Table 4.
Adjusted relative risks for the association between subjective sleep duration and the incidence of mild cognitive impairment at t2: the Heinz Nixdorf Recall Study.
| Exposure | Complete Case Analysis (N = 1890) | Multiple Imputation (N = 2480) | ||||||
|---|---|---|---|---|---|---|---|---|
| N | n (%) | RR | 95% CI | n % | RR | 95% CI | ||
| Time in bed during the nighta | ≤ 5 h | 13 | 3 (23.1%) | 3.14 | [1.16 to 8.49] | 22.8% | 2.86 | [1.24 to 6.60] |
| > 5 h to <7 h | 209 | 13 (6.2%) | 0.82 | [0.45 to 1.50] | 8.1% | 0.96 | [0.56 to 1.64] | |
| 7 h to <8 h | 472 | 40 (8.5%) | 1.00 | Reference | 9.0% | 1.00 | Reference | |
| 8 h to <9 h | 655 | 70 (10.7%) | 1.09 | [0.75 to 1.59] | 10.7% | 1.08 | [0.77 to 1.52] | |
| ≥ 9 h | 535 | 75 (14.0%) | 1.33 | [0.92 to 1.94] | 13.4% | 1.30 | [0.93 to 1.82] | |
| Time asleepb | ≤ 5 h | 209 | 28 (13.4%) | 1.28 | [0.86 to 1.90] | 13.5% | 1.19 | [0.83 to 1.72] |
| > 5 h to <7 h | 612 | 58 (9.5%) | 0.91 | [0.65 to 1.26] | 10.0% | 0.91 | [0.69 to 1.22] | |
| 7 h to <8 h | 655 | 71 (10.8%) | 1.00 | Reference | 11.2% | 1.00 | Reference | |
| 8 h to <9 h | 352 | 39 (11.1%) | 0.90 | [0.62 to 1.30] | 10.7% | 0.88 | [0.63 to 1.24] | |
| ≥ 9 h | 62 | 5 (8.1%) | 0.66 | [0.28 to 1.59] | 8.5% | 0.70 | [0.32 to 1.54] | |
| Total Sleep Durationa,c | ≤ 5 h | 7 | 2 (28.6%) | 2.01 | [1.27 to 3.19] | 21.8% | 2.63 | [0.70 to 9.85] |
| > 5 h to <7 h | 198 | 13 (6.6%) | 1.09 | [0.75 to 1.58] | 8.9% | 1.11 | [0.65 to 1.92] | |
| 7 h to <8 h | 447 | 33 (7.4%) | 1.00 | Reference | 8.4% | 1.00 | Reference | |
| 8 h to <9 h | 627 | 71 (11.3%) | 1.35 | [0.95 to 1.92] | 11.1% | 1.19 | [0.83 to 1.70] | |
| ≥ 9 h | 605 | 82 (13.6%) | 1.65 | [1.01 to 2.68] | 13.0% | 1.31 | [0.92 to 1.85] | |
Estimates of relative risks with 95% confidence intervals were obtained from a log-linear model with a Poisson working likelihood and robust standard errors.
Abbreviations: t1: second visit in the Heinz Nixdorf Recall Study (HNR Study); t2: third visit in the HNR Study; RR: relative risk; n %: percent of cases; CI: Confidence Interval
Model is adjusted for age (cont.) and sex (male/female), height (cont.), waist (cont.), Framingham CVD risk score (cont.), smoking status (never/former/current), ISC education years (cont.), physical activity (cont.; MET-h/week), pure alcohol consumption (cont.; g/week), APOE e4 genotype (carrier/non-carrier), and depression score (cont.).
aComplete Case N = 1884, because of 6 additional missing data for time in bed.
bTime asleep does not include time awake in bed.
cTotal sleep duration includes time in bed during the night plus daytime napping.