Table 4. Mean forearm bone mineral density (BMD) and 95% confidence intervals (95% CI) at 17 years of age according to smoking and drinking categories and adverse behaviors clusters.
| Mean (95% CI) forearm BMD at 17 years of age | |||
| N | Adjusted for menarche age and regular sports | Adjusted for menarche age, regular sports and body mass index | |
| Smoking frequency at 13 | |||
| Never tried | 523 | 0.437 (0.433, 0.442) | 0.436 (0.432, 0.440) |
| Tried but does not currently smoke | 165 | 0.425 (0.417, 0.433) | 0.426 (0.419, 0.434) |
| Smokes but not every day/Smokes at least once a day | 24 | 0.431 (0.410, 0.452) | 0.433 (0.413, 0.452) |
| p | 0.217 | 0.068 | |
| Smoking frequency at 17 | |||
| Never tried | 390 | 0.436 (0.431, 0.441) | 0.435 (0.430, 0.440) |
| Tried but does not currently smoke | 224 | 0.435 (0.428, 0.442) | 0.436 (0.429, 0.442) |
| Smokes but not every day | 33 | 0.418 (0.400, 0.436) | 0.421 (0.404, 0.438) |
| Smokes at least once a day | 72 | 0.429 (0.417, 0.441) | 0.432 (0.420, 0.443) |
| p | 0.257 | 0.438 | |
| Ever smoking in adolescence | |||
| Never smoked at17 | 353 | 0.437(0.432, 0.443) | 0.436 (0.431, 0.441) |
| Tried smoking after 13 but before 17 | 167 | 0.438 (0.430, 0.445) | 0.438 (0.431, 0.445) |
| Tried smoking before 13 years of age | 192 | 0.426 (0.418, 0.433) | 0.428 (0.421, 0.435) |
| p | 0.030 | 0.103 | |
| Drinking frequency at 13 | |||
| Never tried drinking | 298 | 0.439 (0.434, 0.445) | 0.438 (0.433, 0.444) |
| Tried but does not currently drink | 380 | 0.433 (0.428, 0.438) | 0.433 (0.428, 0.438) |
| Drinks less than once a week | 26 | 0.420 (0.400, 0.439) | 0.428 (0.410, 0.447) |
| Drinks at least once a week but not every day/Drinks every day | 8 | 0.414 (0.378, 0.449) | 0.417 (0.384, 0.449) |
| p | 0.084 | 0.282 | |
| Drinking frequency at 17 | |||
| Never tried drinking | 120 | 0.438 (0.429, 0.448) | 0.434 (0.425, 0.442) |
| Tried but does not currently drink | 273 | 0.436 (0.430, 0.442) | 0.436 (0.430, 0.442) |
| Drinks less than once a week | 266 | 0.432 (0.426, 0.438) | 0.434 (0.428, 0.439) |
| Drinks at least once a week but not every day/Drinks every day | 54 | 0.420 (0.406, 0.434) | 0.424 (0.411, 0.438) |
| p | 0.157 | 0.471 | |
| Ever drinking in adolescence | |||
| Never drank at17 | 84 | 0.447 (0.435, 0.458) | 0.441 (0.430, 0.451) |
| Tried drinking after 13 but before 17 | 213 | 0.436 (0.430, 0.443) | 0.437 (0.431, 0.444) |
| Tried drinking before 13 years of age | 419 | 0.431 (0.426, 0.436) | 0.432 (0.428, 0.437) |
| p | 0.045 | 0.216 | |
| Ever smoking or drinking before 13 | |||
| Tried none | 248 | 0.438 (0.431, 0.444) | 0.438 (0.432, 0.444) |
| Tried one | 312 | 0.437 (0.431, 0.443) | 0.436 (0.431, 0.442) |
| Tried both | 140 | 0.422 (0.413, 0.430) | 0.424 (0.416, 0.433) |
| p | 0.006 | 0.023 | |
| Behavioral cluster* at 13 years of age | |||
| Cluster 1 | 253 | 0.439 (0.433, 0.446) | 0.438 (0.432, 0.444) |
| Cluster 2 | 354 | 0.432 (0.427, 0.438) | 0.433 (0.428, 0.438) |
| Cluster 3 | 19 | 0.436 (0.412, 0.459) | 0.439 (0.417, 0.461) |
| p | 0.307 | 0.399 | |
P-values were calculated using one-way ANOVA.
*
Behavioral clusters defined using the following variables: sports activities, fruit intake, sleeping hours, time spent in sedentary activities, tobacco and alcohol use [23]. Adolescents were classified in one of three following groups according to behavioral aggregation: healthiest (cluster 1), intermediate (cluster 2) and least healthy (cluster 3).