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In total, 2, 514 participants (1, 342 men and 1, 172 women) were enrolled in this study (mean age, 52.37 ± 9.40 years). Among the study population, 122 (4.85%) patients were diagnosed with cognitive impairment, defined as an MMSE score < 24. Table 1 summarizes the characteristics of participants and non-participants. Compared with the group of nonparticipants, the group of study participants was significantly younger; had a higher proportion of women, higher BMI, and a higher prevalence of married family status and high-school graduation; and had a lower reported income, SBP, and fasting blood glucose concentration and a lower proportion of participants with a carotid plaque (Table 1).
Table 1. Comparison of Demographic and other Characteristics of Participants and Non-participants
Variable Overall Participants Non-participants P Value No. 5, 440 2, 514 2, 926 Age (y) 57.7 ± 11.2 55.8 ± 9.5 59.6 ± 12.5 < 0.001 Men, n (%) 3, 257 (59.9) 1, 342 (53.4) 1, 915 (65.4) < 0.001 Marital status (married), n (%) 4, 165 (76. 6) 2, 466 (98.1) 1, 699 (58.1) < 0.001 Body mass index (kg/m) 24.9 ± 3.2 25.0 ± 3.3 24.8 ± 3.2 0.090 Systolic blood pressure (mmHg) 130.9 ± 19.6 128.6 ± 18.6 133.4 ± 20.4 < 0.001 Diastolic blood pressure (mmHg) 82.8 ± 10.9 82.4 ± 10.5 83.1 ± 11.3 0.180 Fasting blood glucose (mmol/L) 5.8 ± 1.9 5.7 ± 1.7 5.8 ± 2.3 < 0.010 Education, n (%) < 0.001 Illiteracy/primary school 1, 104 (21.9) 149 (5.9) 955 (37.6) Middle school 2, 657 (52.6) 1, 544 (61.4) 1, 113 (43.9) High-school graduate 1, 290 (25.5) 821 (32.7) 469 (18.5) Family per-member monthly income ≥ ¥3, 000, n (%) 1, 074 (21.3) 447 (17.8) 627 (24.7) < 0.001 Physical activity > 4 times/week, n (%) 846 (16.8) 311 (12.4) 535 (21.1) < 0.001 Current smoker, n (%) 1, 600 (31.7) 838 (33.3) 762 (30.0) 0.050 Current alcohol drinker, n (%) 1, 444 (28.6) 802 (31.9) 642 (25.3) < 0.001 History of disease Hypertension, n (%) 2, 529 (50.1) 1, 225 (48.7) 1, 304 (51.4) 0.060 Diabetes mellitus, n (%) 703 (13.9) 353 (14.0) 350 (13.8) 0.800 Hyperlipidemia, n (%) 2, 251 (44.6) 1, 281 (50.9) 970 (38.2) < 0.001 Stroke, n (%) 71 (1.3) 24 (1.0) 47 (1.6) < 0.050 Carotid plaque, n (%) 1, 886 (46.6) 1, 053 (42.3) 833 (53.6) < 0.001 Snoring, n (%) 410 (9.6) 273 (10.9) 137 (7.8) < 0.010 Night sleep duration, n (%) ≤ 5 h 684 (12.6) 282 (11.2) 402 (13.7) 6 h 1, 511 (27.8) 675 (26.8) 836 (28.6) 7 h 2, 300 (42.3) 1, 165 (46.3) 1, 135 (38.8) 8 h 881 (16.2) 367 (14.6) 514 (17.6) ≥ 9 h 64 (1.2) 25 (1.0) 39 (1.3) Table 2 presents the characteristics of patients with good cognition and cognitive impairment. Age, sex, marital status, SBP, education, income level, alcohol use, and history of hypertension and carotid plaque were associated with cognitive impairment (P < 0.05). Compared with patients with good cognition, patients with cognitive impairment had a higher proportion of participants with a night sleep duration of ≥ 9 h (4.10% vs. 0.84%, P < 0.001).
