Table 1.

Selected characteristics of cortisol data collection by demographic characteristics for MESA Stress Study participants

	Percent distribution of participants	Percent of participants with 5 or more samples on all daysa	Percent of samples with reported times within 15 minutes of track-caps times b	Percent of days for which 1st sample was taken within 5 minutes of wakeupc	First sample time (median)	Last sample time (median)	Difference between 1st and 2nd sample time (median)	Cortisol area under the curved (median)
ALL SUBJECTS (N=935)	100.0%	85.2%	86.0%	78.2%	6:42	22:26	0:34	6270
SITE
New York	51.9%	86.0%	86.6%	77.7%	6:49	22:46	0:34	6403
Los Angeles	48.1%	84.4%	85.1%	78.7%	6:36	22:07	0:35	6112
p-value e		0.5085	0.0084	0.5146	0.0683	0.0313	0.5319	0.4893
AGE
48–54	17.0%	86.8%	87.1%	88.4%	6:33	22:45	0:33	5562
55–64	31.1%	85.2%	86.9%	77.6%	6:32	22:24	0:34	6122
65–74	33.1%	86.7%	86.0%	76.6%	6:47	22:25	0:36	6380
75–89	18.8%	81.3%	82.9%	72.8%	6:53	22:23	0:35	6924
p-value e		0.2638	<.0001	<.0001	0.0051	0.1615	0.3855	0.0003
SEX
Female	51.6%	84.2%	86.1%	79.2%	6:40	22:25	0:35	5859
Male	48.5%	86.3%	85.7%	77.2%	6:45	22:29	0:34	6689
p-value e		0.3699	0.5702	0.2027	0.9091	0.0750	0.0595	0.1030
RACE
White	19.6%	85.3%	89.1%	86.2%	6:45	22:44	0:33	7048
Black	27.6%	84.9%	85.2%	73.4%	6:58	22:51	0:35	6300
Hispanic	52.8%	85.4%	85.1%	77.7%	6:32	22:10	0:35	5935
p-value e		0.9804	<.0001	<.0001	0.6883	0.1798	0.1514	0.0017
TOTAL GROSS FAMILY INCOME
<$25,000	39.5%	83.0%	82.8%	73.4%	6:45	22:05	0:37	6152
$25–49,999	32.6%	88.9%	87.6%	80.2%	6:39	22:37	0:34	6208
>=$50,000	27.9%	85.0%	88.5%	83.1%	6:42	22:44	0:33	6543
p-value e		0.3694	<.0001	<.0001	0.1008	0.0035	0.5271	0.8716
WEALTH
0 Assets	18.2%	82.9%	83.9%	75.3%	6:48	22:13	0:37	6167
1 Assets	25.2%	85.2%	83.0%	78.6%	6:42	22:32	0:34	6157
2 Assets	24.2%	86.3%	86.5%	79.3%	6:38	22:21	0:34	6219
3 Assets	20.2%	86.8%	89.7%	79.5%	6:42	22:26	0:34	6292
4 Assets	12.2%	84.2%	87.3%	77.4%	6:41	22:35	0:34	6696
p-value e		0.5391	<.0001	0.3203	0.0846	0.3911	0.6958	0.6506
INCOME - WEALTH INDEX
0–1 points	19.6%	84.2%	81.4%	75.2%	6:42	22:13	0:39	5923
2–3 points	28.9%	84.0%	83.9%	75.8%	6:47	22:07	0:35	6105
4–6 points	36.3%	87.3%	88.8%	80.9%	6:37	22:34	0:34	6403
7–8 points	15.2%	84.5%	88.3%	79.6%	6:46	22:41	0:34	6682
p-value e		0.5346	<.0001	0.0097	0.0798	0.0542	0.4611	0.3693
EDUCATION
<= Completed HS/GED	48.0%	82.6%	83.3%	74.8%	6:37	22:06	0:36	6118
Some College - Associate Degree	28.3%	89.1%	88.1%	79.5%	6:42	22:42	0:34	6119
>= Bachelor's Degree	23.6%	86.0%	88.4%	83.4%	6:51	22:50	0:33	6748
p-value e		0.1289	<.0001	<.0001	0.9702	0.0067	0.8616	0.3164

^a97% of participants had data for all three days.

^bBased on 15774 samples with both form and cap times.

^cBased on 2774 days with daily questionnaire information on whether first sample was collected at wake-up. Ninety-eight percent of days had this information on the survey to use.

^dThe area under the curve (AUC) was calculated using the trapezoidal rule. AUC was calculated for each day and then averaged across all 3 days using time since wake up in minutes. Cortisol values were interpolated at 16 hours to ensure all participants contributed the same amount of time to the AUC measure. Only days with 3 or more samples were used. AUC is measured in units of nmol/L*minutes.

^eP-values are calculated using chi-square tests and anovas (age, income, and education are trend tests)