Table 1.
Baseline Characteristics of CARDIA Participants, by smoking behavior during follow-up.
| Variable | Non-smokers at baseline |
Smokers at baseline | P valuel | ||
|---|---|---|---|---|---|
| Never smokers at baseline |
Ex- smokers at baseline |
Documented smoking cessation attempt during follow-up |
No documented smoking cessation attempt throughout follow-upk |
||
| N, (% of total ) a | 2,843 (56) | 678 (14) | 923 (18) | 633 (12) | |
|
Demographics - Age, mean (SD), y |
24.5 (3.7) | 25.9 (3.2) | 25.0 (3.7) | 25.0 (3.6) | <0.01 |
| - Race-sex, No. (%)b Black women |
878 (31) | 128 (19) | 294 (32) | 172 (27) | <0.01 |
| Black men | 614 (22) | 106 (16) | 233 (25) | 192 (30) | |
| White women | 682 (24) | 262 (38) | 203 (22) | 154 (24) | |
| White men | 669 (24) | 182 (27) | 193 (21) | 115 (18) | |
| - College-education at
any examination , No (%) |
1222 (43) | 271 (39) | 162 (18) | 95 (15) | <0.01 |
| - Married, No. (%) | 631 (22) | 200 (29) | 180 (20) | 118 (19) | <0.01 |
|
Physical activity - Total physical activity score, median (IQR)c |
425 (396) | 444 (393) | 411 (355) | 389 (353) | <0.01 |
| - Leisure-time physical
activity score, median (IQR)c |
386 (374) | 401 (356) | 358 (323) | 337 (324) | <0.01 |
| - Ocupation-related
physical activity score, media (IQR)c |
40 (42) | 45 (54) | 52 (72) | 52 (84) | <0.02 |
| - Physical activity level
before high school, mean (SD)d |
3.9 (2) | 3.8 (2) | 3.9 (2) | 3.9 (2) | 0.04 |
|
Smoking variables - Cigarettes per day, median (IQR) |
- | 10 (16) e | 10 (15) | 10 (13) | <0.01 |
| - Years of smoking. median (IQR)f | - | 4.8 (5) | 8.4 (6) | 8.7 (7) | <0.01 |
| - Age at smoking start, mean (SD) | - | 17 (3) | 16 (3) | 16 (3) | 0.9 |
|
Alcohol use
g - Abstainer |
1356 (48) | 229 (34) | 244 (26) | 149 (24) | <0.01 |
| - Light to moderate | 1449 (51) | 420 (63) | 610 (66) | 444 (70) | |
| - Heavy | 30 (1) | 22 (3) | 68 (7) | 37 (6) | |
|
Self-reported significant
medical condition interfering with physical activity at examination 7 h |
330 (14) | 116 (22) | 92 (13) | 60 (13) | <0.01 |
|
Self-reported depression
(CES-D) at examination 5 i |
431 (19) | 154 (20) | 223 (27) | 124 (31) | <0.01 |
|
Anthropomorphic
variables - BMI, mean (SD)j |
24.6 (5.1) | 24.2 (4.5) | 24.4 (4.9) | 24.4 (5.4) | <0.01 |
Abbreviations: BMI: body mass index; CARDIA, Coronary Artery Risk Development in Young Adults study; CES-D: Center for Epidemiologic Studies Depression scale; IQR, interquartile range; SD, standard deviation
36 participants had missing information on smoking status at baseline and are thus excluded from this table.
By design, the CARDIA study sampled self-identified white men, white women, black men and black women in roughly equal numbers for participation in the study.(3)
See Appendix table 1 for detailed description of elements included in the score ( maximum score: 2055).
Self-reported score on a scale from 1-5: 1 corresponding to physically inactive and 5 to very active.(3) 4 missing values for physical activity level before high school.
Self-reported number of cigarettes smoked while still a smoker.
Years of smoking counted as each years of follow-up where participants were coded as current smokers. Years of smoking at baseline were added to the years of smoking at each examination based on the self-report years of smoking at baseline. 13 missing self-reported years of smoking at baseline.
Categories of alcohol consumption were based on the sex-specific weekly maximum drinking limits published by the National Institute on Alcohol Abuse and Alcoholism [for men >14 (women >7) standard drinks/week or >4 (>3) drinks/day].(22)
At examination year 7 through 25, participants were specifically asked to report if they had a medical condition interfering with ability to exercise and to grade how much this condition interfered on a scale from 1 (a little) to 5 (very much). A score of more than 2 was considered significant for the present analyses.
Self-reported depression was measured every five years starting at year 5 examination by using the Center for Epidemiologic Studies Depression scale (CES-D).(23) A score of ≥16 used as the cut-off value for both sexes as an indication of the clinically significant depressive symptoms.(24)
Calculated as weight in kilograms divided by height in meters squared.
Smokers throughout follow-up were smokers who had no documented change in smoking status from study start until the year 25 examination or until they were lost to follow-up.
P values are from a 1-way analysis of variance for age, BMI and age at smoking start; from a χ2 test for race-sex, education, center, income, marital status, significant self-reported medical condition interfering with physical activity and alcohol use category; and from a Kruskal-Wallis nonparametric test for leisure-time physical activity, cigarettes smoked per day and years of smoking. All P values are two sided.