Table 2. Comparisons between Patients with and without Cognitive Impairment in the Kailuan Study
Variable Overall Cognitively Intact
(MMSE ≥ 24)Cognitively Impaired
(MMSE < 24)P Value No. 2, 514 2, 392 122 Age (y) 55.8 ± 9.5 55.3 ± 9.1 65.3 ± 11.9 < 0.001 Men, n (%) 1, 342 (53.4) 1, 260 (52.7) 82 (67.2) < 0.001 Marital status (married), n (%) 2, 466 (98.1) 2, 352 (98.3) 114 (93.4) < 0.001 Body mass index (kg/m) 25.0 ± 3.3 25.0 ± 3.3 24.9 ± 3.5 0.850 Systolic blood pressure (mmHg) 128.6 ± 18.6 128.2 ± 18.4 137.4 ± 20.1 < 0.001 Diastolic blood pressure (mmHg) 82.4 ± 10.5 82.4 ± 10.4 84.2 ± 11.1 0.080 Fasting blood glucose (mmol/L) 5.7 ± 1.7 5.7 ± 1.6 6.1 ± 2.4 0.080 Education, n (%) < 0.001 Illiteracy/primary school 149 (5.9) 121 (5.1) 28 (23.0) Middle school 1, 544 (61.4) 1, 458 (61.0) 86 (70.5) High-school graduate 821 (32.7) 813 (33.9) 8 (6.6) Family per-member monthly income ≥ ¥3, 000, n (%) 447 (17.8) 432 (18.1) 15 (12.3) < 0.050 Physical activity > 4 times/week, n (%) 311 (12.4) 299 (12.5) 12 (9.8) 0.120 Current smoker, n (%) 838 (33.3) 790 (33.0) 48 (39.3) 0.240 Current alcohol drinker, n (%) 802 (31.9) 764 (31.9) 38 (31.2) < 0.001 History of disease Hypertension, n (%) 1, 225 (48.7) 1, 145 (47.9) 80 (65.6) < 0.001 Diabetes mellitus, n (%) 353 (14.0) 330 (13.8) 23 (18.9) 0.140 Hyperlipidemia, n (%) 1, 281 (50.9) 1, 227 (51.3) 54 (44.3) 0.130 Stroke, n (%) 24 (1.0) 20 (0.8) 4 (3.3) < 0.050 Carotid plaque, n (%) 1, 053 (42.3) 982 (41.4) 71 (59.2) < 0.001 Snoring, n (%) 273 (10.9) 255 (10.7) 18 (14.8) 0.370 Night sleep duration, n (%) < 0.001 ≤ 5 h 282 (11.2) 255 (10.7) 27 (22.1) 6 h 675 (26.8) 643 (26.9) 32 (26.2) 7 h 1, 165 (46.3) 1, 125 (47.0) 40 (32.8) 8 h 367 (14.6) 349 (14.6) 18 (14.8) ≥ 9 h 25 (1.0) 20 (0.8) 5 (4.1) Note.MMSE: mini-mental state examination. Table 3 shows the baseline characteristics of participants according to mean night sleep duration. The baseline characteristics of the participants varied significantly between sleep categories except marital status (P = 0.22), BMI (P = 0.30), and history of hyperlipidemia (P = 0.11). In particular, most of the short-duration sleepers or long-duration sleepers were older and male participants, and they had a greater likelihood of having hypertension, diabetes mellitus, snoring, and carotid plaque.
