Table 2.
Baseline characteristics stratified by nocturnal sleep duration: the Heinz Nixdorf Recall Study.
| Variable | Time asleep | |||||
|---|---|---|---|---|---|---|
| ≤ 5 h | > 5 h to < 7 h | 7 h to < 8 h | 8 h to < 9 h | ≥ 9 h | ||
| N | 209 (100.0%) | 612 (100.0%) | 655 (100.0%) | 352 (100.0%) | 62 (100.0%) | |
| Sex | Female | 138 (66.0%) | 311 (50.8%) | 336 (51.3%) | 162 (46.0%) | 26 (41.9%) |
| Age (years) | 57.5 ± 7.2 | 56.7 ± 7.0 | 57.9 ± 7.0 | 60.2 ± 7.1 | 60.8 ± 6.1 | |
| Sleep Quality: PSQI Scorea | 11.0 ± 3.4 | 6.6 ± 2.9 | 4.0 ± 2.1 | 3.4 ± 1.9 | 3.2 ± 1.9 | |
| > 5 | 197 (94.3%) | 369 (60.3%) | 134 (20.5%) | 40 (11.4%) | 7 (11.3%) | |
| Difficulties Initiating Sleep | Sometimes | 45 (21.5%) | 231 (37.7%) | 262 (40.0%) | 130 (36.9%) | 21 (33.9%) |
| Often | 64 (30.6%) | 125 (20.4%) | 93 (14.2%) | 28 (8.0%) | 6 (9.7%) | |
| Almost every Night | 66 (31.6%) | 43 (7.0%) | 19 (2.9%) | 8 (2.3%) | 2 (3.2%) | |
| Difficulties Maintaining Sleep | Sometimes | 19 (9.1%) | 142 (23.2%) | 177 (27.0%) | 114 (32.4%) | 14 (22.6%) |
| Often | 60 (28.7%) | 164 (26.8%) | 180 (27.5%) | 92 (26.1%) | 12 (19.4%) | |
| Almost every Night | 124 (59.3%) | 255 (41.7%) | 209 (31.9%) | 104 (29.5%) | 29 (46.8%) | |
| Early-morning Awakening | Sometimes | 45 (21.5%) | 187 (30.6%) | 227 (34.7%) | 117 (33.2%) | 19 (30.6%) |
| Often | 62 (29.7%) | 144 (23.5%) | 98 (15.0%) | 44 (12.5%) | 1 (1.6%) | |
| Almost every Night | 62 (29.7%) | 76 (12.4%) | 25 (3.8%) | 10 (2.8%) | 3 (4.8%) | |
| APOE ε4 Genotype | ε4 Carrierb | 42 (20.1%) | 152 (24.8%) | 173 (26.4%) | 85 (24.1%) | 15 (24.2%) |
| Alcohol Consumption [g/week] | 9.77 ± 17.39 | 9.8 ± 17.4 | 8.1 ± 13.8 | 8.9 ± 15.4 | 9.4 ± 16.2 | |
| Depression Scorec | 9.1 ± 5.9 | 7.7 ± 5.9 | 6.7 ± 5.4 | 6.6 ± 5.4 | 6.5 ± 6.2 | |
| Framingham Risk Score | 0.2 ± 0.2 | 0.2 ± 0.2 | 0.2 ± 0.2 | 0.3 ± 0.2 | 0.3 ± 0.2 | |
| Height [cm] | 167.1 ± 9.4 | 169.4 ± 9.0 | 169.5 ± 9.3 | 169.5 ± 9.1 | 170.9 ± 9.0 | |
| ISCED [years] | 13.9 ± 2.1 | 14.5 ± 2.4 | 14.5 ± 2.4 | 14.3 ± 2.3 | 13.8 ± 2.1 | |
| Physical Activity [MET-h/Week] | 40.64 ± 44.81 | 40.6 ± 44.8 | 42.1 ± 39.3 | 45.6 ± 42.2 | 52.4 ± 55.2 | |
| Waist Circumference [cm] | 92.3 ± 14.6 | 91.9 ± 12.8 | 92.4 ± 12.4 | 93.4 ± 12.3 | 95.7 ± 14.3 | |
| Smoking Status | Former Smoker | 75 (35.9%) | 240 (39.2%) | 239 (36.5%) | 128 (36.4%) | 23 (37.1%) |
| Current Smoker | 42 (20.1%) | 126 (20.6%) | 110 (16.8%) | 83 (23.6%) | 13 (21.0%) | |
All numbers were derived from the complete case analysis dataset (N = 1890). Data is displayed as N (Col Percent) or Mean ± Standard Deviation. Reference Categories were omitted. Abbreviations: PSQI: Pittsburgh Sleep Quality Index; g: Gramm; cm: Centimetres; ISCED: International Standard Classification of Education; MET-h: Metabolic Equivalent of Task – hours, APOE. Apolipoprotein E.
aScore > 5 indicates poor sleep quality bɛ4 carrier: at least one 4 allele (ɛ2/ɛ4, ɛ3/ɛ4, ɛ4/ɛ4) cCentre for Epidemiologic Studies Depression Scale, higher scores indicate higher levels of depression.