Are Chinese people more prone to high blood pressure?

Hypertension (high blood pressure beyond current diagnostic threshold), is so common that each of us knows several family members and friends who carry this condition.  Hypertension is a leading cause to strokes and cardiovascular diseases.  Some of my Chinese friends believe that we Chinese are genetically prone to high blood pressure because we evolved with a diet rich in white rice and high-salt Chinese cuisine.  My father, who developed high blood pressure in his 60s, has been a strong believer of this theory too.

Why do we need two numbers in our blood pressure reading?

Many patients have asked me this question.  It is an important question, because to many of us, we prefer understanding the meaning of any numbers before we take them seriously and become willing to invest time taking care of them.  

Blood pressure in our arteries goes up and down like waves, and cycles along with the heat beats.  The 1st / higher number of the two is called systolic pressure.  In Greek “systole” means “drawing together, or contraction”.  As indicated by its name, a systolic pressure is the blood pressure when our heart contracts and pumps out blood into arteries, and the number we record is the highest point of blood pressure.  The 2nd / lower number, called diastolic pressure, is the blood pressure when our heart relaxes between beats and is the lowest point of the whole cycle.  The Greek word “diastole” means “drawing apart, or expansion”.

Which number in a blood pressure of 120/80 mmHg is more critical to us then?  A short answer is that both numbers are important for evaluating our health1.  There are debates among physicians and scientists over which number is better for predicting future risks for developing diseases in our heart and blood vessels.  The current consensus is that systolic pressure is of more predictive value for people over 50 and the diastolic pressure is more useful for people under 502.

Is high blood pressure more prevalent in the US or Chinese population?

There is indeed no simple answer to this question.  Studies on prevalence of hypertension include participants with different demographic characteristics and applied different diagnostic standards and research methods.  Therefore it is challenging to directly compare results from different studies.

Different diagnostic criteria for high blood pressure have been adopted by researcher conducting their studies.  Moreover, guidelines for normal blood pressure threshold change over time, as more data from research and clinical practice become available.  For instance, according to updated guidelines by American College of Cardiology/American Heart Association (ACC/AHA), blood pressure <120/80 mmHg is normal, and hypertension is diagnosed with systolic pressure >130 mmHg OR diastolic pressure >80 mmHg 3.  However, the current diagnostic criteria in China is different (systolic pressure >140 mmHg or diastolic pressure > 90 mmHg) 4.

Despite the difference between studies, we now have learned hypertension is very common in both populations, affecting at least 1 in 3 Chinese or Americans.  Two recent studies reported 28~30% of Chinese aged 18 years or older have blood pressure higher than 140/90 mmHg5,6.  In the US, 29% of Americans aged 18 years or older have high blood pressure according to the latest update from US National Center for Health Statistics7.  Another study in 2018 directly compared data from people aged 45-75 years old in two populations, ~ 12,000 Chinese and ~3,000 US residents, and showed that two populations have similar prevalence of hypertension8.  Hypertension is more prevalent as we age.  Notably, worldwide the prevalence has been increasing each year.

What about Chinese living in the US?

To control for many factors that make it difficult to compare blood pressure in various populations, some studies look at ethnic groups living in the same communities and showed that Chinese population living in the US have similar rate of hypertension to that of Caucasian Americans.  For instance, a study in 2004 on a population of over 6,000 people aged 45-85 in the US reported 39% of Chinese Americans have blood pressure over 140/90 mmHg, a rate similar to Caucasian whites and lower than African Americans and Hispanic participants9.  A more recent study investigated over 200,000 people in Northern California during 2011-2012 and drew a similar conclusion10.

However, we saw less awareness and less treatment

Studies showed that Chinese have lower awareness of hypertension and lower rate of treatment. Untreated and uncontrolled high blood pressure likely contribute to the higher incidence of strokes among Chinese8.  The insufficient awareness and treatment have been seen among both Chinese residing in China, and those living in the US.  This can be attributed to multiple factors.  For instance, Chinese Americans are found to have higher frequency of adverse effects such dry cough when taking ACE inhibitors such as lisinopril, one of the most commonly used blood pressure medication, and therefore are less likely to adhere to the medication11.  Chinese people are also more likely to use traditional herbal medication than modern antihypertensive medications.  The good news is that both awareness and treatment among Chinese have remarkably improved during recent years6.

