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. Author manuscript; available in PMC: 2017 Mar 1.
Published in final edited form as: Am J Geriatr Psychiatry. 2016 Jan 29;24(3):248–258. doi: 10.1016/j.jagp.2015.12.002

Table 1.

Baseline Characteristics of Participants for Overall Cohort by Averaged Sleep Efficiency

Quartilea of Averaged Sleep Efficiency, %
Characteristic Overall (N=1245) Q1 (N=311) Q2 (N=311) Q3 (N=311) Q4 (N=312) P-valueb χ2 [d.f, N] or F-value [d.f]
Age, years, mean (SD) 82.63 (3.32) 82.2 (3.70) 82.63 (3.36) 82.91 (3.27) 82.77 (2.85) 0.04 F = 2.73 [3, 1241]
Caucasian, n (%) 1109 (89.08) 243 (78.14) 276 (88.75) 292 (93.89) 298 (95.51) <0.001 χ2 = 58.99 [3, 1245]
Self-reported health status, n (%) <0.001 χ2 = 23.76 [6, 1245]
    Poor/very poor 16 (1.29) 7 (2.25) 6 (1.93) 1 (0.32) 2 (0.64)
    Fair 225 (18.07) 72 (23.15) 67 (21.54) 40 (12.86) 46 (14.74)
    Good/excellent 1004 (80.64) 232 (74.60) 238 (76.53) 270 (86.82) 264 (84.62)
Education, years, mean (SD) 12.88 (2.57) 12.73 (2.54) 12.9 (2.54) 12.86 (2.66) 13.03 (2.53) 0.54 F = 0.71 [3, 1241]
Lives alone, n (%) 734 (58.96) 181 (58.20) 184 (59.16) 180 (57.88) 189 (60.58) 0.90 χ2 = 0.57 [3, 1245]
Average drinks per week, mean (SD) 1.12 (2.87) 1.29 (3.67) 1.02 (2.48) 1.03 (2.35) 1.16 (2.79) 0.70 χ2 = 1.42 [3, 1245]
Never smoked, n (%) 824 (66.18) 193 (62.06) 200 (64.31) 207 (66.56) 224 (71.79) 0.21 χ2 = 8.46 [6, 1245]
Current antidepressant use, n (%) 131 (10.52) 42 (13.50) 29 (9.32) 28 (9.00) 32 (10.26) 0.24 χ2 = 4.20 [3, 1245]
Current benzodiazepine use, n (%) 84 (6.75) 27 (8.68) 19 (6.11) 20 (6.43) 18 (5.77) 0.46 χ2 = 2.57 [3, 1245]
Current prescription sleep medication use, n (%) 14 (1.12) 7 (2.25) 2 (0.64) 3 (0.96) 2 (0.64) 0.18 χ2 = 4.92 [3, 1245]
# of medical conditionsc (0-8), mean (SD) 1.39 (1.11) 1.59 (1.16) 1.41 (1.08) 1.31 (1.12) 1.25 (1.04) <0.001 χ2 = 16.78 [3, 1244]
GDS score (0-15), mean (SD) 1.9 (2.21) 2.34 (2.45) 1.93 (2.29) 1.62 (1.92) 1.73 (2.10) <0.001 χ2 = 21.21 [3, 1243]
IADL impairments (0 - 6), mean (SD) 1.12 (1.57) 1.51 (1.76) 1.11 (1.52) 1.11 (1.59) 0.76 (1.27) <0.001 χ2 = 32.33 [3, 1245]
BMI, kg/m2, mean (SD) 27.5 (4.82) 28.92 (5.26) 27.67 (5.01) 26.89 (4.47) 26.53 (4.14) <0.001 F = 15.40 [3, 1235]
Walks for exercise, n (%) 516 (41.88) 119 (38.89) 129 (41.75) 142 (45.95) 126 (40.91) 0.34 χ2 = 3.35 [3, 1232]
MMSE (0-30), mean (SD) 28.49 (1.36) 28.24 (1.43) 28.48 (1.35) 28.62 (1.36) 28.61 (1.27) 0.001 χ2 = 15.97 [3, 1245]
Visit 9 3MS (0-100), mean (SD) 88.10 (9.67) 86.58 (9.83) 88.46 (9.82) 87.81 (10.75) 89.56 (7.86) <0.001 χ2 = 19.81 [3, 1244]
Visit 9 cognitive status, n (%) 0.03 χ2 = 14.04 [6, 1245]
    Normal 772 (62.01) 177 (56.91) 193 (62.06) 190 (61.09) 212 (67.95)
    MCI 290 (23.29) 83 (26.69) 63 (20.26) 74 (23.79) 70 (22.44)
    Dementia 183 (14.70) 51 (16.40) 55 (17.68) 47 (15.11) 30 (9.62)

Abbreviations: GDS, Geriatric Depression Scale; IADL, instrumental activities of daily living; BMI, body mass index; MMSE, Mini-Mental State Examination; 3MS, Modified Mini-Mental State Examination; MCI, Mild Cognitive Impairment

a

Quartile cutpoints: 74.39, 81.84, 86.26

b

p-values for continuous variables are from ANOVA (F-statistic) for normally distributed variables, a Kruskall-Wallis test (χ2) for skewed data; p-values for categorical are data from a chi-square test for homogeneity (χ2).

c

Select medical conditions include history of cancer, stroke, diabetes, Parkinson's disease, chronic obstructive pulmonary disease, congestive heart failure, hypertension and coronary heart disease (angina/myocardial infarction)

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