic polysomnography (PSG) after clinical referral to a university sleep disorders center. From the pool of 428 (86%) patients with useable MMPI data, we studied all 49 of those diagnosed with PS. PS diagnosis was based on demonstration of AHI between 1.0 and 4.9 while undergoing PSG for suspected OSA (based on clinical examination in the sleep disorders center). For each PS patient, we selected an OSA counterpart (randomly selected from those with same age and gender) from the 199 eligible OSA patients available in the original clinical series. OSA diagnosis required polysomnographic findings of at least five episodes of either apnea or hypopnea (>10 second duration) per hour of sleep accompanied by oxygen desaturation of >8% (for hypopneas). The 49 selected OSA patients were similar to unselected OSA patients in age (p=ns), although they were more likely to be male (p<.05). The pooled study sample was 77% male, averaged 48 years of age (SD=+13), and had a mean body mass index (BMI) of 33.1 (+12.0). Procedures Subjects independently completed a sleep habit questionnaire and the MMPI, were interviewed by a psychiatrist blinded to MMPI data, and then underwent overnight 12- channel diagnostic PSG followed by 4-trial multiple sleep latency test (MSLT) the next day. Data analysis To judge group differences on continuous variables, we used paired-samples t-tests, with the exception that the nonparametric Wilcoxan signed-ranks test was used to evaluate continuous variables having non-normal distributions (as indicated by skewness index >.4). The McNemar test was used to evaluate group differences on dichotomous categorical variables. Finally, binomial tests were conducted to determine whether observed sample MMPI elevation rates differed from expected rates. RESULTS PSG Variables Sleep and respiratory data varied in the manner that would be anticipated on the basis of diagnostic group (see Table 1). PSG variables used for diagnosis or were outside the focus of this study were not statistically analyzed. OSA patients demonstrated significantly lower mean MSLT latency than PS patients (Matched samples t = 2.52, p<.01). Table 1. Means (SD) for overnight PSG variables and daytime MSLT. PS (n=49) a Sleep History Questionnaire and Interview Data OSA (n=49) b Sleep latency 18.3 (25.5) 17.3 (30.8) Total sleep time 335 (84) 336 (80) Sleep efficiency 76.2 (15.4) 79.7 (16.4) Wake time after sleep onset 77.4 (48.1) 66.5 (56.0) Apnea-hypopnea index 3.0 (5.8) 55.2 (37.2) Mean blood oxygen 92.1 (5.4) 91.0 (6.3) Minimum blood oxygen > (14.3) Mean MSLT latency 10.6 (5.2) 7.8 (5.5) NOTE: All time and latency variables given in minutes. a. 1.0 < AHI < 4.9. b. AHI > 5. Consistent with the observed difference in MSLT latency, more OSA than PS patients reported excessive daytime somnulence (EDS) on the sleep history questionnaire (75% vs. 29%; p<.05). However, there were no significant differences in the presence of self-reported headache, memory deficit, or history of treatment for either depression or any psychiatric problem (all ps=ns). SLEEP, Vol. 22, No. 3,

3 Magnitude of MMPI Clinical Scale Scores We initially compared group means on MMPI clinical scales. Non-K-corrected scores were analyzed, because most prior studies focus on these scores, and mean K levels neither suggested any obvious defensiveness nor differed by group (Mn=56.2 and 53.5 for PS and OSA respectively; t=1.61, p=ns). OSA patients had a mean D score of 68.4, which was significantly higher than the PS group's mean D score of 64.2 (Wilcoxan signed-ranks test Z=1.78, p<.05). The OSA group also scored higher on Hs (Z=1.74, p<.05). There were no other group differences in clinical scale means (all ps=ns). (See Table 2) Rates of MMPI Scales in Disturbed Range In addition to considering MMPI clinical scale group means, we dichotomously classified each individual subject in terms of whether or not each scale fell in the clinically elevated (disturbed) range. Elevation was defined as T score > 70. This idiographic strategy provides different information than group mean profiles, and is somewhat more consistent with the intent of MMPI norm-referenced interpretative procedures. 17 OSA patients had a mean of 2.3 MMPI elevations, which was significantly greater than the PS group mean of 1.6 elevations (Z=1.78; p<.05). As seen above for absolute scores, group differences emerged on D and Hy, but no other scales. Specifically, more than twice as many OSA than PS patients fell into the disturbed range on scale D (49% versus 25%, McNemar statistic p<.05) and on scale Hy (35% versus 16%, p<.05). The norm-referenced T score cutoff of 70 corresponds to two standard deviations above the MMPI normative sample mean, or the 95th percentile of "nondisturbed" individuals. Accordingly, 5% of normal individuals would be expected to score in the elevated range on any given MMPI scale. Binomial tests indicated that for both OSA and PS patients, nine of the ten MMPI scales were elevated for significantly more than 5% of subjects (all ps<.05). Social introversion was the only scale that was not elevated more frequently than the rate expected for normals. Correlates of MMPI Responses For PS patients, there were no significant correlations detected between the MMPI elevations (T>70) and sleep indices. However, within the OSA group, a higher total number of MMPI elevations was significantly associated with shorter total sleep time, lower sleep efficiency, greater wake time after sleep onset, and lower average arterial oxygen saturation (all r s>.37, all ps<.01). MMPI responses were not correlated with sleep latency, AHI, absolute minimum arterial oxygen saturation, or MSLT latency. (Table 3) Table 2. Means (SD) and percentage of sample elevated (T>70) for MMPI clinical scales. PS (n=49) OSA (n=49) MMPI clinical scale