Are there genetic factors that contribute specifically to high blood pressure in Chinese?

Blood pressure is controlled by complex physiological pathways related to heart, blood vessels, kidney and many other factors.  Conceivably hypertension is affected by many genetic factors instead a single gene.  Variations in over 100 genes have been associated with different susceptibility to hypertension.  Although some genetic factors, such as those regulating salt sensitivity and obesity, have been linked to susceptibility to hypertension in Chinese, more in-depth research is needed in order to fully understand the significance of such association12,13.

Summary

Hypertension in Chinese population, those who live in China and in the US, is no more prevalent than in other ethnic groups in the US.  Globally rate of hypertension is increasing.  It is critical to raise awareness among us in order to achieve effective prevention and treatment.

References

1.         Flint AC, Conell C, Ren X, et al. Effect of Systolic and Diastolic Blood Pressure on Cardiovascular Outcomes. N Engl J Med 2019;381(3):243–51.

2.         Kanegae H, Oikawa T, Okawara Y, Hoshide S, Kario K. Which blood pressure measurement, systolic or diastolic, better predicts future hypertension in normotensive young adults? J Clin Hypertens (Greenwich) 2017;19(6):603–10.

3.         Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension 2018;71(6):e13–115.

4.         Joint Committee for Guideline Revision. 2018 Chinese Guidelines for Prevention and Treatment of Hypertension-A report of the Revision Committee of Chinese Guidelines for Prevention and Treatment of Hypertension. J Geriatr Cardiol 2019;16(3):182–241.

5.         Lu J, Lu Y, Wang X, et al. Prevalence, awareness, treatment, and control of hypertension in China: data from 1·7 million adults in a population-based screening study (China PEACE Million Persons Project). The Lancet 2017;390(10112):2549–58.

6.         Wang Z, Chen Z, Zhang L, et al. Status of Hypertension in China: Results From the China Hypertension Survey, 2012-2015. Circulation 2018;137(22):2344–56.

7.         Fryar CD, Ostchega Y, Hales CM, Zhang G, Kruszon-Moran D. Hypertension Prevalence and Control Among Adults: United States, 2015-2016. NCHS Data Brief 2017;(289):1–8.

8.         Lu Y, Wang P, Zhou T, et al. Comparison of Prevalence, Awareness, Treatment, and Control of Cardiovascular Risk Factors in China and the United States. Journal of the American Heart Association [Internet] 2018 [cited 2019 Oct 19];Available from: https://www.ahajournals.org/doi/abs/10.1161/JAHA.117.007462

9.         Kramer H, Han C, Post W, et al. Racial/ethnic differences in hypertension and hypertension treatment and control in the multi-ethnic study of atherosclerosis (MESA). Am J Hypertens 2004;17(10):963–70.

10.       Zhao B, Jose PO, Pu J, et al. Racial/ethnic differences in hypertension prevalence, treatment, and control for outpatients in northern California 2010-2012. Am J Hypertens 2015;28(5):631–9.

11.       Hsu Y-H, Mao C-L, Wey M. Antihypertensive medication adherence among elderly Chinese Americans. J Transcult Nurs 2010;21(4):297–305.

12.       Kato N. Ethnic differences in genetic predisposition to hypertension. Hypertens Res 2012;35(6):574–81.

13.       Hoh B-P, Abdul Rahman T, Yusoff K. Natural selection and local adaptation of blood pressure regulation and their perspectives on precision medicine in hypertension. Hereditas 2019;156:1.

About the Author Isabel Wang, MD/PhD

I received my MD from PUMC in Beijing China and my Ph.D. in Biochemistry from Stony Brook University on Long Island. Over the years, I have worked in the fields of genetic research and clinical medicine in different parts of the US, including PA, MO, CT, FL, NY and MI. My research has been published in multiple scientific journals. Currently I live in Ann Arbor, MI with my husband and our children and Mango the orange tabby. I love hiking, running, baking, cooking and biking.

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