High or Low Calcium Intake Increases Cardiovascular Disease Risks in Older Patients With Type 2 Diabetes

Jui-Hua Huang; Leih-Ching Tsai; Yu-Chen Chang; Fu-Chou Cheng

Disclosures

Cardiovasc Diabetol. 2014;13(120) 

In This Article

Methods

Study Design

The investigation employed a cross-sectional research design targeting patients with type 2 diabetes aged 65 years and above. Diabetes was diagnosed in the Endocrine and Metabolism Clinic according to the guidelines of the American Diabetes Association (ADA-1997).[31] The inclusion criteria for patients were as follows: 1) type 2 diabetes for >6 months; 2) no change in any medications for the past 3 months; 3) stable lifestyle for the past 3 months; and 4) absence of heart failure, cirrhosis, current malignancy, chronic renal failure, or clinically relevant infection (CRP levels > 10 mg/L). Patients with signs of serious deterioration in comprehension and memory were excluded. A total of 197 patients were included in the study. This investigation was performed in compliance with the Helsinki Declaration, and approved by the Changhua Christian Hospital Institutional Review Board (CCHIRB: 090419).

Assessment of Dietary Intakes, Lifestyle, and Body Mass Index

Dietary intakes were assessed using 24-h recall and 7-day typical dietary intake by interview and dietary records.[32,33] During the interview, quantitative tools including standard measuring spoons and cups, food models, food pictures and photos, as well as traditional household bowls, cups, and spoons were used to help the elderly subjects properly estimate their dietary intake.[34] Intakes of Ca, Mg, and other nutrients were analyzed using Taiwan's Nutrition Database and the EKitchen nutritional analysis software (Nutritional Chamberlain Line, Professional Edition, version 2001/2003, EKitchen Inc, Taichung, Taiwan).[35] In addition, data on potential confounders, such as lifestyle factors, including physical activity, smoking, and alcohol consumption, were collected using a self-reported questionnaire. Anthropometric measurements included height and weight. Body mass index (BMI) was calculated as weight (kg)/height (m2).

Moderate nutrient intakes were defined as consumption of 67% of RDA for that nutrient or 67% of its adequate intake value (AI).[36] In the present study, assessment of Ca intakes was based on a previous RDA for Ca for Taiwanese aged 65 years and above (600 mg/day), because the Ca intake level for majority of older patients with diabetes was below the current AI for Ca (1000 mg/day). The Ca intakes were categorized as follows: 1) low: Ca intakes <67% of RDA for Ca; 2) moderate: Ca intakes approximately 67%–100% of RDA for Ca; and 3) high: Ca intakes more than RDA for Ca.[36] In addition, assessment of Mg intakes was based on RDA for Mg for Taiwanese aged 65 years and above (350–360 mg/day for older men and 300–310 mg/day for older women). The Mg intakes were categorized as follows: 1) low: Mg intakes <67% of RDA for Mg, 2) moderate: Mg intakes approximately 67%–100% of RDA for Mg, and 3) high: Mg intakes more than RDA for Mg.[36]

Markers of Inflammation and CVD Risks

Inflammatory markers were measured by the hospital medical laboratory (certified ISO15189) to assess CVD risk and included high-sensitivity CRP,[37] leukocyte counts,[38] platelet counts,[39] and red blood cell distribution width (RDW).[40] The high-sensitivity CRP (CV <3.0%) was measured by particle-enhanced turbidimetric immunoassay (Dimension, Siemens, Newark, USA). The CRP levels of <1, 1–3, and >3 mg/L represented low, moderate, and high CVD risk, respectively.[37] Patients with clinically relevant infection (CRP levels >10 mg/L) were excluded. In addition, blood leukocytes (CV <3.0%) and platelets (CV <3.0%) were measured by the direct current detection method (XT1800i, Sysmex, Kobe-shi, Hyogo, Japan) and RDW was calculated. The subjects were stratified into tertiles (low, medium, and high) based on leukocyte counts, platelets, and RDW.

Renal Functional Measurements

The serum creatinine levels (CV <2%) were determined by the alkaline picrate-kinetic method. The estimated glomerular filtration rate (GFR) was calculated as eGFR (mL/min/1.73 m2) (Simplified Modification of Diet in Renal Disease (MDRD)) = 186 × serum creatinine−1.154 × Age−0.203 for men and 186 × serum creatinine−1.154 × Age−0.203 × 0.742 for women, according to the formula recommended by the Taiwan Society of Nephrology.[41]

Statistical Analysis

The categorical variables were analyzed by the chi-square test, and the data are presented in number (n) and percent (%). For continuous dependent variables, comparisons of the means were analyzed by 2-tailed t-test (2 groups) or one-way ANOVA followed by Scheffe's multiple comparisons test, and the data are presented as mean ± SD. In addition, the correlations of dietary Ca and/or Mg intakes and markers of inflammation with CVD risks were examined by multivariate analyses, followed by Bonferroni's multiple comparisons test, and the data are presented as adjusted mean ± standard error (SE). All the statistical procedures were performed using SPSS 17.0 statistical software (SPSS Inc., Chicago, IL, USA), and a p value <0.05 was considered statistically significant.

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