Table 1.

Subject characteristics (mean ± SD).

	Older subjects (> 50y; n = 14)	Younger subjects (20–30y; n = 16)	p value
Age	59.6 ± 5.7	23.1 ± 3.3	–
Laterality (right-handed)	14	16
Sex	6M/8F	9M/7F	0.46
Body mass index (BMI)	24.9 ± 4.3	23.3 ± 3.4	0.29
Depression score (BDI-II)	2.1 ± 3.2	2.4 ± 2.6	0.73
Anxiety score (BAI)	0.9 ± 0.6	2.2 ± 3.3	0.10
Daytime propensity to fall asleep (Epworth)	6.7 ± 3.9	5.6 ± 3.9	0.42
Sleep disturbance score (PSQI)	2.5 ± 1.9	2.8 ± 1.7	0.64
Chronotype score (MEQ)	65.8 ± 6	48.3 ± 7.6	0.52
Years of education	14.9 ± 3	15.8 ± 2.4	0.36
Coffee/Tea intake per week (cup)	12.1 ± 8.3	7.5 ± 6.7	0.15
Alcohol intake per week (glass)	2.5 ± 2.2	2.3 ± 2.3	0.75
Ratio of women using hormonal contraceptive	0/8	5/7	< 0.001*
Ratio of women using hormonal replacement therapy	1/8	0/7	0.25
Date of study (dd/mm/yy)	08/11/09 ± 28d	07/11/09 ± 29d	0.88
Bedtime prior to experiment
PSQI-week	22:34 ± 0:55	24:02 ± 0:33	< 0.001*
Sleep diary	22:36 ± 0:44	24:03 ± 0:41	< 0.001*
Wake time prior to experiment
PSQI-week	6:49 ± 0:43	8:40 ± 0:59	< 0.001*
Sleep diary	6:55 ± 0:59	8:31 ± 0:59	< 0.001*
Total sleep time prior to experiment (h:min) (PSQI-week)	6:49 ± 0:43	8:12 ± 0:48	< 0.002*

BDI-II beck depression inventory-II, BAI beck anxiety inventory, PSQI Pittsburgh sleep quality index, MEQ morningness–eveningness questionnaire.