Table 3. Characteristics (2012) according to Night Sleep Duration
Variable Night Sleep Duration ≤ 5 h 6 h 7 h 8 h ≥ 9 h P No. 282 675 1, 165 367 25 Age (y) 58.0 ± 10.9 56.3 ± 9.6 55.4 ± 9.0 54.1 ± 8.8 58.1 ± 11.4 < 0.001 Men, n (%) 175 (62.1) 385 (57.0) 593 (50.9) 173 (47.1) 16 (64.0) < 0.001 Marital status (married), n (%) 274 (97.2) 657 (97.3) 1, 149 (98.6) 361 (98.4) 25 (100) 0.220 Body mass index (kg/m2) 25.2 ± 3.4 25.1 ± 3.3 24.8 ± 3.3 25.1 ± 3.2 25.7 ± 3.9 0.300 Systolic blood pressure (mmHg) 130.4 ± 19.6 129.9 ± 18.2 127.7 ± 18.4 127.6 ± 18.8 133.6 ± 18.8 < 0.050 Diastolic blood pressure (mmHg) 82.8 ± 10.8 83.3 ± 10.1 81.9 ± 10.5 82.0 ± 10.5 85.9 ± 11.3 < 0.050 Fasting blood glucose (mmol/L) 5.8 ± 1.7 5.8 ± 1.7 5.6 ± 1.6 5.7 ± 1.7 6.9 ± 3.8 < 0.050 Education, n (%) < 0.001 Illiteracy/primary school 22 (7.8) 39 (5.8) 58 (5.0) 29 (7.9) 1 (4.0) Middle school 194 (68.8) 438 (64.9) 670 (57.5) 221 (60.2) 21 (84.0) High-school graduate 66 (23.4) 198 (29.3) 437 (37.5) 117 (31.9) 3 (12.0) Family per-member monthly income ≥ ¥3, 000, n (%) 40 (14.2) 112 (16.6) 232 (19.9) 60 (16.4) 3 (12.0) < 0.001 Physical activity > 4 times/week, n (%) 52 (18.4) 97 (14.4) 121 (10.4) 38 (10.4) 3 (12.0) < 0.001 Current smoker, n (%) 110 (39.0) 246 (36.4) 370 (31.8) 105 (28.6) 7 (28.0) < 0.050 Current alcohol drinker, n (%) 111 (39.4) 241 (35.7) 343 (29.4) 99 (26.9) 8 (32.0) < 0.050 History of disease Hypertension, n (%) 151 (53.6) 349 (51.7) 553 (47.5) 158 (43.1) 14 (56.0) < 0.050 Diabetes mellitus, n (%) 37 (13.1) 107 (15.8) 148 (12.7) 53 (14.4) 8 (32.0) < 0.050 Hyperlipidemia, n (%) 148 (52.5) 372 (55.1) 569 (48.8) 180 (49.1) 12 (48.0) 0.110 Stroke, n (%) 2 (0.7) 12 (1.8) 8 (0.7) 1 (0.3) 1 (4.0) < 0.050 Carotid plaque, n (%) 154 (55.0) 292 (43.9) 461 (39.8) 135 (37.1) 11 (44.0) < 0.001 Snoring, n (%) 64 (22.7) 86 (12.7) 88 (7.6) 32 (8.7) 3 (12.0) < 0.001 A multivariate regression analysis was performed to investigate the association between night sleep duration and cognitive function (Table 4). After adjusting for age, sex, family per-member monthly income, education level, marital status, smoking status, drinking status, physical activity, BMI, history of diabetes, hypertension, hyperlipidemia, stroke, and carotid plaque, compared with the participants sleeping 7 h, the multivariable adjusted odds ratios (in model 3) of cognitive impairment among participants were 2.14 (95% CI, 1.20-3.83) for ≤ 5 h, 1.13 (95% CI, 0.67-1.89) for 6 h, 1.51 (95% CI, 0.82-2.79) for 8 h, and 5.37 (95% CI, 1.62-17.80) for ≥ 9 h sleep duration.
Table 4. Odds Ratios (95% CI) for Cognitive Impairment according to Night Sleep Duration
Items 95% CI (according to Night Sleep Duration) ≤ 5 h 6 h 7 h 8 h ≥ 9 h Cases, n (%) 27 (9.57) 32 (4.74) 40 (3.43) 18 (4.90) 5 (20.00) Model 1† 2.27 (1.34-3.86) 1.26 (0.78-2.06) Reference 1.65 (0.92-2.96) 5.54 (1.78-17.28) Model 2‡ 2.12 (1.20-3.77) 1.18 (0.71-1.95) Reference 1.46 (0.79-2.68) 5.86 (1.83-18.72) Model 3§ 2.14 (1.20-3.83) 1.13 (0.67-1.89) Reference 1.51 (0.82-2.79) 5.37 (1.62-17.80) Note.CI, confidence interval; †Model 1 was adjusted for age and sex; ‡Model 2 was adjusted for age, sex, family per-member monthly income, education level, marital status, smoking status, drinking status, physical activity, and body mass index; §Model 3 was adjusted for the variables in model 2 plus history of diabetes, hypertension, hyperlipidemia, stroke, and carotid plaque. We also analyzed the interactions between night sleep duration and sex/age for cognitive impairment and no significant interactions were observed (P= 0.32/0.95).
