Relationship Between Vitamin D and Hyperglycemia in Older People From a Nationally Representative Population Survey

Vasant Hirani, PhD

Disclosures

J Am Geriatr Soc. 2011;59(10):1786-1792. 

In This Article

Abstract and Introduction

Abstract

Objectives: To investigate the association between vitamin D levels and hyperglycemia in a national community sample of older people.
Design: Cross-sectional, nationally representative sample.
Setting: Community.
Participants: Two thousand thirty-eight noninstitutitionalized adults aged 65 and older taking part in the Health Survey for England 2005.
Measurements: Serum 25-hydroxy vitamin D (25(OH) D) levels, glycosylated hemoglobin (HbA1c), and covariates: age, sex, social class, season of examination, use of vitamin supplements, and physical health status.
Results: Hyperglycemia was independently associated with low vitamin D levels (odds ratio (OR) = 2.30, 95% confidence interval (CI) = 1.20–4.42 for 25(OH)D <25.0 nmol/L and OR = 2.09, 95% CI = 1.22–3.58 for 25(OH)D 25.0–49.9 nmol/L) but not for 25(OH)D between 50.0 and 74.9 nmol/L (OR = 1.49, 95% CI = 0.85–2.62).
Conclusion: The higher-than-expected co-occurrence of low vitamin D levels and hyperglycemia (HbA1c ≥ 6.5%) are important public health concerns for older populations living in northern latitudes because both are common, and both have substantial adverse health consequences. Ensuring adequate vitamin D levels may help reverse the increasing trend in the development of diabetes mellitus and related complications in older people.

Introduction

Diabetes mellitus is a highly prevalent, long-term, metabolic condition in older adults. High glycoslyated hemoglobin (HbA1c) (hyperglycemia) is a risk factor in the development of diabetes mellitus (prediabetes), and recent evidence supports the use of HbA1c as a diagnostic test for diabetes mellitus.[1] New clinical practice recommendations from the American Diabetes Association (ADA) advocate the use of HbA1c in the diagnosis of diabetes mellitus rather than using the oral glucose tolerance test, largely on the basis of the established association between HbA1c and microvascular disease.[1] Vascular complications can result in disability, frequent hospital admissions, and institutionalization and is consistently found to be associated with poor general health. Low vitamin D levels have been shown in older people living in institutions and in the community[2,3] and can result in morbidity and frailty. The amount of sun exposure necessary to meet requirements depends on factors such as age, latitude, season, time of day, time of year, clothing, and skin pigmentation.[4] Older people are at higher risk of low vitamin D levels because of a decline in efficiency of vitamin D synthesis and lower renal conversion to its active form.[5] Dietary intake and supplement use can compensate for low endogenous production during winter months, but in the United Kingdom, dietary intake of vitamin D-containing foods (oily fish such as herring and mackerel, fortified margarines, meat and meat products, and eggs) in older people is also low.[6] In the United Kingdom, winter vitamin D levels in older people have been found to be associated with diet and overseas holidays within the past 6 months but not with winter sun exposure.[7]

There are plausible biological pathways for a role of low vitamin D levels in the pathogenesis of diabetes mellitus and control of blood glucose levels.[8] Low vitamin D levels predispose individuals to type 2 diabetes mellitus. Receptors for the activated form of vitamin D (1α,25-dihydroxyvitamin D3) have been identified in beta cells and immune cells.[9] Low vitamin D levels have been shown to impair insulin synthesis and secretion in humans.[10] There is evidence to suggest that vitamin D supplementation increases pancreatic insulin release and reduces insulin resistance[11] in people with impaired glucose tolerance[12,13] and type 2 diabetes mellitus.

The relationship between vitamin D levels and pathogenesis of diabetes mellitus is potentially of high public health importance because of the adverse effect of both states on well-being. In a nationally representative British survey of health in older people, the association between 25-hydroxy vitamin D (25(OH)D) levels and hyperglycemia was investigated, as well as the extent to which a variety of factors such as season of examination, social class, and general health status modified this association.

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