Objectively Measured Sleep Characteristics and Incidence of Ischemic Stroke: The Sleep Heart Health Study

Figures & data

Figure 1 Inclusion and exclusion criteria for the study population. This figure depicts the inclusion of patients into the current investigation as a flowchart. The arrows that branch off represent patients that did not meet the criteria and were excluded.

Table 1 Descriptive Characteristics by WASO Quartile (Quartile I: <30.0min; Quartile II: 30.0min–48.5min; Quartile III:49.0min-80.0min; Quartile IV: >80.0min)

Characteristics	Total (n=4204)	WASO (Min)
		First Quartile (n=1048)	Second Quartile (n=1063)	Third Quartile (n=1047)	Fourth Quartile (n=1046)	P value
Age, year	63.8±11.1	59.2±11.0	61.7±10.6	65.5±10.3	68.7±10.2	<0.001
Gender, n (%)						<0.001
Male	1978 (47.1)	405 (38.6)	470 (44.2)	537 (51.3)	566 (54.1)	–
Female	2226 (52.9)	643 (61.4)	593 (55.8)	510 (48.7)	480 (45.9)	–
Body mass index, kg/m^2	28.2±5.0	28.2±5.2	28.0±4.9	28.4±4.8	28.4±5.0	0.122
Race, n (%)						0.076
White	3668 (87.3)	907 (86.5)	919 (86.5)	938 (89.6)	904 (86.4)	–
Other	536 (12.7)	141 (13.5)	144 (13.5)	109 (10.4)	142 (13.6)	–
Smoking status, n (%)						0.044
Smoker	2260 (53.8)	546 (52.1)	549 (51.7)	568 (54.3)	597 (57.2)	–
Never smoker	1938 (46.2)	502 (47.9)	512 (48.3)	478 (45.7)	446 (42.8)	–
Alcohol use, n (%)						0.170
At least 1 drink per day	1708 (43.3)	419 (42.9)	457 (45.9)	399 (41.0)	433 (43.3)	–
None	2238 (56.7)	557 (57.1)	538 (54.1)	575 (59.0)	568 (56.7)	–
Benzodiazepine use, n (%)	246 (5.9)	48 (4.6)	65 (6.1)	59 (5.6)	74 (7.1)	0.105
Diabetes mellitus, n (%)	295 (7.0)	55 (5.2)	53 (5.0)	93 (8.9)	94 (9.0)	<0.001
Hypertension, n (%)	1681 (40.0)	309 (29.5)	382 (35.9)	447 (42.7)	543 (51.9)	<0.001
AHI, events/h	9.9±13.0	7.8±11.2	8.9±12.2	10.3±12.5	12.5±15.4	<0.001
Sleep duration, h	7.3±0.9	7.0±1.0	7.2±0.9	7.4±0.9	7.7±0.8	<0.001
SE, %	83.4±10.0	91.6±5.5	88.0±4.5	82.7±4.9	71.1±9.5	<0.001
REM, %	19.7±6.8	21.3±6.6	20.3±6.3	19.3±6.7	17.8±7.1	<0.001
SWS, %	17.5±11.9	19.9±12.1	18.3±11.4	15.9±11.5	16.0±12.2	<0.001
SL, min	12.8±19.5	14.0±21.5	12.4±18.6	12.7±18.5	12.2±19.2	0.177
Total ArI, events/h	19.0±10.4	15.4±8.6	18.0±8.8	20.1±10.0	22.7±12.3	<0.001
ArI-REM, events/h	15.2±10.8	13.7±10.0	15.0±10.6	15.3±10.2	16.7±12.3	<0.001
ArI-NREM, events/h	19.9±11.3	15.8±9.3	18.7±9.5	21.2±11.2	24.0±13.3	<0.001
SFI, events/h	8.9±3.4	7.4±2.6	8.5±2.8	9.0±3.0	10.5±4.2	<0.001
Follow-up time, year	10.7±3.0	11.2±2.7	11.0±2.8	10.7±2.9	10.0±3.4	<0.001

Notes: Results are presented as mean ± standard deviation or n (%). The P values represent the difference among four groups.

Abbreviations: AHI, apnea hypopnea index; ArI, arousal index; NREM, non-rapid eye movement; REM, rapid eye movement; SFI, sleep fragmentation index; SL, sleep latency; SWS, slow wave sleep; WASO, wake after sleep onset.

