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Plasma 25-hydroxyvitamin D concentration and risk of type 2 diabetes and pre-diabetes: 12-year cohort study
(complete study on link)
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193070
Introduction
The public health impact of vitamin D deficiency has received attention due to the discovery of associations between low plasma concentrations of vitamin D metabolites and higher risk of several cancers, cardiovascular disease, bone fractures [1–3] and the metabolic syndrome [4]. Trends in energy intake and anthropometric characteristics have paralleled the increase in incidence of type 2 diabetes mellitus. It is unclear whether vitamin D deficiency might be contributing to increased risk [5].
If defining 25(OH)D levels < 32 ng/ml (< 80 nmol/L) as deficiency [6], 77% of U.S. adults were deficient. The prevalence of vitamin D deficiency by this criterion has doubled since 1980 in U.S. adults [6].
Several cohort studies have examined the association of circulating 25(OH)D concentrations with risk of diabetes. Of these, 12 found significantly higher incidence rates in individuals with lower circulating 25(OH)D concentrations [5, 7–16]. The association in one was limited to overweight subjects [16]; and the significant finding in another [14] was limited to women. One study found a benefit of 25(OH)D ≥ 11 ng/ml compared to < 11 ng/ml, but no further benefit with higher concentrations [15]. Two studies reported a significant inverse association in men, but not women [17, 18]. One study reported a favorable association that did not reach statistical significance [19]. A study by Schafer et al. reported a statistically significant inverse association between 25(OH)D and hazard ratio of diabetes after adjustment for age and clinic location, but that was weak and no longer statistically significant after adjustment for more factors that included BMI [20].
The association of plasma 25(OH)D deficiency with risk of diabetes also has been examined in four meta-analyses [11, 13, 21, 22], and all reported an inverse association of circulating 25(OH)D with risk of diabetes.
The aim of this study was to examine whether lower concentrations of 25(OH)D or 1,25(OH)2D were associated with higher incidence of diabetes and pre-diabetes in a prospective cohort study with an overall follow-up period of 12 years.
This cohort may have a lower than usual prevalence of vitamin D deficiency due to year-round sunshine and good weather in a sunny and clear area of southern California [23]. It may also be possible that the cohort has a lower than usual prevalence of vitamin D deficiency due to a higher standard of education and socioeconomic status and a high proportion of Caucasians. This cohort has the highest known published median 25(OH)D concentration, 42 ng/ml or 105 nmol/L in men [24] and 39 ng/ml or 98 nmol/L in women [25] of any population that has reported data on diabetes incidence by 25(OH)D. No previous study of the association of 25(OH)D with diabetes has included a substantial population in the high range of > 30 ng/ml or 75 nmol/L.
(complete study on link)
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193070
Introduction
The public health impact of vitamin D deficiency has received attention due to the discovery of associations between low plasma concentrations of vitamin D metabolites and higher risk of several cancers, cardiovascular disease, bone fractures [1–3] and the metabolic syndrome [4]. Trends in energy intake and anthropometric characteristics have paralleled the increase in incidence of type 2 diabetes mellitus. It is unclear whether vitamin D deficiency might be contributing to increased risk [5].
If defining 25(OH)D levels < 32 ng/ml (< 80 nmol/L) as deficiency [6], 77% of U.S. adults were deficient. The prevalence of vitamin D deficiency by this criterion has doubled since 1980 in U.S. adults [6].
Several cohort studies have examined the association of circulating 25(OH)D concentrations with risk of diabetes. Of these, 12 found significantly higher incidence rates in individuals with lower circulating 25(OH)D concentrations [5, 7–16]. The association in one was limited to overweight subjects [16]; and the significant finding in another [14] was limited to women. One study found a benefit of 25(OH)D ≥ 11 ng/ml compared to < 11 ng/ml, but no further benefit with higher concentrations [15]. Two studies reported a significant inverse association in men, but not women [17, 18]. One study reported a favorable association that did not reach statistical significance [19]. A study by Schafer et al. reported a statistically significant inverse association between 25(OH)D and hazard ratio of diabetes after adjustment for age and clinic location, but that was weak and no longer statistically significant after adjustment for more factors that included BMI [20].
The association of plasma 25(OH)D deficiency with risk of diabetes also has been examined in four meta-analyses [11, 13, 21, 22], and all reported an inverse association of circulating 25(OH)D with risk of diabetes.
The aim of this study was to examine whether lower concentrations of 25(OH)D or 1,25(OH)2D were associated with higher incidence of diabetes and pre-diabetes in a prospective cohort study with an overall follow-up period of 12 years.
This cohort may have a lower than usual prevalence of vitamin D deficiency due to year-round sunshine and good weather in a sunny and clear area of southern California [23]. It may also be possible that the cohort has a lower than usual prevalence of vitamin D deficiency due to a higher standard of education and socioeconomic status and a high proportion of Caucasians. This cohort has the highest known published median 25(OH)D concentration, 42 ng/ml or 105 nmol/L in men [24] and 39 ng/ml or 98 nmol/L in women [25] of any population that has reported data on diabetes incidence by 25(OH)D. No previous study of the association of 25(OH)D with diabetes has included a substantial population in the high range of > 30 ng/ml or 75 nmol/L.
