Peinemann et al. to our prior analysis of the effect of smoking cessation on CAC (Jöckel et al. 2009). To estimate the effect of SHS on the prevalence of any calcification (CAC > 0), we used logistic regression to derive odds ratios (ORs) for CAC > 0. In addition, we investi- gated the effect of using different CAC score cut points for defining the dichotomous out- come variable, from CAC > 0 versus CAC = 0, CAC > 1 versus CAC ≤ 1, and so forth, up to CAC > 1,000 versus CAC ≤ 1,000, and repeated the logistic regression analysis with these different response variables. As a further sensitivity analysis, we used ln(CAC + 0.1) and ln(CAC + 10) as the response variable in Baseline characteristic CACb Mean 50th percentile (median) 75th percentile Maximum value Values > 0 [n (%)] Age [years (median)] BMI [kg/m2 (median)] Physical activity, metabolic equivalents per week (median) LDL [mg/dL (median)] HDL [mg/dL (median)] Systolic blood pressure [mmHg (median)] Men [n (%)] Diabetes mellitus [n (%)] Antihypertensive drugs [n (%)]c Length of education [n (%)] ≤ 10 years 11–13 years 14–17 years ≥ 18 years Employment status [n (%)] Full-time or part-time work (≥ 15 hr/week) Inactive or housewife Pensioner Unemployed No. of smokers at home [n (%)]d 0 1 ≥ 2 Home Work Other Location of exposure Table 1. Baseline characteristics of analyzed never-smokers (n = 1,766) in the Heinz Nixdorf Recall Study according to SHS exposure status. addition to ln(CAC + 1) in linear regression models. We also estimated the percent change in CAC associated with SHS in an analysis restricted to those with measurable CAC (n = 1,150) and estimated associations between SHS and prevalent diagnosed CHD at baseline (128 cases among 1,894 partici- pants). All statistical analyses were conducted using SAS software (version 9.2; SAS Institute Inc., Cary, NC, USA). Results Self-reported frequent exposure to any SHS was reported by 21.5% of 1,766 never- smokers (Figure 1) and varied considerably by SHSa (n = 379) No SHS (n = 1,387) Total (n = 1,766) 120.9 7.0 56.2 4,790.3 248 (66.4) 57.0 27.6 579.2 146.0 55.0 131.5 146 (38.5) 46 (12.1) 123 (32.5) 62 (16.4) 216 (57.0) 70 (18.5) 31 (8.2) 194 (51.2) 54 (14.2) 103 (27.2) 28 (7.4) 203 (53.6) 151 (39.8) 25 (6.6) 1,597 1,553 1,660 171.5 7.7 99.0 5,636.3 902 (65.0) 63.0 27.2 593.6 144.0 57.0 131.5 454 (32.7) 164 (11.8) 502 (36.2) 212 (15.3) 761 (54.9) 260 (18.7) 154 (11.1) 360 (26.0) 318 (22.9) 639 (46.1) 70 (5.0) 1,284 (92.6) 96 (6.9) 7 (0.5) 169 213 106 160.06 7.7 88.7 5,636.3 1,150 (65.1) 62.0 27.3 591.6 145.0 56.0 131.5 600 (34.0) 210 (11.9) 625 (35.4) 274 (15.5) 977 (55.3) 330 (18.7) 195 (11.0) 554 (31.4) 372 (21.1) 742 (42.0) 98 (5.5) 1,487 (84.2) 247 (14.0) 32 (1.8) 1,766 1,766 1,766 age and sex, as shown by a lower median age and higher percentage of men in the exposed group (Table 1). CAC was also strongly asso- ciated with age and sex (Table 2). In the age- stratified analyses, SHS-exposed participants generally had higher CAC values and frequen- cies of CAC > 0 than did nonexposed par- ticipants. In the full cohort of never-smokers (n = 1,894), which included 128 participants with manifested CHD, CHD was more prevalent among participants reporting SHS exposure (33 of 412, 8.0%) than in those unexposed (95 of 1,482, 6.4%). In linear regression analyses, the unadjusted crude estimate [–18.6%; 95% confidence inter- val (CI): –38.0%, 7.0%] indicated an inverse association of SHS with CAC + 1 (Table 3). After adjusting for age, sex, years of education, and economic activity, CAC + 1 was 21.1% (95% CI: –5.5%, 55.2%) higher in exposed than in unexposed participants. Further adjust- ment for the cardiovascular risk factors diabetes mellitus, BMI, physical activity, and LDL:HDL attenuated the association (15.4%; 95% CI: –9.6%, 47.2%). Additional adjustment for potential intermediate variables hypertension and antihypertensive therapy decreased the esti- mate to 10.6% (95% CI: –14.3%, 42.7%). When limiting the analysis to subjects with CAC > 0 (n = 1,150), we did not see an associa- tion with SHS (data not shown). In logistic regression analysis, the OR for CAC > 0 was 1.47 (95% CI: 1.11, 1.94), adjusted for sex, age, years of education, and employment status, and 1.38 (95% CI: 1.03, 1.84) after also adjusting for diabetes, BMI, physical activity and LDL:HDL (Table 3). Adding the potential intermediate variables hypertension and antihypertensive therapy to the model decreased the OR to 1.30 (95% CI: 0.97, 1.74). Using different cut-points for dichotomizing CAC in a secondary analysis revealed that CAC > 0 versus CAC = 0 up to CAC > 10 versus CAC ≤ 10 had ORs with lower 95% confidence limits > 1.0 (data not shown). Cut-points between CAC > 20 versus CAC ≤ 20 and CAC > 800 versus CAC ≤ 800 resulted in positive effect estimates but with 95% CIs including 1.0. A linear regression model that included indicator variables for all three possible ovlume 119 | number 11 | November 2011 • Environmental Health Perspectives aSelf-reported frequent exposure to SHS at work, at home, or at other places. bDetected by EBCT; mean CAC refers to the arithmetic mean in this population. cData missing for 116. dA total of 128 participants lived with a current smoker and reported no SHS at home; 18 participants reported SHS at home and did not live with a current smoker. Table 2. Distribution of CAC among never-smokers without clinically manifested CHD (n = 1,766) according to age group and sex. Category Age group (years) 45 to < 55 55 to < 65 ≥ 65 Sex Men Women 1558 Abbreviations: P50, 50th percentile (median); P75, 75th percentile. aSelf-reported frequent exposure to SHS either at work, at home, or at other places. n (%) 143 (37.7) 152 (40.1) 84 (22.2) 146 (38.5) 233 (61.5) SHSa (n = 379) P50 1.0 9.3 42.5 36.2 1.0 P75 17.5 55.5 225.9 157.6 23.5 CAC > 0 [n (%)] 73 (51.0) 106 (69.7) 69 (82.1) 125 (85.6) 123 (52.8) No SHS (n = 1,387) Total (n = 1,766) n (%) 286 (20.6) 547 (39.4) 554 (39.9) 454 (32.7) 933 (67.3) P50 0.0 6.2 42.3 49.7 2.6 P75 7.2 72.7 203.5 247.8 51.8 CAC > 0 [n (%)] 118 (41.3) 357 (65.3) 427 (77.1) 362 (79.7) 540 (57.9) n (%) 429 (24.3) 699 (39.6) 638 (36.1) 600 (34.0) 1,166 (66.0) P50 0.0 7.2 42.4 47.7 2.1 P75 12.4 66.3 204.7 205.9 44.4 CAC > 0 [n (%)] 191 (44.5) 463 (66.2) 496 (77.7) 487 (81.2) 663 (56.9)