Dissociation of obstructive sleep apnea from hypersomnolence and obesity in patients with stroke

Abstract

Background and purpose: Obstructive sleep apnea (OSA) is seldom considered in the diagnostic investigation in the poststroke period although it is a stroke risk factor and has adverse prognostic implications after stroke. One reason might be that widely used clinical criteria for detection of OSA in the general community are not applicable in patients with stroke. We hypothesized that patients with stroke report less sleepiness and are less obese than subjects from a community sample with the same severity of OSA.

Methods: We performed polysomnography in 96 consecutive patients with stroke admitted to a stroke rehabilitation unit and in a community sample of 1093 subjects without a history of stroke. We compared the degrees of subjective sleepiness assessed by the Epworth Sleepiness Scale and body mass index between the 2 samples according to OSA categories assessed by the frequency of apneas and hypopneas per hour of sleep (<5, no OSA; 5 to <15 mild OSA; and >or=15, moderate to severe OSA).

Results: Compared with the community sample, patients with stroke with OSA had significantly lower Epworth Sleepiness Scale scores and body mass index for mild OSA (Epworth Sleepiness Scale 9.3+/-0.3 versus 5.6+/-0.5, P<0.001 and body mass index 33.1+/-0.5 versus 28.5+/-1.1, P<0.048) and for moderate to severe OSA (Epworth Sleepiness Scale 9.7+/-0.4 versus 7.1+/-0.9, P=0.043 and body mass index 36.4+/-0.8 versus 27.2+/-0.8 kg/m(2), P<0.025).

Conclusions: For a given severity of OSA, patients with stroke had less daytime sleepiness and lower body mass index than subjects without stroke. These factors may make the diagnosis of OSA elusive in the poststroke period and preclude many such patients from the potential benefits of OSA therapy.

Figure 1

Patients with stroke (solid line) had significantly lower Epworth Sleepiness Scale (ESS) scores in all apnea-hypopnea index (AHI) categories compared to the community sample (dashed line) with no history of stroke indicating less subjective sleepiness (mean±SE: 5.2±0.3 versus 8.4±0.2, 5.6±0.5 versus 9.3±0.3, and 7.1±0.9 versus 9.7±0.4, p-values are adjusted for age, sex and body-mass index). In the community sample, ESS scores increased significantly with increasing AHI category. In contrast, there was no significant difference in ESS scores between stroke patients with an AHI <5 and those with an AHI ≥5 to <15. However, stroke patients with an AHI >15 had a significantly higher ESS score compared to those with an AHI <5.

Figure 2

In the AHI ≥5 to < 15 and AHI ≥15 categories, stroke patients (solid line) had significantly lower body mass index (BMI) than the community sample (dashed line, p-values are adjusted for age and sex). In the community sample, AHI category increased significantly in association with increasing BMI (28.8±0.2, 33.1±0.5 and 36.4±0.8 kg/m², respectively). In contrast, there was no significant increase in AHI category with increasing BMI in stroke patients (27.3±0.8, 28.5±1.1 and 27.2±0.8 kg/m², respectively).

Figure 3

Among stroke patients with obstructive sleep apnea (OSA) (AHI ≥ 5) the percentage who reported excessive daytime sleepiness (ESS score ≥11), and who were obese (BMI ≥30 kg/m²) were significantly lower than among subjects from the community sample with OSA (means [95%CI]: 10 [4 to 22] versus 38 [32 to 44] %, and 26 [16 to 40] versus 71 [65 to 76] %, respectively).