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. Author manuscript; available in PMC: 2015 Mar 24.
Published in final edited form as: J Sleep Res. 2006 Mar;15(1):97–103. doi: 10.1111/j.1365-2869.2006.00499.x

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.