Patients with Sleep Apnea but no Daytime Sleepiness

Abstract & Commentary

Synopsis: Whether patients with a pathologic sleep apnea-hypopnea index without daytime symptoms need to be treated is unclear. Treating these patients with nasal CPAP did not significantly change their quality of life, objective sleepiness, vigilance, attention, memory, information processing, visuomotor coordination, or arterial blood pressure.

Source: Barbe F, et al. Ann Intern Med. 2001;134:1015-1023.

The sleep apnea-hypopnea syndrome is defined by a pathologic number of apneas and hypopneas per hour. This syndrome is known to be associated with arterial desaturation, sleep disruption with arousals, snoring, and excessive daytime sleepiness. This syndrome is most commonly treated with nasal continuous positive airway pressure (CPAP), resulting in improvement in daytime symptoms. It is unclear, however, whether patients with an elevated apnea-hypopnea index (AHI) without daytime symptoms need to be treated. This study evaluates the short-term effects of CPAP on quality of life, objective sleepiness, cognitive function, and arterial blood pressure in these patients.

Barbe and colleagues conducted a prospective, multicenter, randomized, placebo-controlled, parallel group study in which 55 patients with an AHI of 30 or higher, Epworth Sleepiness Scale of 10 or less, and no to mild daytime symptoms were randomly assigned to either nasal CPAP or sham CPAP. All patients underwent a polysomnographic study (PSG) to record the AHI. All patients also were evaluated for: 1) quality of life as measured by the Medical Outcomes Study 36-Item Short-Form Health Survey and the Functional Outcomes of Sleep Questionnaire; 2) degree of sleepiness as measured by the Multiple Sleep Latency Test and Epworth Sleepiness Scale; 3) psychological variables including attention, vigilance, visual memory, coordination, and mental control as assessed by the Wechsler Adult Intelligence Scale, Wechsler Memory Scale, the Paced Auditory Serial Addition Test (PASAT), and the trail making test; 4) arterial blood pressure; and 5) drug intake. The optimal CPAP setting was determined during an overnight PSG. Adherence to the CPAP or sham CPAP was assessed by patient report and a built-in timer.

Of the initial 69 eligible patients, 55 entered the study. Of these, 29 were assigned to CPAP treatment and 26, of which 1 was lost to follow-up, were assigned to sham CPAP. There was no significant difference in the baseline data or clinical characteristics between the groups. The results on the objective measures of quality of life, daytime sleepiness, and psychological analysis were not significantly different between the 2 groups. Assessment of these variables after 6 weeks of CPAP or sham CPAP revealed that there was no significant change in these variables. There was only a small absolute difference in the scores of the PASAT, which was statistically significant (P = 0.04). The clinical significance of this small difference in PASAT, however, is unclear.

Barbe et al conclude that after 6 weeks of treatment with nasal CPAP in those with increased AHI but without daytime symptoms, there was no significant improvement in terms of quality of life, subjective and objective sleepiness, cognitive function, or arterial blood pressure. Therefore, Barbe et al do not support the use of active treatment with CPAP in such patients. However, they do recommend periodic follow-up of these patients as progression of disease is possible and these patients may develop symptomatic disease in the future at which time treatment would be required.

Comment by Dheeraj Khanna, MD, Arunabh, MD, and David Ost, MD

The obstructive sleep apnea-hypopnea syndrome (OSAHS) is characterized by a reduction in (hypopnea) or complete cessation of (apnea) airflow despite inspiratory efforts and symptoms of excessive daytime somnolence.1 Treatment of OSAHS is usually with nasal CPAP. Nasal CPAP is effective in improving daytime sleepiness, cognitive function, psychological well-being, and daytime function.2 This treatment is used in patients with a pathologic AHI, defined as an AHI > 5,1 and symptoms of excessive daytime somnolence.3

The American College of Chest Physicians consensus statement recommends treatment with CPAP for: 1) all patients with OSAHS with an AHI > 30 regardless of symptoms and; 2) those with an AHI of 5-30 with symptoms of excessive daytime sleepiness, impaired cognition, mood disorders, insomnia, or documented cardiovascular diseases (including hypertension or ischemic heart disease).3 Whether patients with mild disease should be treated is controversial. Mild disease can be defined as an AHI of 5-30 with symptoms of mild hypersomnolence. These include unwanted sleepiness or involuntary sleep episodes during sedentary activities (watching TV, reading, traveling as a passenger).1 Engleman and colleagues reported that even patients with mild OSAHS could benefit from CPAP.4 However, whether patients with an elevated AHI without symptoms would also benefit has not been well studied.

The investigation study shows that patients with an AHI in even the severe range do not benefit from CPAP over the short-term if they do not have evidence of daytime symptoms. The study may have been limited by its small sample size and, therefore, may not have been able to detect small but clinically significant differences. Further, it is difficult to evaluate for improvement in symptoms that are minimal to begin with. This study also found that there was no improvement in blood pressure with CPAP treatment. Again, these patients did not have hypertension, therefore, it would probably be unlikely that an improvement would be observed. In addition, a longer follow-up period may be needed to gain the full benefits of treatment in terms of impact on blood pressure control. Future studies may need to examine patients with hypertension, pathologic AHI without daytime symptoms over a longer period of follow-up to determine if there is any physiologic benefit from treatment of asymptomatic OSAHS.

Dr. Khanna has a Fellowship in Pulmonary, Critical Care, and Sleep Medicine, North Shore University Hospital. Dr. Arunabh is an attending in the Division of Pulmonary and Critical Care Medicine, North Shore University Hospital, Manhasset, NY.

References

1. Report of an American Academy of Sleep Medicine Task Force. Sleep. 1999;22:667-689.

2. Engleman HM, et al. Thorax. 1998;53:341-345.

3. Loube DI, et al. Chest. 1999;115:863-866.

4. Engleman HM, et al. Am J Respir Crit Care Med. 1999;159:461-467.