Table 1.

Characteristics of the BioCycle Study participants (2005–2007)

	n	%
Age (years)
Median [IQR]	24 [20–35]
Race
White	154	59.5
Black	51	19.7
Other	54	20.9
Body Mass Index (kg/m2)
Median [IQR]	23 [21–26]
Cigarette use around the LH surgea
Yes	14	5.5
Mean daily caffeine intake around the LH surge (milligrams)a
Median [IQR]	43 [1–143]
Percent of energy intake around the LH surge attributable toa,b:
Alcohol
Median [IQR]b	0
Fat
Median [IQR]	34 [26–41]
Protein
Median [IQR]	15 [12–18]
Carbohydrates
Median [IQR]	50 [42–60]
Mean daily energy intake around the LH surge (kcal)a
Median [IQR]	1515 [1245–1950]
Menses length, daysa
Median [IQR]	5 [4–6]
Season around the LH surgea
Winter	67	25.9
Spring	72	27.8
Summer	70	27.0
Fall	50	19.3
Average hours of sleep per day around the LH surge
Median [IQR]	7.0 [6.3–7.8]
Women sleeping <7 hours per day at the LH surge a	116	45.7
Employment and night/shift work status
Employed, No night/shift work	103	46.0
Unemployed	44	19.6
Employed, Yes night/shift work	77	34.4
Chronotype Scores, continuous
Median [IQR]	4.5 [3.5–6.0]
Categorized chronotype
Morning (score range 2.0 to <3.5)	47	19.2
Intermediate (≤3.6 to ≤6.0)	156	63.7
Evening (>6.0 to 23.0)	42	17.1

n=number, p=p-value, IQR=interquartile range, (kg/m²)=kilograms per meter squared, LH=luteinizing hormone, kcal=kilocalorie

The percentages in the tables reflect the proportion of women not missing information on a given characteristic. The number of women missing information: cigarette use around the LH surge, cycle 1 (n=5); daily caffeine intake around the LH surge, cycle 1 (n=7); percent of energy intake around the LH surge, cycle 1 (n=7 each for alcohol, fat, protein, and carbohydrates); daily caloric intake around the LH surge, cycle 1 (n=7); menses length in cycle 1 (n=5); night/shift work (n=35); chronotype (n=14); average daily sleep around the LH surge, cycle 1 (n=5).

^aFrom the first menstrual cycle followed for each woman

^bThe IQR for percent of diet attributable to alcohol was zero.