Table 1.
Sociodemographic, lifestyle, and health-related characteristics among participants in low and high quintiles for serum 25-hydroxyvitamin D (25(OH)D) (nmol/L), assessed at the Women’s Health Initiative Observational Study baseline (1993–1998), adjusted for month of blood draw †: the Carotenoids and Age-Related Eye Disease Study (n=1,313).
| 25(OH)D, nmol/L (median (range)) | Quintile 1 | Quintile 5 | p-value* |
|---|---|---|---|
| 30 (7, 38) | 85 (75, 165) | ||
| Demographic | |||
| Age at eye photography, years (mean (SE ‡)) | 69 (0.4) | 69 (0.4) | 0.17 |
| Ethnicity (% Non-Hispanic White) | 95 | 98 | 0.03 |
| Income, ≥ $75,000/year (%) | 11 | 22 | <0.01 |
| Study site (%) | 0.23 | ||
| Iowa | 32 | 35 | |
| Oregon | 37 | 27 | |
| Wisconsin | 32 | 38 | |
| Lifestyle | |||
| Smoking pack-years (%) | 0.22 | ||
| Never | 55 | 63 | |
| 0–7 | 21 | 21 | |
| >7 | 24 | 16 | |
| Alcohol, g/week (%) | 0.03 | ||
| Non-drinker | 46 | 36 | |
| 0.4 to < 4.0 | 33 | 29 | |
| ≥4 to < 127 | 22 | 35 | |
| Recreational physical activity, MET hrs/wk (%) | <0.01 | ||
| None – 3 | 37 | 17 | |
| 3 – 10 | 26 | 21 | |
| 10 – 21 | 20 | 27 | |
| ≥21 | 17 | 35 | |
| Average ocular visible sun exposure in the last 20 years, Maryland sun-years (mean (SE)) | 0.77 (0.03) | 0.91 (0.03) | <0.01 |
| Ocular and medical factors | |||
| Iris color (% blue) | 44 | 42 | 0.90 |
| Family history of macular degeneration (% yes) | 13 | 18 | 0.16 |
| Body mass index, kg/m2 (%) | <0.01 | ||
| < 22.5 | 10 | 30 | |
| 22.5 ≤ to < 25 | 12 | 24 | |
| 25 ≤ to < 30 | 36 | 31 | |
| 30 ≤ to < 35 | 22 | 13 | |
| 35 ≤ | 21 | 2 | |
| Hypertension (% yes) | 35 | 28 | 0.01 |
| Cardiovascular disease (% yes) | 27 | 24 | 0.67 |
| Diabetes (% yes) | 3.1 | 1.2 | 0.28 |
| Hormone replacement therapy (%) | 0.39 | ||
| Never | 37 | 27 | |
| Past | 15 | 13 | |
| Current | 49 | 60 | |
| C-reactive protein, mg/L (mean (SE)) | 5.2 (0.3) | 4.2 (0.3) | 0.03 |
P-values are for general associations. For categorical variables, the Cochran-Mantel-Haenszel statistic for a general association is used. For continuous variables, an ANOVA to compare least square means by level of categorical predictor (quintile of serum vitamin D) is used. A p-value for the ANOVA was obtained for the linear trend by replacing the categorical predictor with the continuous variable (serum vitamin D). P-values do not necessarily represent a linear trend for either type of variable. Continuous variables are adjusted for age as a continuous variable and categorical variables are adjusted for age using a variable with 3 categories (≤69; 70–74; ≥75).
Serum vitamin D values were adjusted for month of blood draw by adding the residuals from a Loess fit to the overall population mean (57.31 nmol/L).
SE =Standard Error