Solar ultraviolet-B radiation and vitamin D: a cross-sectional population-based study using data from the 2007 to 2009 Canadian Health Measures Survey

Table 4 Multivariable linear regression model for 91-day UV-B and square root transformed 25(OH)D within subgroups of age and physical activity index, weighted for the household population aged 12 to 79 years, Canada, 2007 to 2009

Effect Modifier	β* ± SE	Mean 25(OH)D**	P	Model	Partial
	β* ± SE	(95% CI)		r²	r²***
Age
12-19 years	0.07 ± 0.01	0.9 (0.6, 1.3)	< 0.0001	0.27	0.07
20-59 years	0.04 ± 0.01	0.6 (0.3, 0.9)	0.0001	0.22	0.03
60-79 years	−0.01 ± 0.01	−0.1 (−0.5, 0.2)	0.54	0.09	<0.01
Physical Activity Index
Inactive	0.03 ± 0.01	0.5 (0.0, 0.8)	0.0009	0.20	0.02
Moderately Active	0.03 ± 0.01	0.4 (0.1, 0.8)	0.02	0.19	0.01
Active	0.06 ± 0.02	0.9 (0.4, 1.3)	0.0001	0.19	0.07

Adjusted for sex, age, ethnicity, sun exposure, vitamin D supplementation, milk consumption, BMI, and PAI.
*Estimated mean increase in square root transformed 25(OH)D for a 1 kJ/m² increase in solar UV-B irradiance between 11 am and 4 pm at the CHMS collection sites averaged over the 91-days prior to blood draw (91-day UV-B).
**Estimated mean change in back transformed 25(OH)D (nmol/L) for a 1 kJ/m² increase in solar UV-B irradiance between 11 am and 4 pm for the CHMS collection sites averaged over the 91-days prior to blood draw (91-day UV-B).
***Total variance in square root transformed 25(OH)D explained by 91-day UV-B, controlling for all other variables.

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