College of Public Health, ETSU The relationship between Calcium Intake and Hypertension among Obese Adults in the U.S. College of Public Health, ETSU Yang Chen, MS Shimin Zheng, PhD Liang Wang, MD, DrPH 4/4/2013

Contents Introduction 1 Methods 2 Results 3 Discussion 4 Conclusion 5

Introduction Hypertension – 1 in 3 U.S. adults (estimated 68 million) Increases the risk for heart disease and stroke leading causes of death in the United States. Obesity – risk factor for hypertension Incidence of hypertension is high among obese people Calcium intake – dietary risk factor for hypertension

Introduction Cross-sectional study Study design Cross-sectional study Study objective Examine the relationship between the calcium intake and hypertension among obese adults in U.S. during 1999 to thru 2010

Methods – Study population Participants of National Health and Nutrition Examination Study (NHANES) from 1999 and 2010. Included criteria Inclusion criteria: Adult (age≥20 years) Obesity Generalized obesity – body mass index(BMI) ≥30 kg/m2 Central obesity – waist circumference ≥102 cm for men and ≥88 cm for women No pregnancy

Methods – Variable measurement Outcome Risk Factor Exposure Outcome Covariates Calcium intake Hypertension Elevated systolic blood pressure (SBP ≥ 140 mmHg) Elevated diastolic blood pressure (DBP ≥ 90 mmHg) Demography– age, gender, race, education, poverty Behavior – smoking, alcohol use Condition – diabetes Unit: mg/d 24-hour dietary interview

Methods – Statistical Analysis Sample – stratify by quartiles of calcium intake. Descriptive Analysis of variance (ANOVA) tests Chi-square test Regression Simple logistic regression models Multiple logistic regression models SAS (version 9.0; SAS Institute Inc, Cary, NC)

Results Fig. 1 Prevalence of hypertension, elevated SBP and DBP among obese adults by calcium intake quartiles in the U.S. (1999–2010) The color used for bars are too close

Results Table 2. Simple and Multiple logistic regression analysis of hypertension by calcium intake quartiles and other predictors among adults with obesity in the U.S. (1999–2010)

Results Table 3. Simple and Multiple logistic regression analysis of hypertension, elevated SBP and DBP by calcium intake quartiles among adults with obesity in the U.S. (1999–2010)

Discussion Increasing calcium intake, decreasing probability of hypertension among obese adults. The probability of hypertension among obese adults can decreased by increasing calcium intake. Inverse relationship between blood pressure status and dietary calcium intake. The protective effect of calcium on blood pressure can be partly explained by the influence of calcitriol on [Ca2+]i. An increase of [Ca2+]i in vascular smooth muscle cells can result in vasoconstriction and a consequent rise in blood pressure.

Discussion Strengths Limitations Large scale – national wide, 12 years Focus on obese adults Adjusted Other covariates adjusted. Cross-sectional study Physiological mechanism

Conclusion Inadequate calcium intake may increase the risk of hypertension, high SBP, or high BDP among obese adults. Hypertension Calcium intake Obesity Increasing the calcium intake in obese adults can be considered as a strategy to prevent hypertension. Further studies are needed to understand physiological mechanism.

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