Does personality play a role in continuous positive airway pressure compliance?

Obstructive sleep apnoea (OSA) is a condition characterised by repetitive, intermittent partial or complete collapse/obstruction of the upper airway during sleep. During wakefulness, dilator muscles contract during inspiration to maintain airway patency. This prevents collapse as a consequence of suction during inspiration. However, during sleep, the tone of these muscles falls, causing narrowing or total obstruction of the airway.

Continuous positive airway pressure (CPAP) is highly efficacious in treating OSA but its effectiveness is limited due to suboptimal acceptance and adherence rates; 5–89% of patients will reject CPAP as a treatment immediately, 25–50% of patients who commence treatment will fail to continue [1–4], 50% will discontinue CPAP treatment within 1 year [5] and 25% terminate CPAP treatment within 3 years [1]. This large prevalence of nonadherence decreases its effectiveness, and is limited in improving daytime sleepiness, mental and physical health, and cognitive functioning [1, 6]. These nonadherence numbers are similar to other populations with health concerns, where roughly 20–40% of individuals with acute illness, 30–60% with chronic illness and 50–80% of those using preventative care are nonadherent to their prescribed medical treatment [5].

Research has focused on finding common qualities and/or circumstances that may lead to nonadherence, such as age, sex, race, apnoea hypopnea index (AHI), body mass index (BMI) and education levels, but these have been inconclusive, equivocal or confounded by other demographic variables [1, 4]. Therefore, more recent research has focused on the psychosocial and personality traits that may contribute to noncompliance, shifting the focus of patient treatment from socioeconomic, physical and environmental predictors to that of more stable personality factors [1, 2, 5].

Aikens et al. [7] evaluated patients with OSA using the Minnesota Multiphasic Personality Inventory (MMPI), and discovered that 58% of these patients demonstrated at least one MMPI elevation and 38% had two or more, with depression, hypochondriasis and hysteria being the highest. From this study, it was reported that those with core depressive symptoms on the MMPI had less severe OSA, and those with a diverse set of psychological symptoms stronger than depression had a greater AHI and lower oxygen saturation [7]. Depressive symptoms and anxiety are often seen in patients with OSA, which worsens fatigue, but CPAP decreases fatigue providing significant improvement in depression and anxiety [8]. OSA patient satisfaction with CPAP treatment positively correlates with adherence, with the greater the day to day improvement noticed the greater the likelihood of using CPAP [9].

Personality traits of treatment noncompliers

Several studies have used personality type indicator measures (e.g. MMPI and Big Five) to investigate individuals with varying degrees of OSA. Type D personality appears to be prevalent in 30% of the OSA population, in contrast to only 13–24% in the general population [3, 5, 6, 9] according to several studies conducted in the USA, Sweden, Belgium, Canada, Germany and the Netherlands. Type D personality is characterised by two traits:

• negative affectivity, which is the tendency to experience negative emotions; and

• social inhibition, the hindering of emotional and behavioural expression for fear of rejection or disapproval by others [4–6, 9].

Type D is a predictor of poor health status and increased risk of mortality in other medical conditions (e.g. chronic pain, mild traumatic brain injury and asthma) [9]. Type D has been linked to certain negative behaviours such as an unhealthy lifestyle, reluctance to consult or follow medical advice, and poor treatment outcomes, adversely affecting the clinical course of medical conditions and treatment compliance [9]. Type D personalities are more likely to be anxious, depressed, socially inhibited, have a decreased quality of life and suffer increased psychological distress [1, 3, 6, 9, 11]. OSA patients with Type D personality have poor medication compliance, and lower adherence to CPAP and mandibular advancement devices (MADs) than those who are not Type D [3, 6]. Roughly 50% of Type D OSA patients use their CPAP for <4 h per night, unlike their non-Type D counterparts who use their CPAP for 6 h a night; 45% also discontinue MAD treatment [3, 5, 6]. Type D personalities are more likely to have medical comorbidities, a decreased personal view of their own health, decreased physical functioning and poor psychosocial functioning [9]. Their subjective perception of the problem does not always adequately reflect the actual severity of the condition, and they report side-effects of CPAP more frequently (e.g. dry throat and mask leaks) [1, 3, 9]. Type D decreased adherence to CPAP may also be caused by decreased perceived effects of the treatment and low self-efficacy [3].

