The mean (SD) seasonally adjusted serum 25(OH)D3, phosphate and albumin-adjusted calcium concentration were 62.1 (0.8) nmol/l, 1.53 (0.16) mmol/l and 2.38 (0.12) mmol/l, respectively. The median (IQR) for serum 25(OH)D2 and PTH were 3.2 (1.3–6.7) nmol/l and 4.4 (3.3–5.8) pmol/l, respectively. Mean (SD) score in KS3 English, maths and science examinations were 54 (15), 89 (20) and 102 (22), respectively.
Supplementary table 1 shows the distribution of outcomes and confounders in participants with data on outcomes who were excluded due to missing data in exposures or confounders and in complete cases. Complete cases were more likely to perform better in both KS examinations, have higher IQ and lower BMI, to be of white ethnicity, less meticulous about protection from UVB and from higher socioeconomic backgrounds than those with missing data on exposures or confounders.
Supplementary table 2 shows the associations of potential confounders with 25(OH)D2, 25(OH)D3, PTH, calcium and phosphate. Those with non-white ethnicity had higher PTH and lower 25(OH)D3 and 25(OH)D2 concentrations. BMI was negatively associated with serum 25(OH)D3 and positively with PTH concentrations. Higher socioeconomic position was associated with higher concentrations of 25(OH)D3 and phosphate and lower concentrations of 25(OH)D2 and calcium. Children who were protected more from UVB exposure had lower 25(OH)D3, phosphate and PTH concentrations and higher calcium concentrations. Time spent outdoors during summer was positively associated with 25(OH)D3 concentrations. Pupils who were eligible for free school meals had lower 25(OH)D3 and higher 25(OH)D2 and PTH concentrations.
Supplementary table 3 shows the associations of potential confounders with KS3 scores. Non-white ethnicity, higher BMI, lower socioeconomic position, being more meticulous about avoiding UVB exposure and spending less time outdoors were all associated with lower examination scores in at least one of English, maths or science. Supplementary table 4 summarises the associations of potential confounders and academic performance in KS4. In general, these associations were similar to those found with KS3 scores.
shows the prospective associations of serum 25(OH)D3, 25(OH)D2, calcium, phosphate and PTH concentrations with KS3 scores. 25(OH)D3 concentrations were not associated with any KS3 outcomes. Higher 25(OH)D2 concentrations were associated with worse performance in English in the unadjusted model (model 1) and after adjusting for confounders including ethnicity, socioeconomic position, protection from UVB (model 2) and for other analytes, including 25(OH)D3 (model 3). 25(OH)D2 was not associated with performance in maths or science. The associations of 25(OH)D3 and 25(OH)D2 with English were different from each other (p=0.01). None of PTH, calcium or phosphate was associated with KS3 outcomes in confounder-adjusted models.
Prospective association of 25(OH)D3, 25(OH)D2, phosphate, calcium and PTH concentrations (assessed at mean age of 9.8 years with key stage 3 scores (assessed at age 13–14 years) (n=3171)
shows the prospective association between exposures and KS4 outcomes. These were essentially consistent with findings seen for KS3 outcomes. 25(OH)D3 was not associated with any of the KS4 outcomes, and higher serum 25(OH)D2 concentrations were associated with worse academic performance (less likely to obtain ≥5 A*–C grades or ≥9 A*–A grades) in the unadjusted model (model 1). These inverse associations attenuated slightly with adjustment for potential confounders (model 2), with additional adjustment for other analytes, including 25(OH)D3 not changing results further (model 3). There was statistical evidence that the associations of 25(OH)D3 and 25(OH)D2 with obtaining ≥5 A*–C grades differed from each other (p=0.02). PTH, calcium and phosphate concentrations were not associated with any KS4 outcomes, with the exception of phosphate having a modest positive association with obtaining ≥5 A*–C grades. The associations of unadjusted (for season) 25(OH)D3 and total 25(OH)D concentrations with educational outcomes were similar to those of season-adjusted 25(OH)D3 shown here (supplementary tables 5 and 6).
Prospective association of 25(OH)D3, 25(OH)D2, phosphate, calcium and PTH concentrations (assessed at mean age of 9.8 years) with key stage 4 educational attainment (age 15–16 years) (n=3171)
Supplementary tables 7 and 8 show the results of sensitivity analyses restricted to participants with data on IQ at age 8.5 years and exposure measurements at age 9.9 or 11.8 years. Adjustment for IQ at age 8.5 years, in addition to other confounders, did not alter the inverse associations of 25(OH)D2 with outcomes.