SUN-053 Gender Disparity In Association Between Serum Total Calcium And Blood Pressure In A Normocalcemic High Salt Diet Population.

Calcium metabolism has been shown to be associated with blood pressure, however, the results from gender subgroup analysis is conflicting. Some studies have shown strong correlation in women while other studies have shown weaker associations in women. Hence, the purpose of this epidemiology study is to evaluate the association of serum total calcium levels with blood pressure based on gender. This is a secondary analysis of epidemiology data from the Northeast China Rural Cardiovascular Health Study conducted 2012-2013. Resting blood pressure was measured 3 times in each participant using a standardized electric sphygmomanometer after sitting for 5 min. Men and non-pregnant women ≥18 years old, normocalcemic (2.25-2.58 mmol/L) [Diagnostics, 9th ed. People's Medical Publishing, China], and no prior history of hypertension or anti-hypertension medication were included. Serum calcium levels were stratified into quartiles (i.e., Q1: 2.25-2.33 mmol/L, Q2: 2.33-2.41, Q3: 2.41-2.50, Q4: 2.50-2.58 mmol/L), and hypertension was defined as mean systolic BP ≥140mmHg and/or mean diastolic BP ≥90mmHg. This study population has been previously shown to have high salt intake (9.7 g/d) [Li et al. J Am Soc Hypertens 9:358]. A total of 6550 normocalcemic participants met the inclusion criteria, of whom 51% were women and 39% were hypertensive. The mean serum calcium level was slightly higher in men than in women (2.38 ± 0.08 vs. 2.37 ±0.08; p=0.007) More men were hypertensive than women (42.6% vs. 35.1%; p<0.001). In the serum calcium quartiles, 34% (805/2401) normocalcemic participants in the lowest quartile Q1 were hypertensive, 38% (777/2037) in Q2, 44% (649/1470) in Q3, and 48% (310/642) in Q4. For men, the odds of hypertension increases as serum calcium quartile increases: the odds of hypertension in Q3 is 39% (95% CI, 1.151-1.673) higher compared to Q1, and in Q4 is 67% (95% CI, 1.321-2.160) higher. Similarly, in non-pregnant women, the odds of hypertension increases through the quartiles when compared to Q1: Q2 is 31% (95% CI, 1.095-1.556) higher, Q3 is 75% (1.448-2.121) higher, and Q4 is 99% (95% CI, 1.545-2.573) higher. Even though the odds of hypertension were consistently higher in women than in men in all serum calcium quartiles, there was no statistical difference in the odds ratio. In linear regression, the serum calcium level is a stronger predictor of systolic BP in women than in men (0.175 vs. 0.110; p=0.008), however the association with diastolic BP tends to be stronger in men than in women (0.070 vs. 0.063; p=0.74). In conclusion, in normocalcemic participants without a history of hypertension, the odds of having high blood pressure increases as serum calcium levels increases even within the normal range. In this high salt diet population, women trends to having higher odds of hypertension with a stronger association of systolic BP to serum total calcium levels.