Polysomnographic respiratory abnormalities in asymptomatic individuals

Abstract

Study objectives: Polysomnographic respiratory abnormalities have been extensively studied in the general population, but studies have not targeted completely healthy individuals. We aimed to (1) define the frequency of respiratory disturbances (RDI: events per hour of sleep) during sleep in healthy individuals using current techniques and criteria and (2) determine how these abnormalities change with age and sex.

Design and setting: Cross-sectional analyses of RDI in healthy volunteers.

Participants: One hundred sixty-three individuals (106 men) were screened for chronic medical illness, as confirmed by extensive questionnaires, physical examination, electrocardiography, and laboratory analysis. Obese subjects (body mass index > 30 kg/m2) and subjects taking medications were excluded. INTERVENTIONS, MEASUREMENTS AND RESULTS: Subjects underwent full polysomnography using current standard recording and scoring techniques. There was a remarkable increase in RDI with age, particularly over 50 years. Ninety-five percent of currently healthy subjects under 50 years of age had an RDI <15, whereas 50% of subjects older than 65 years had an RDI <15. Men had a higher RDI (median 10) than women (median 5). The effect of age on RDI was similar in men and women.

Conclusions: RDI increases with age even in healthy individuals without symptoms or signs of obstructive sleep apnea syndrome. We do not know whether these individuals will develop pathophysiologic consequences over time or whether this increase with age reflects a normal aging process. If the former, treatment should be considered regardless of symptoms. If the latter, the criteria for treatment should be adjusted by age.

Figures

Figure 1

Scatter plot of the respiratory disturbance index (RDI: events per hour of sleep) by age (years) of men and women. Upper panel, all subjects: the distribution has a similar pattern in men and women, with a dramatic increase in RDI after age 50. There is a similar effect of age in the subgroup of nonsnoring, nonsleepy, nonoverweight subjects (lower panel).

Figure 2

Cumulative relative frequency of respiratory disturbance index (RDI: events per hour of sleep; upper plot) and minimum arterial oxyhemoglobin saturation recorded overnight (%: lower plot) according to age group. More than 95% of the subjects younger than 50 had an RDI

Figure 3

Cumulative relative frequency distributions of respiratory disturbance index (RDI: events per hour of sleep; upper plot) and minimum arterial oxyhemoglobin saturation recorded overnight (%: lower plot) in men and women. Women had an overall lower RDI and less severe desaturation than men, although the shapes of the distributions were similar.