doi: 10.3967/bes2017.100
Night Sleep Duration and Risk of Cognitive Impairment in a Chinese Population:A Cross-sectional Study
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Abstract:
Objective Although sleep is one of the most important health-related behavioral factors, the association between night sleep duration and cognitive impairment has not been fully understood. A cross-sectional study was conducted with a random sample of 2, 514 participants (≥ 40 years of age; 46.6% women) in China to examine the association between night sleep duration and cognitive impairment. Methods Night sleep duration was categorized as ≤ 5, 6, 7, 8, or ≥ 9 h per night. Cognitive function was measured using the Mini-Mental State Examination. A multivariate regression analysis was used to analyze the association of night sleep duration with cognitive impairment. A total of 122 participants were diagnosed with cognitive impairment. Results A U-shaped association between night sleep duration and cognitive impairment was found. The odds ratios (95% confidence intervals) of cognitive impairment (with 7 h of daily sleep being considered as the reference) for individuals reporting ≤ 5, 6, 8, and ≥ 9 h were 2.14 (1.20-3.83), 1.13 (0.67-1.89), 1.51 (0.82-2.79), and 5.37 (1.62-17.80), respectively (P ≤ 0.01). Conclusion Short or long night sleep duration was an important sleep-related factor independently associated with cognitive impairment and may be a useful marker for increased risk of cognitive impairment. -
Key words:
- Night sleep duration /
- Cognitive /
- Impairment /
- Cross-sectional
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Table 1. Comparison of Demographic and other Characteristics of Participants and Non-participants
Variable Overall Participants Non-participants P Value No. 5, 440 2, 514 2, 926 Age (y) 57.7 ± 11.2 55.8 ± 9.5 59.6 ± 12.5 < 0.001 Men, n (%) 3, 257 (59.9) 1, 342 (53.4) 1, 915 (65.4) < 0.001 Marital status (married), n (%) 4, 165 (76. 6) 2, 466 (98.1) 1, 699 (58.1) < 0.001 Body mass index (kg/m) 24.9 ± 3.2 25.0 ± 3.3 24.8 ± 3.2 0.090 Systolic blood pressure (mmHg) 130.9 ± 19.6 128.6 ± 18.6 133.4 ± 20.4 < 0.001 Diastolic blood pressure (mmHg) 82.8 ± 10.9 82.4 ± 10.5 83.1 ± 11.3 0.180 Fasting blood glucose (mmol/L) 5.8 ± 1.9 5.7 ± 1.7 5.8 ± 2.3 < 0.010 Education, n (%) < 0.001 Illiteracy/primary school 1, 104 (21.9) 149 (5.9) 955 (37.6) Middle school 2, 657 (52.6) 1, 544 (61.4) 1, 113 (43.9) High-school graduate 1, 290 (25.5) 821 (32.7) 469 (18.5) Family per-member monthly income ≥ ¥3, 000, n (%) 1, 074 (21.3) 447 (17.8) 627 (24.7) < 0.001 Physical activity > 4 times/week, n (%) 846 (16.8) 311 (12.4) 535 (21.1) < 