Table 1.
Descriptive statistics for study participants with and without sleep problems by cohort
Score/value | Non-demented elderly
|
Poss/prob AD
|
||
---|---|---|---|---|
SP+ (N = 325) | SP− (N = 74) | SP+ (N = 73) | SP− (N = 190) | |
Age (years) | 83.6 ± 7.3††† | 81.5 ± 8.7 | 74.8 ± 12.6 | 73.7 ± 11.5 |
Sex (% female)‡ | 68.9 | 58.8 | 53.4 | 54.2 |
Education (years) | 13.2 ± 2.7†† | 14.1 ± 2.7*** | 14.2 ± 3.3 | 13.4 ± 3.3* |
Duration of AD (years) | 5.2 ± 3.0 | 4.4 ± 2.8* | ||
Mini-mental state exam (MMSE) | 28.1 ± 1.5††† | 28.2 ± 1.5 | 18.7 ± 7.2 | 19.4 ± 6.0 |
ADL | 0.3 ± 0.7††† | 0.2 ± 0.6 | 3.5 ± 3.7 | 2.2 ± 2.9* |
IADL | 0.1 ± 0.4††† | 0.8 ± 0.7 | 7.6 ± 5.1 | 6.6 ± 4.3 |
Cornell Depression Scale | 2.2 ± 1.7††† | 1.3 ± 1.6** | 5.2 ± 3.3 | 3.2 ± 3.2*** |
Sleep score (sum of 20 SDSQ ratings)§ | 22.5 ± 6.8 | 15.9 ± 7.6*** | 23.3 ± 8.6 | 14.7 ± 7.8*** |
Number of endorsed symptoms | 7.6 ± 2.6 | 5.0 ± 2.9*** | 7.4 ± 2.9 | 4.5 ± 2.8*** |
Estimated nighttime time in bed (TIB in h) | 8.1 ± 1.2††† | 8.1 ± 1.1 | 9.3 ± 1.8 | 9.0 ± 1.4 |
Percentage of group with ≤ 6 h TIBa | 8.2 | 5.6 | 2.8 | 3.8 |
Non-demented elderly (NDE) are healthy elderly subjects with normal cognitive function at the time of sleep symptom assessment. Poss/prob AD: individuals met NINCDS-ADRDA criteria for possible or probable Alzheimer’s disease. Sample sizes given reflect number of respondents, however, the numbers for whom each variable were recorded varied. SP+, Endorsed ‘sleep problems’; SP−, did not endorse ‘sleep problems’; ADL, Activities of Daily Living; IADL, Instrumental Activities of Daily Living.
P ≤ 0.001;
P < 0.01;
P < 0.05 across SP+, SP− within cohort;
P < 0.001;
P < 0.01 across SP+ (across cohorts).
Chi-squared contingency test and inference tests are Mann–Whitney non-parametric comparisons of means.
‘Awakens feeling well rested’ and ‘have sleep problems’ were excluded from this score.