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Original article
The association between resting heart rate and type 2 diabetes and hypertension in Korean adults
  1. Dong-Il Kim1,2,
  2. Hyuk In Yang3,4,
  3. Ji-Hye Park3,4,
  4. Mi Kyung Lee3,4,
  5. Dong-Woo Kang5,
  6. Jey Sook Chae6,
  7. Jong Ho Lee7,
  8. Justin Y Jeon3,4,8
  1. 1Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts, USA
  2. 2Cardiovascular Research Laboratory, Spaulding Hospital Cambridge, Boston, Massachusetts, USA
  3. 3Exercise Medicine Center for Diabetes and Cancer Patients, Yonsei University, Seoul, Republic of Korea
  4. 4Department of Sport and Leisure Studies, Yonsei University, Seoul, Republic of Korea
  5. 5Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
  6. 6Research Center for Silver Science, Institute of Symbiotic Life-TECH, Yonsei University, Seoul, Republic of Korea
  7. 7Department of Food and Nutrition, College of Human Ecology Yonsei University, Seoul, Republic of Korea
  8. 8Cancer Prevention Center, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea
  1. Correspondence to Professor Jong Ho Lee, Department of Food and Nutrition, College of Human Ecology, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul 120-749, Republic of Korea; jhleeb{at}yonsei.ac.kr

Abstract

Objective The purpose of this study was to analyse the association between resting heart rate (RHR) and type 2 diabetes and hypertension in Korean adults.

Methods A total of 5124 participants, who participated in the exercise programme at the National Health Promotion Center between 2007 and 2010 (male=904, female=4220) were analysed in this study. Anthropometrics, body mass index (BMI), blood pressure (BP) and RHR were measured, and blood samples were collected after fasting for at least 12 hours.

Results To investigate the association between RHR and metabolic parameters, participants were divided into quartiles. Participants in the fourth quartile (RHR >80 beats per minute (bpm) showed significantly higher systolic and diastolic BP and glucose compared with participants in the first quartile (RHR <69 bpm). When logistic regression analyses were performed, participants in the fourth quartile of RHR had 2.76 times (95% CI 2.03 to 3.77; absolute risk (AR): 12.1% (166/1371)) higher odds of type 2 diabetes and 1.27 times (95% CI 1.04 to 1.55; AR: 22.2% (304/1371)) higher odds of hypertension compared with those in the first quartile of RHR (type 2 diabetes AR: 5.3% (71/1346); hypertension AR: 18.9% (254/1346)). Multiple regression analyses showed that both BMI and RHR were significantly associated with glucose and mean arterial pressure.

Conclusions RHR is significantly associated with type 2 diabetes and hypertension independent of age, gender, BMI, smoking, drinking and family history of disease. RHR in combination with BMI, and multiple linear regression analyses emphasise the importance of the association of RHR with type 2 diabetes and hypertension in Korean adults.

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Introduction

Since the publication of the first study examining the association between resting heart rate (RHR) and mortality from cardiovascular and non-cardiovascular causes in 1980,1 there has been emerging evidence suggesting that RHR is associated with cardiovascular mortality in the general population2 ,3 as well as in people with known diseases such as chronic kidney disease,4 hypertension,5 cardiac events,6 and vascular disease.7 ,8 It has been estimated that an increase in RHR by 10 beats per minute (bpm) is associated with a 20% increase in the risk of cardiac death.9 In another study, an increase in home-measured RHR by 5 bpm was associated with a 17% increase in 10-year cardiovascular mortality.2

Due to its simplicity to measure and cost-effectiveness, RHR is an attractive tool in assessing the prevalence of diseases such as metabolic syndrome,10 type 2 diabetes11 ,12 and cardiovascular disease.13 ,14 Rogowski et al10 performed a cross-sectional study in a sample of 7706 individuals (5106 men and 2600 women) and found that individuals in the highest quintile of RHR (>80 bpm in men and >82 bpm in women) had a 4.1 and 4.2 times higher prevalence of metabolic syndrome, respectively, compared with individuals in the lowest quintile of RHR (<60 bpm in men and <64 bpm in women). Grantham et al11 studied a total of 5817 participants (221 of whom developed diabetes) and found that participants with a RHR of >80 bpm were 1.89 times more likely to develop diabetes over 5 years compared with participants with a RHR <60 bpm. Hsia et al3 have shown that RHR independently predicts myocardial infarctions and coronary deaths in women. They also found that RHR was more strongly associated with coronary events in participants whose age was between 50 and 64 years compared with those whose age was between 65 and 79 years.3

