Table 3.
Linear regression analyses, adjusted for sex and age, for the assessment of determinants of hair cortisol concentrations in adolescents.
| Characteristic (n) |
Linear regression adjusted for sex and age |
|
|---|---|---|
| Estimate (95% CI) | p-value | |
| Sociodemographic variables | ||
| Sex | ||
| Boys (191) | reference | |
| Girls (228) | 1.12 (0.96, 1.31) | 0.138 |
| Age (years) | 0.221 | |
| [13.5–14.5] years (113) | reference | |
| [14.5–15.5] years (273) | 1.07 (0.90, 1.28) | 0.426 |
| >15.5 years (33) | 1.32 (0.97, 1.79) | 0.083 |
| Country of birth | 0.356 | |
| Belgium (337) | reference | |
| EU (35) | 0.86 (0.65, 1.14) | 0.309 |
| Outside EU (46) | 1.12 (0.87, 1.44) | 0.382 |
| Household educational attainment | 0.835 | |
| Primary (24) | reference | |
| Secondary (139) | 1.11 (0.79, 1.55) | 0.564 |
| Tertiary (249) | 1.08 (0.77, 1.50) | 0.667 |
| Equivalent income (monthly) | 0.422 | |
| 0–1250 Euro (89) | reference | |
| 1251–1600 Euro (73) | 1.09 (0.85, 1.39) | 0.512 |
| 1601–2000 Euro (71) | 0.99 (0.78, 1.27) | 0.963 |
| >2000 Euro (118) | 0.89 (0.72, 1.11) | 0.321 |
| Perceived income adequacy | 0.194 | |
| Difficult (119) | reference | |
| Rather easy (133) | 0.91 (0.74, 1.11) | 0.333 |
| Easy to very easy (160) | 0.84 (0.69, 1.01) | 0.070 |
| Area deprivation index | 0.714 | |
| 0–5.3% (103) | reference | |
| 5.4–9.3% (105) | 0.99 (0.79, 1.23) | 0.397 |
| 9.4–15.5% (103) | 1.04 (0.83, 1.29) | 0.743 |
| >15.5% (107) | 1.11 (0.89, 1.38) | 0.349 |
| Urbanicity | 0.177 | |
| Cities (57) | reference | |
| Towns and suburbs (303) | 0.86 (0.68, 1.07) | 0.177 |
| Rural areas (59) | 0.76 (0.57, 1.02) | 0.064 |
| Population density | ||
| <600/km2 (268) | reference | |
| ≥600/km2 (151) | 1.18 (1.00, 1.38) | 0.047 |
| Lifestyle variables | ||
| Smoking | 0.967 | |
| Never or once (400) | reference | |
| Less than daily (8) | 1.02 (0.58, 1.80) | 0.932 |
| Daily (10) | 1.07 (0.64, 1.77) | 0.804 |
| Alcohol use | 0.542 | |
| Never (263) | reference | |
| Less than monthly (93) | 0.93 (0.77, 1.13) | 0.466 |
| Monthly or more (61) | 1.08 (0.86, 1.36) | 0.520 |
| Active sportsa | 0.201 | |
| Never, occasionally (63) | reference | |
| 1–2 times/week (152) | 1.24 (0.98, 1.57) | 0.073 |
| >2 times/week (202) | 1.17 (0.93, 1.47) | 0.183 |
| Hair washing frequency | 0.766 | |
| Daily (67) | reference | |
| ≥2 times a week (237) | 0.96 (0.77, 1.20) | 0.722 |
| <2 times a week (114) | 1.02 (0.80, 1.31) | 0.847 |
| Hair treatment | ||
| No (409) | reference | |
| Yes (6) | 0.72 (0.37, 1.38) | 0.321 |
| Health characteristics | ||
| Body mass Indexb | 0.297 | |
| Normal weight (302) | reference | |
| Underweight (34) | 0.89 (0.67, 1.19) | 0.433 |
| Overweight, obese (83) | 1.13 (0.93, 1.37) | 0.226 |
| Waist circumference | 0.298 | |
| ≤ 68 cm (101) | reference | |
| 68–72 cm (109) | 1.11 (0.89, 1.38) | 0.342 |
| 72–78 cm (101) | 1.19 (0.95, 1.49) | 0.121 |
