TABLE 1—

Participant Characteristics by Condition at Baseline: Safety and Health Involvement For Truckers (SHIFT) Randomized Controlled Trial: United States, 2012–2014

	Control (n = 223)		Intervention (n = 229)
Variables	No.	Mean (SD) or %	No.	Mean (SD) or %	P
Age, y	220	47.6 (11.6)	225	47.9 (11.2)	.80
Gender = male	190	86.0	199	86.9	.77
Race					.06
American Indian/Alaskan Native	2	0.9	4	1.8
Asian	1	0.4	0	0.0
Native Hawaiian/Pacific Islander	3	1.4	0	0.0
Black/African American	11	5.0	22	9.8
White	181	82.6	168	74.7
> 1 race	13	5.9	14	6.2
Other	8	3.7	17	7.6
Hispanica	14	6.9	28	13.3	.029
Married or living with partner	148	66.7	143	62.5	.35
Dependent children ≥ 1	66	29.9	82	36.1	.16
Education					.37
High-school diploma or GED	99	47.4	120	56.3
Vocational/technical certificate	66	31.6	50	23.5
Associate degree	26	12.4	24	11.3
Bachelor’s degree	14	6.7	15	7.0
Graduate degree	4	1.9	4	1.9
Days away per dispatcha,b	221	4.1 (1.4)	228	3.7 (1.6)	.002
Away ≥ 5 nights per dispatcha	136	61.5	114	50.0	.014
Weekly work hours					.86
0–54.99	47	21.4	43	19.4
55–64.99	84	38.2	85	38.3
≥ 65	89	40.5	94	42.3
Tenure as truck driver, y	220	11.2 (10.8)	229	11.8 (10.0)	.49
Tenure current company, y					.98
< 1	79	35.6	82	36.0
1–2.49	37	16.7	38	16.7
2.5–4.99	28	12.6	26	11.4
≥ 5	78	35.1	82	36.0
Manual material handlinga,c	222	1.3 (1.4)	228	0.9 (1.2)	.001
Smoker (past month)	65	29.3	71	31.0	.69
Health conditions
Diabetes	29	13.1	27	11.8	.68
Meds for diabetesd	23	85.2	23	88.5	.73
High blood pressurea	62	28.1	92	40.2	.007
Meds for high blood pressured	52	82.5	69	75.8	.32
Obstructive sleep apnea	48	21.6	33	14.5	.051
Treatments for obstructive sleep apnead	44	91.7	27	84.4	.70

Note. GED = general equivalency diploma. The sample size was n = 452.

^aStatistically significant between-group differences observed at baseline. For continuous variables, P values are based on a 2-sample nonparametric test. For dichotomous or categorical variables, P values are based on the χ² test. Percentage calculations are based on number of participants responding to each item and are not adjusted for missingness.

^bWe assessed days away from home per dispatch with frequency intervals of 1 = home every night; 2 = 2 to 4 days; 3 = 5 to 7 days; 4 = 8 days to 2 weeks; and 5 = more than 2 weeks.

^cWe assessed manual material handling with a 5-level frequency scale: 0 = never; 1 = more than once per year; 2 = more than once per month; 3 = 1 or more times per week; 4 = daily.

^dRows represent subsets of participants with the condition reporting some form of treatment. Levels of primary outcome variables did not significantly differ between groups at baseline.