0.001 Current smoker, n (%) 1, 600 (31.7) 838 (33.3) 762 (30.0) 0.050 Current alcohol drinker, n (%) 1, 444 (28.6) 802 (31.9) 642 (25.3) < 0.001 History of disease Hypertension, n (%) 2, 529 (50.1) 1, 225 (48.7) 1, 304 (51.4) 0.060 Diabetes mellitus, n (%) 703 (13.9) 353 (14.0) 350 (13.8) 0.800 Hyperlipidemia, n (%) 2, 251 (44.6) 1, 281 (50.9) 970 (38.2) < 0.001 Stroke, n (%) 71 (1.3) 24 (1.0) 47 (1.6) < 0.050 Carotid plaque, n (%) 1, 886 (46.6) 1, 053 (42.3) 833 (53.6) < 0.001 Snoring, n (%) 410 (9.6) 273 (10.9) 137 (7.8) < 0.010 Night sleep duration, n (%) ≤ 5 h 684 (12.6) 282 (11.2) 402 (13.7) 6 h 1, 511 (27.8) 675 (26.8) 836 (28.6) 7 h 2, 300 (42.3) 1, 165 (46.3) 1, 135 (38.8) 8 h 881 (16.2) 367 (14.6) 514 (17.6) ≥ 9 h 64 (1.2) 25 (1.0) 39 (1.3) Table 2. Comparisons between Patients with and without Cognitive Impairment in the Kailuan Study
Variable Overall Cognitively Intact
(MMSE ≥ 24)Cognitively Impaired
(MMSE < 24)P Value No. 2, 514 2, 392 122 Age (y) 55.8 ± 9.5 55.3 ± 9.1 65.3 ± 11.9 < 0.001 Men, n (%) 1, 342 (53.4) 1, 260 (52.7) 82 (67.2) < 0.001 Marital status (married), n (%) 2, 466 (98.1) 2, 352 (98.3) 114 (93.4) < 0.001 Body mass index (kg/m) 25.0 ± 3.3 25.0 ± 3.3 24.9 ± 3.5 0.850 Systolic blood pressure (mmHg) 128.6 ± 18.6 128.2 ± 18.4 137.4 ± 20.1 < 0.001 Diastolic blood pressure (mmHg) 82.4 ± 10.5 82.4 ± 10.4 84.2 ± 11.1 0.080 Fasting blood glucose (mmol/L) 5.7 ± 1.7 5.7 ± 1.6 6.1 ± 2.4 0.080 Education, n (%) < 0.001 Illiteracy/primary school 149 (5.9) 121 (5.1) 28 (23.0) Middle school 1, 544 (61.4) 1, 458 (61.0) 86 (70.5) High-school graduate 821 (32.7) 813 (33.9) 8 (6.6) Family per-member monthly income ≥ ¥3, 000, n (%) 447 (17.8) 432 (18.1) 15 (12.3) < 0.050 Physical activity > 4 times/week, n (%) 311 (12.4) 299 (12.5) 12 (9.8) 0.120 Current smoker, n (%) 838 (33.3) 790 (33.0) 48 (39.3) 0.240 Current alcohol drinker, n (%) 802 (31.9) 764 (31.9) 38 (31.2) < 0.001 History of disease Hypertension, n (%) 1, 225 (48.7) 1, 145 (47.9) 80 (65.6) < 0.001 Diabetes mellitus, n (%) 353 (14.0) 330 (13.8) 23 (18.9) 0.140 Hyperlipidemia, n (%) 1, 281 (50.9) 1, 227 (51.3) 54 (44.3) 0.130 Stroke, n (%) 24 (1.0) 20 (0.8) 4 (3.3) < 0.050 Carotid plaque, n (%) 1, 053 (42.3) 982 (41.4) 71 (59.2) < 0.001 Snoring, n (%) 273 (10.9) 255 (10.7) 18 (14.8) 0.370 Night sleep duration, n (%) < 0.001 ≤ 5 h 282 (11.2) 255 (10.7) 27 (22.1) 6 h 675 (26.8) 643 (26.9) 32 (26.2) 7 h 1, 165 (46.3) 1, 125 (47.0) 40 (32.8) 8 h 367 (14.6) 349 (14.6) 18 (14.8) ≥ 9 h 25 (1.0) 20 (0.8) 5 (4.1) Note.MMSE: mini-mental state examination. Table 3. Characteristics (2012) according to Night Sleep Duration