Mn+SD % elev'd a Mn+SD %elev'd a Hypochondriasis b 62.8 (8.1) (10.7) 34.7 Depression b 64.2 (13.5) (13.0) 49.0 Hysteria 63.4 (11.6) (11.4) 26.5 Psychopathic deviate 59.3 (11.7) (14.2) 26.5 Masculinity/femininity 57.5 (13.0) (11.1) 14.3 Paranoia 56.3 (10.2) (11.2) 12.2 Psychasthenia 60.0 (12.0) (11.2) 22.4 Schizophrenia 59.8 (12.0) (14.7) 23.4 Hypomania 55.2 (10.9) (11.4) 12.2 Social introversion 53.8 (9.9) (9.4) 10.2 Any scale Number of elevations 1.6 (2.2) (2.4) a All elevation rates (except for Social introversion in both groups) are significantly > 5%. b OSA is significantly > PS on mean score. Table 3. Correlations between PSG variables and total number of MMPI elevations. DISCUSSION Correlation with number of MMPI elevations PS (n=49) OSA (n=49) Sleep latency Total sleep time * Sleep efficiency * Wake time after sleep onset * Apnea-hypopnea index Mean blood oxygen * Minimum blood oxygen Mean MSLT latency NOTE: All time and latency variables given in minutes. This is the first published study of psychological disturbance in PS versus OSA. Our matched comparison of MMPI responses indicates that OSA is characterized by greater psychological disturbance in OSA than in PS. This was evidenced in three critical areas: (1) total number of MMPI elevations; (2) D and Hs absolute scores; (3) and D and Hs elevation rates. Specifically, OSA patients have significantly higher absolute scores and approximately twice the rate of clinical elevation on both D and Hs. This pattern suggests that OSA patients have relatively more inactivity, anergia, guilt, pessimism, and low self-esteem accompanied by prominent somatic concerns. Even though PS patients exhibited relatively less psychopathology than OSA patients, both groups showed higher rates of disturbance than the large MMPI normal reference sample. We thus conclude that PS patients may experience psychologi- SLEEP, Vol. 22, No. 3,

4 cal maladjustment that is qualitatively similar, but quantitatively less severe, than that characterizing OSA. In line with existing data on PSG and neurocognitive impairment, our findings seem to locate PS roughly midway along a general continuum between OSA and normalcy in terms of symptoms and complications. Whether this is a pure reflection of degree of sleep disorder severity or due to some additional accompanying chronic medical illness is a question for subsequent research. Interpretation of the particular set of MMPI elevations differentiating OSA from PS patients is somewhat complicated by the known presence of organic disease. The fact that OSA patients were studied prior to diagnosis and specific OSA treatment, introduces the possibility that Hs elevations are at least a partial artifact of organic disease. Indeed, some of the more vague and diffuse somatic consequences of OSA (e.g., fatigue, low energy, weakness, headache) are transdiagnostic with somatization disorder. Future research is needed to clarify whether OSA patients may have a tendency to develop maladaptive hypochondriacal responses that are not explained by the mere presence of OSA. The most useful future studies will be those which comprehensively assess psychological and psychiatric status before and after applying validated OSA and PS treatments. MMPI elevations only correlated with PSG data among OSA patients. This correlational pattern was such that a higher total number of MMPI elevations was significantly associated with lower sleep efficiency, lower average blood saturation during NREM, and greater wake time after sleep onset (all ps<.05). In our prior larger study of MMPI correlates of OSA parameters, 9 we found that average arterial oxygen saturation (during both REM and NREM) also correlates negatively with total number of MMPI scales as well as six of the ten scales, and that these associations are not attributable to body mass index (BMI). Although the present study yielded a much higher scale D elevation rate (49%) than our prior work (32%), the current sample is biased towards an overrepresentation of males as a function of our PS patient matching procedure. Certain research limitations should be noted. Although the study focused on the differences between PS and OSA, MMPI normative data served as a proxy for a matched sample of healthy individuals. Second, the MMPI measures self-reported traits and behaviors, and does not by itself yield a definitive psychiatric diagnosis. The possibility that a comorbid medical illness, (e.g., hypertension or cardiac disease) also affected MMPI responses needs to be ruled out in subsequent studies. After these data were collected, the MMPI underwent a substantial revision process, resulting in the recent release of the MMPI-II. With updated items and renorming, the new measure may provide a more valid estimate of psychopathology in medical populations. Another potential limitation was that PSG was only conducted for one night, raising the possibility that first night effects may have distorted total sleep time or other parameters. However, first night effects appear to be negligible in OSA, except with respect to sleep efficiency. 18 Clinicians evaluating sleep and breathing disorders should remain aware that although PS is less likely than OSA to be accompanied by depression or impairing somatic concern, both patient groups show suspicious rates of psychological disturbance. Careful psychiatric screening and psychological testing could help ascertain these possibilities. Future research should aim to define the nonmedical factors that influence an individual's definition of his/her own snoring as problematic and requiring medical treatment, considering variables such as subjective distress level, perceived snoring, daytime functioning, nightmares, sleeping partner reports, and the like. 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