Abstract
Several observational studies have reported an association between low levels of vitamin D (VD) and poor cognition in adults, but there is a paucity of data on such an association in adolescents. We investigated the association between VD and cognitive function or academic achievement among 1370 adolescents, who were selected from public middle schools in Kuwait, using stratified multistage cluster random sampling with probability proportional to size. Plasma 25-hydroxy VD (25-OH-D) was measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). An age-adjusted standard score (ASC), calculated from Raven’s Standard Progressive Matrices test, was used to evaluate cognitive function; academic achievements were extracted from the schools’ records. Data on various covariates were collected from the parents through a self-administered questionnaire and from the adolescents using face-to-face interviews. 25-OH-D was weakly correlated positively with ASC (ρ = 0.06; p = 0.04). Univariable linear regression analysis showed an association between 25-OH-D categories and ASC after adjusting for gender, but adjusting for parental education was sufficient to explain this association. Multivariable analysis showed no association between 25-OH-D and ASC after adjusting for potential confounders whether 25-OH-D was fitted as a continuous variable (p = 0.73), a variable that is categorized by acceptable cutoff points (p = 0.48), or categorized into quartiles (p = 0.88). Similarly, 25-OH-D was not associated with academic performance. We conclude that 25-OH-D is associated with neither cognitive function nor academic performance in adolescents.
Highlights
Low levels of serum vitamin D (VD) has become a global concern in all age groups, ethnicities, and geographical locations [1]
We evaluated the relationship between 25-OH-D level and adjusted standard score (ASC) using LOcally WEighted Scatterplot Smoothing (LOWESS) [35] after stratification by gender (Figure 2a)
Whereas the presence of VD receptors (VDR) and VD metabolizing enzymes in several brain areas that are involved in learning and memory in both humans and animals is well documented [15,16,17,18], epidemiological studies on humans have not demonstrated a clear association between VD and cognitive function, among children or adolescents
Summary
Low levels of serum vitamin D (VD) has become a global concern in all age groups, ethnicities, and geographical locations [1]. It is estimated that over 80% of the population worldwide has either insufficient or deficient levels of VD [2]. Such a high prevalence worldwide has led to a debate on VD levels that should be considered deficient or insufficient given the fact that most of those described as VD deficient do not suffer from obvious adverse health consequences [3,4,5]. It is worth noting that different organizations use different cutoff points to define VD deficiency and insufficiency, which may result in a large variation in VD status between different settings [6]. Low levels of serum VD is even more common among children and adolescents, girls in some settings [7,8].
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