Variable Night Sleep Duration ≤ 5 h 6 h 7 h 8 h ≥ 9 h P No. 282 675 1, 165 367 25 Age (y) 58.0 ± 10.9 56.3 ± 9.6 55.4 ± 9.0 54.1 ± 8.8 58.1 ± 11.4 < 0.001 Men, n (%) 175 (62.1) 385 (57.0) 593 (50.9) 173 (47.1) 16 (64.0) < 0.001 Marital status (married), n (%) 274 (97.2) 657 (97.3) 1, 149 (98.6) 361 (98.4) 25 (100) 0.220 Body mass index (kg/m2) 25.2 ± 3.4 25.1 ± 3.3 24.8 ± 3.3 25.1 ± 3.2 25.7 ± 3.9 0.300 Systolic blood pressure (mmHg) 130.4 ± 19.6 129.9 ± 18.2 127.7 ± 18.4 127.6 ± 18.8 133.6 ± 18.8 < 0.050 Diastolic blood pressure (mmHg) 82.8 ± 10.8 83.3 ± 10.1 81.9 ± 10.5 82.0 ± 10.5 85.9 ± 11.3 < 0.050 Fasting blood glucose (mmol/L) 5.8 ± 1.7 5.8 ± 1.7 5.6 ± 1.6 5.7 ± 1.7 6.9 ± 3.8 < 0.050 Education, n (%) < 0.001 Illiteracy/primary school 22 (7.8) 39 (5.8) 58 (5.0) 29 (7.9) 1 (4.0) Middle school 194 (68.8) 438 (64.9) 670 (57.5) 221 (60.2) 21 (84.0) High-school graduate 66 (23.4) 198 (29.3) 437 (37.5) 117 (31.9) 3 (12.0) Family per-member monthly income ≥ ¥3, 000, n (%) 40 (14.2) 112 (16.6) 232 (19.9) 60 (16.4) 3 (12.0) < 0.001 Physical activity > 4 times/week, n (%) 52 (18.4) 97 (14.4) 121 (10.4) 38 (10.4) 3 (12.0) < 0.001 Current smoker, n (%) 110 (39.0) 246 (36.4) 370 (31.8) 105 (28.6) 7 (28.0) < 0.050 Current alcohol drinker, n (%) 111 (39.4) 241 (35.7) 343 (29.4) 99 (26.9) 8 (32.0) < 0.050 History of disease Hypertension, n (%) 151 (53.6) 349 (51.7) 553 (47.5) 158 (43.1) 14 (56.0) < 0.050 Diabetes mellitus, n (%) 37 (13.1) 107 (15.8) 148 (12.7) 53 (14.4) 8 (32.0) < 0.050 Hyperlipidemia, n (%) 148 (52.5) 372 (55.1) 569 (48.8) 180 (49.1) 12 (48.0) 0.110 Stroke, n (%) 2 (0.7) 12 (1.8) 8 (0.7) 1 (0.3) 1 (4.0) < 0.050 Carotid plaque, n (%) 154 (55.0) 292 (43.9) 461 (39.8) 135 (37.1) 11 (44.0) < 0.001 Snoring, n (%) 64 (22.7) 86 (12.7) 88 (7.6) 32 (8.7) 3 (12.0) < 0.001 Table 4. Odds Ratios (95% CI) for Cognitive Impairment according to Night Sleep Duration
Items 95% CI (according to Night Sleep Duration) ≤ 5 h 6 h 7 h 8 h ≥ 9 h Cases, n (%) 27 (9.57) 32 (4.74) 40 (3.43) 18 (4.90) 5 (20.00) Model 1† 2.27 (1.34-3.86) 1.26 (0.78-2.06) Reference 1.65 (0.92-2.96) 5.54 (1.78-17.28) Model 2‡ 2.12 (1.20-3.77) 1.18 (0.71-1.95) Reference 1.46 (0.79-2.68) 5.86 (1.83-18.72) Model 3§ 2.14 (1.20-3.83) 1.13 (0.67-1.89) Reference 1.51 (0.82-2.79) 5.37 (1.62-17.80) Note.CI, confidence interval; †Model 1 was adjusted for age and sex; ‡Model 2 was adjusted for age, sex, family per-member monthly income, education level, marital status, smoking status, drinking status, physical activity, and body mass index; §Model 3 was adjusted for the variables in model 2 plus history of diabetes, hypertension, hyperlipidemia, stroke, and carotid plaque. -
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