Table 1. Characteristics of PER3^4/4, PER3^4/5 and PER3^5/5 Subjects (Mean±SD).

Characteristic	PER3 4/4	PER3 4/5	PER3 5/5	p*
N	52	63	14
Age	31.2±7.0	28.9±6.3	29.7±8.2	0.191
BMI (kg/m2)	25.50±3.54	24.19±3.57	23.75±2.39	0.076
Sex (M/F)	28/24	30/33	5/9	0.473
Ethnicity (Caucasian/African American/Other) #	20(.41)/31(.41)/1(.25)	24(.49)/37(.49)/2(.50)	5(.10)/8(.10)/1(.25)
Morningness-Eveningness Composite Scale	40.47±5.63a	39.00±5.44	41.86±6.50	0.154
Beck Depression Inventory (BDI)	1.35±1.96b	1.69±2.51d	1.14±2.03	0.600
Eysenck Personality Inventory (Extraversion subscale)	15.16±4.04c	15.73±3.64e	14.50±4.03	0.505
North American Adult Reading Test (IQ)	107.10±8.61c	105.30±7.97f	104.57±6.69	0.410
Sleep Onset **	23:49±0.93 hc	23:58±0.92 h	23:40±0.85 h	0.462
Sleep Offset **	07:46±0.90 hc	08:00±1.00 h	07:40±0.85 h	0.296
Sleep Midpoint **	03:58±0.35 hc	04:01±0.35 h	03:59±0.27 h	0.826
Total Sleep Time ** (Sleep Duration)	7.96±0.73 hc	8.06±0.74 h	8.00±0.55 h	0.780

^an = 49.

^bn = 51.

^cn = 50.

^dn = 62.

^en = 59.

^fn = 60.

^*p values are for the comparison of the three genotypes.

^**Determined by wrist actigraphy (one week prior to study entry).

^#Genotypic frequencies are in parentheses. 4-repeat allele frequency was 650 and 5-repeat allele frequency was 350 for both Caucasians and African Americans.