| >78 cm (106) | 1.21 (0.98, 1.51) | 0.082 |
| Infections (past year) | ||
| No (162) | reference | |
| Yes (244) | 0.94 (0.80, 1.10) | 0.450 |
| Atopic diseasec | ||
| No (281) | reference | |
| Yes (129) | 1.17 (0.99, 1.38) | 0.071 |
| Corticosteroid medication | ||
| No (409) | reference | |
| Yes (8) | 0.92 (0.52, 1.62) | 0.771 |
| Menarcheal status (girls) | ||
| Pre-menarche (23) | reference | |
| Post-menarche (205) | 1.61 (1.17, 2.23) | 0.004 |
| Oral contraceptives (girls) | ||
| No (189) | reference | |
| Yes (39) | 1.01 (0.78, 1.32) | 0.927 |
| SDQ Total difficulties | 0.714 | |
| Normal (0–15) (325) | reference | |
| Borderline (16–19) (57) | 0.99 (0.79, 1.24) | 0.915 |
| Abnormal (20–40) (35) | 1.12 (0.84, 1.50) | 0.430 |
| SDQ Prosocial scale | 0.592 | |
| Normal (6–10) (381) | reference | |
| Borderline (5) (22) | 1.12 (0.80, 1.59) | 0.509 |
| Abnormal (0–4) (14) | 0.85 (0.55, 1.31) | 0.457 |
| Perceived stress | 0.382 | |
| Low (113) | reference | |
| Medium (164) | 1.05 (0.87, 1.28) | 0.607 |
| High (139) | 0.92 (0.75, 1.13) | 0.449 |
| Optimal vitalityd | ||
| No (360) | reference | |
| Yes (56) | 0.76 (0.61, 0.95) | 0.015 |
| Perceived happiness | ||
| Low (34) | reference | |
| High (382) | 0.99 (0.74, 1.31) | 0.918 |
| Preterm birth (<37 weeks) | ||
| No (387) | reference | |
| Yes (25) | 1.07 (0.77, 1.48) | 0.704 |
| Low birth weight (<2.5 kg) | ||
| No (372) | reference | |
| Yes (24) | 0.94 (0.67, 1.33) | 0.735 |
| Maternal smoking during pregnancy | ||
| No (354) | reference | |
| Yes (58) | 1.02 (0.82, 1.28) | 0.833 |
| Meteorology | ||
| 3-month average temperature | 0.459 | |
| <6°C (148) | reference | |
| 6–12°C (179) | 0.98 (0.82, 1.17) | 0.836 |
| >12°C (92) | 1.12 (0.91, 1.38) | 0.301 |
| 3-month average UV radiation | 0.659 | |
| <300 J/m2 (137) | reference | |
| 300–1000 J/m2 (123) | 0.98 (0.80, 1.20) | 0.855 |
| >1000 J/m2 (159) | 1.07 (0.89, 1.28) | 0.498 |
| Season of sampling | 0.633 | |
| Winter (136) | reference | |
| Spring (186) | 1.01 (0.84, 1.21) | 0.921 |
| Summer (0) | - | - |
| Fall (97) | 1.10 (0.89, 1.36) | 0.370 |
| Effect modification by sex | ||
| Urbanicity x Sex | 0.011 | |
| Population density x Sex | 0.024 | |
Estimates (β) are presented with their 95% confidence intervals (95% CI) as the factor change in HCC compared to the HCC of the reference category or to the opposite situation for dichotomous (yes/no) variables. Significant associations are marked in bold. aphysical activity that causes sweating and/or heavy breathing, bBody Mass Index classes based on age- and sex-specific Belgian growth curves, cdoctor-diagnosed asthma and/or atopic dermatitis and/or allergic rhinitis, dvitalityscore above the cut-off value of study population mean plus one standard deviation. EU, European Union; SES, socioeconomic status; SDQ, Strengths and Difficulties Questionnaire.