Fig. 2
From: Genetic influence on serum 25-hydroxyvitamin D concentration in Korean men: a cross-sectional study
a Distribution of mean serum 25-hydroxyvitamin D [25(OH)D] concentration by age groups. When analyzed by linear regression, mean serum 25(OH)D concentration tended to increase with age (R2 = 0.032, p for trend < 0.001). b Prevalence of vitamin D insufficiency and deficiency by age groups. As participants’ age increased, the prevalence of vitamin D deficiency tended to decrease. (p for trend < 0.001, obtained by linear-by-linear association of chi-square test)