When compared to those with snoring, OSA patients have significantly higher absolute scores on the hypochondriasis, psychopathic deviance and depression scales of the MMPI [1, 11]. Scores high on the depression and hypochondriasis scales also predict low CPAP adherence [16]. The hypochondriasis scale measures an over-concern with one’s state of health [4] and high scores indicate extreme attention to physical symptoms, chronic fatigue and weakness, and noticing vague symptoms, which lead to higher rates of noncompliance [11]. High scores on the hypochondriasis scale also influence subjective daytime sleepiness [12]. High scores on psychopathic deviance may show difficulty adhering to rules and following the advice of authority figures/medical staff, and failing to learn from past mistakes, again increasing risk of continual nonadherence [11]. The prevalence rate of depression in OSA compared to people without OSA is roughly 33%, which may be a direct consequence of sleep deprivation or could be an indirect consequence of social effects caused by the disorder [13], as long-term sleep deprivation can adversely affect mood [3]. Individuals with OSA tend to have a higher BMI than the normative population [15] and obesity is associated with an increased risk of depression as well [13].

The personality patterns of OSA patients with low CPAP adherence have been found to be a somatic–neurotic type, consisting of physical symptoms that derive from the psyche more than from a physical illness [11]. This increased somatic development of symptoms creates a high level of psychological distress for the patient, as a consequence of OSA, not as a cause of it [11]. Other factors that increase low adherence to CPAP are OSA patients who exhibit a significantly high level of denial of disease severity, hysterical personality characteristics, decreased physical activity, feelings of guilt, a pessimistic outlook on life and low self-esteem [11]. Individuals with Type D score high on neuroticism, low on extraversion and low on conscientiousness when evaluated using the Big Five personality model, and score high on the BIS, displaying avoidance and aversion to unpleasant stimuli [4, 9]. The higher scores on the BIS are possibly due to fear and anxiety developing with respect to CPAP being an invasive and undeniable long-term treatment [4].

Another factor that could give insight into whether a patient will have low CPAP adherence is knowing who scheduled the patient for treatment. If the patient’s partner refers them, rather than the patient referring themselves, adherence to CPAP decreases [2]. This phenomenon may be due to Type D personalities having a high external locus of control (e.g. believing their health is determined by external forces, not the internal self) or minimising their symptoms, thereby not considering treatment to be necessary [1–3, 15].

Personality traits of treatment compliance

Patients who have a high internal locus of control (e.g. believing they have control over their health) are more likely to adhere to CPAP treatment [1–3, 15]. This is due to internalising and following advice received from sleep specialists, having the ability not to perseverate on treatment side-effects, and displaying high self-efficacy [2]. High self-efficacy empowers individuals to believe in their own ability to deal with obstacles and take control of their own health [5], thus increasing treatment compliance. This also explains why self-referring patients are more likely to adhere to treatment.

Individuals with a high level of conscientiousness and openness, active coping skills, and problem solving traits are also most likely to adhere to treatment [4]. Implementation of coping strategies/skills in demanding situations can lead to a higher overall level of CPAP use per night and continued use over time [2].

CPAP adherence is also increased if a patient is educated on the negative health outcomes that will develop as a result of not using the treatment, as well as believing they have a more severe form of the disorder [2]. Physiological measures of disease severity rarely accurately predict >10% of the variance in adherence [1] but the patient’s belief that his/her OSA is severe will lead to higher treatment compliance.

Those who comply more with CPAP tend to have a higher BMI, report less daytime sleepiness, report better nocturnal sleep quality, and score lower on the depression and hypochondriasis scales on the MMPI prior to treatment [16]. These five predictors identify ∼80% of individuals who eventually fail to comply with CPAP treatment as well as 97% of those who comply long-term [16].