Vitamin D Deficiency and Cardiovascular Disease Risk Factors Among American Indian Adolescents: The Strong Heart Family Study

Abstract

Introduction: We aimed to describe the prevalence of vitamin D deficiency among American Indian adolescents and determine its association with cardiovascular disease (CVD) risk factors.

Methods: Our study population consisted of 307 adolescents (aged ≤20 years) participating in the Strong Heart Family Study with serum 25-hydroxyvitamin D (25[OH]D) measured on samples collected during baseline examinations (2001-2003). We defined baseline prevalence of vitamin D deficiency as 25(OH)D ≤20 ng/mL. We evaluated outcomes related to obesity (BMI, waist circumference, wait-to-hip ratio, and body fat percentage), diabetes, cholesterol, and metabolic syndrome. We used generalized estimating equations to determine whether the prevalence of the outcomes differed according to vitamin D deficiency status, while controlling for covariates. To determine incidence, we conducted a follow-up examination a median 5.8 years after baseline (2006-2009) and a second follow-up a median of 13.3 years after baseline (2014-2018). We calculated incidence rates (IR) per 100 person-years for the total group and stratified by vitamin D deficiency status at baseline. Finally we used shared frailty cox proportional hazards models to determine if the risk of the outcomes differed according to vitamin D deficiency status, while controlling for covariates.

Results: The prevalence of vitamin D deficiency was 50.8% at baseline, and it was associated with the prevalence of obesity, low HDL-C, and metabolic syndrome, while controlling for covariates. By the first follow-up, the IRs per 100 person-years were the following: obesity (5.03), diabetes (1.07), any dyslipidemia (10.80), and metabolic syndrome (3.31). By the second follow-up, the IR of diabetes was significantly higher among those with (vs without) baseline vitamin D deficiency (1.32 vs 0.68 per 100 person-years; P = .02), although the association was not significant after adjusting for covariates.

Conclusion: Vitamin D deficiency in adolescence may be associated with the CVD risk factors obesity, low HDL-C, and metabolic syndrome and may also contribute to the development of diabetes later in life.

Figure 1

Baseline cross-sectional association between prevalence of vitamin D deficiency and prevalence of CVD risk factors among American Indian adolescents, Strong Heart Family Study. All models accounted for the correlated family structure; see text for definitions of risk factors and details on how models were adjusted. Abbreviations: HDL-C, high-density lipoprotein cholesterol; IFG, impaired fasting glucose; LDL-C, low-density lipoprotein cholesterol; POR, prevalence odds ratio.

Figure 2

Association between vitamin D deficiency and development of cardiovascular disease risk factors among American Indian adolescents, Strong Heart Family Study. For each model, those who had the risk factor at baseline were excluded, and all outcomes were directly measured at the first follow-up (except for diabetes) at second follow-up. All models accounted for the correlated family structure; see text for definitions of risk factors and details on how models were adjusted. Abbreviations: HR, hazard ratio; HDL-C, high-density lipoprotein cholesterol; IFG, impaired fasting glucose; LDL-C, low-density lipoprotein cholesterol.