Table 2 HRs and 95% CIs for Sleep Characteristics Associated with Ischemic Stroke

	Univariable Models		Multivariable Adjusted^†		Multivariable Adjusted^‡
Sleep Variables	HR (95% CI)	P	HR (95% CI)	P	HR (95% CI)	P
WASO	1.008 (1.005–1.011)	<0.001	1.003 (1.000–1.007)	0.049	1.004 (1.000–1.008)	0.028
SE	0.964 (0.951–0.977)	<0.001	0.980 (0.966–0.995)	0.011	0.981 (0.966–0.996)	0.012
REM, %	0.971 (0.947–0.995)	0.017	0.993 (0.969–1.019)	0.598	0.994 (0.970–1.020)	0.665
SWS, %	0.993 (0.978–1.008)	0.361	0.992 (0.977–1.008)	0.346	0.992 (0.976–1.007)	0.300
SL	1.003 (0.994–1.011)	0.551	1.002 (0.993–1.011)	0.639	1.002 (0.993–1.010)	0.693
SFI	1.036 (0.987–1.087)	0.149	1.007 (0.959–1.057)	0.780	1.006 (0.958–1.056)	0.815
Total ArI	1.002 (0.985–1.019)	0.798	0.992 (0.972–1.013)	0.462	0.992 (0.972–1.013)	0.450
ArI-REM	0.986 (0.968–1.004)	0.128	0.986 (0.967–1.005)	0.149	0.987 (0.968–1.005)	0.162
ArI-NREM	1.005 (0.990–1.020)	0.539	0.995 (0.978–1.014)	0.623	0.995 (0.977–1.013)	0.607
Sleep duration
<6h	1.943 (1.173–3.220)	0.010	1.725 (1.026–2.899)	0.040
>8h	1.326 (0.893–1.970)	0.162	1.223 (0.816–1.833)	0.330
6h–8h	1(Ref)		1(Ref)

Notes: ^†Each individual sleep characteristics was adjusted by age, gender, smoking status, race, body mass index, prevalent hypertension and diabetes mellitus, apnea-hypopnea index, benzodiazepine use, alcohol use. ^‡Adjusted by ^†plus sleep duration.

Abbreviations: ArI, arousal index; 95% CI, 95% confidence interval; HR, hazard ratio; NREM, non-rapid eye movement; REM, rapid eye movement; SFI, sleep fragmentation index; SL, sleep latency; SWS, slow wave sleep.

Table 3 HRs and 95% CIs for Quartiles of WASO and SE Associated with Ischemic Stroke

	Univariable Models		Multivariable Adjusted^†		Multivariable Adjusted^‡
All Subjects	HR (95% CI)	P	HR (95% CI)	P	HR (95% CI)	P
WASO
Fourth quartile (>80 min)	4.996 (2.600–9.597)	<0.001	3.298 (1.608–6.768)	0.001	3.771 (1.805–7.877)	<0.001
Third quartile (49.0min–80min)	3.299 (1.675–6.496)	0.001	2.749 (1.317–5.738)	0.007	3.009 (1.433–6.317)	0.004
Second quartile (30.0min–48.5min)	3.005 (1.519–5.945)	0.002	2.933 (1.392–6.183)	0.005	3.108 (1.470–6.568)	0.003
First quartile (<30.0 min)	1(Ref)		1(Ref)		1(Ref)
Sleep efficiency
First quartile (<80.0%)	3.726 (2.174–6.386)	<0.001	2.210 (1.241–3.936)	0.007	2.220 (1.244–3.960)	0.007
Second quartile (80.0–84.9%)	2.467 (1.332–4.569)	0.004	1.859 (0.970–3.564)	0.062	1.829 (0.952–3.514)	0.070
Third quartile (85.0–89.9%)	1.866 (1.017–3.423)	0.044	1.443 (0.762–2.732)	0.261	1.457 (0.769–2.760)	0.248
Fourth quartile (≥90%)	1(Ref)		1(Ref)		1(Ref)

Notes: ^†Adjusted by age, gender, smoking status, race, body mass index, prevalent hypertension and diabetes mellitus, apnea-hypopnea index, benzodiazepine use, alcohol use. ^‡Adjusted by ^†plus sleep duration.

Abbreviations: 95% CI, 95% confidence interval; HR, hazard ratio; WASO, wake after sleep onset.

Figure 2 Kaplan-Meier plots of cumulative risk for ischemic stroke stratified by WASO quartiles ((A); quartile I <30.0 min; quartile II: 30.0 min-48.5 min; quartile III: 49.0 min-80.0 min; quartile IV: >80.0 min) and SE ((B); quartile I <80%, quartile II: 80%-84.9%, quartile III: 85%-89.9%, and quartile IV: ≥90%).