Comparison of serum 25(OH)D levels in 5,571 young children stratified by age, season or gender.

<p>Values of serum 25(OH)D levels were compared using Mann–Whitney U test.</p><p>^a significant difference between children aged 1y and aged 2y (P<0.001).</p><p>^b Significant difference between children aged 1y and aged 3y (P<0.001).</p><p>^c Significant difference between children aged 2y and aged 3y (P<0.001).</p><p>^d No significant difference between spring and summer (P = 0.076).</p><p>^e Significant difference between spring and autumn (P<0.001).</p><p>^f No significant difference between spring and winter (P = 0.098).</p><p>^g Significant difference between summer and autumn (P<0.001).</p><p>^h Significant difference between summer and winter (P = 0.001).</p><p>ⁱ Significant difference between autumn and winter (P = 0.003).</p><p>^j No significant difference between boys and girls (P = 0.121).</p><p>Comparison of serum 25(OH)D levels in 5,571 young children stratified by age, season or gender.