Although studies have clearly demonstrated the usefulness of RHR in predicting the risk of mortality as well as the prevalence of metabolic diseases, the combined impact of RHR with other known predictors for metabolic has not been fully elucidated. In a previous study, Nagaya et al12 examined the combined impact of RHR and blood pressure (BP) on the risk of type 2 diabetes and found that male and female participants with higher RHR and higher BP had a 2.25 and a 2.58 times higher risk, respectively, of the incidence of type 2 diabetes as compared with those with lower RHR and lower BP.

Similarly, the body mass index (BMI) is a known contributor of type 2 diabetes and hypertension. Therefore, one can speculate that compared with those who have lower RHR and lower BMI, those with higher RHR and higher BMI would have a higher prevalence of type 2 diabetes and high BP. Therefore, the purpose of our study was to examine the independent and combined association of RHR and BMI with type 2 diabetes and hypertension in the Korean adult population at risk of type 2 diabetes and hypertension.

Methods

Study population

We analysed the data of 5124 participants from the National Health Insurance Corporation (NHIC) biennial examinations who participated in an exercise programme at the National Health Promotion Center (NHPC) between 2007 and 2010. Patients whom it was deemed too dangerous to participate, either due to treatment or prior health conditions, were excluded from this study. The NHIC examination includes BMI, RHR, BP, serum glucose and total cholesterol (TC) measurements. If more than one of the following variables were abnormal, participants qualified for the use of the NHPC for 3–6 months: BMI >30 kg/m2, systolic blood pressure (SBP) >140 mm Hg, diastolic blood pressure (DBP) >90 mm Hg, fasting glucose >126 mg/dL, TC >230 mg/dL, high-density lipoprotein-cholesterol <40 mg/dL, low-density lipoprotein-cholesterol >150 mg/dL, triglyceride >200 mg/dL, aspartate aminotransferase >51 IU/L and alanine aminotransferase >46 IU/L. The NHIC biennial examinations were performed by trained healthcare professionals who followed the standard procedure. RHR and BP were measured after a 10 min rest in the seated position with a digital BP monitor (Helmas-SH-9600B, Seoul, Republic of Korea). Blood samples were collected after a 12-hour fast. Participants were also asked to fill out questionnaires that assessed their lifestyle behaviours, such as smoking and alcohol consumption, and medical history. Written informed consent was obtained from all participants before assessment. The characteristics of the participants are shown in table 1.

Table 1

Participant's characteristics

Type 2 diabetes and hypertension

The diagnostic criteria for type 2 diabetes were one of the following: fasting glucose ≥126 mg/dL (7.0 mmol/L) or the current use of antidiabetic medication. Likewise, the criteria for hypertension were one of the following: SBP ≥140 mm Hg, DBP ≥90 mm Hg or the current use of antihypertensive medication.

Statistical analysis

Statistical analysis was performed using SPSS, Windows V.18.0 (SPSS, Chicago, IL, USA). Prior to statistical analysis, all participants on medication known to effect heart rate were excluded from statistical analysis. Participant's characteristics are presented according to RHR quartiles: <69 bpm, 69–74 bpm, 75–80 bpm, >80 bpm. Analysis of covariance was used to determine the group differences in BP, glucose and TC parameters adjusted for age, gender, BMI, smoking, drinking, family history of diabetes and hypertension. Age and BMI were continuous variables, and gender (male or female), smoking (current smoker or not a smoker), alcohol (currently drinks alcohol, does not drink alcohol) and family history of diabetes and hypertension (yes or no) were categorical variables. A logistic regression analysis (odds ratio (OR) with 95% CI) was used to assess the association of RHR quartiles with type 2 diabetes and hypertension, after adjustment for age, gender, BMI, smoking, drinking, family history of diabetes and hypertension. An additional logistic regression analysis was conducted that combined the primary dependable variable, RHR, with BMI, another variable correlated with type 2 diabetes and hypertension, to form four groups: low BMI (<25 kg/m2) and low RHR (≤80 bpm), low BMI and high RHR (>80 bpm), high BMI (≥25 kg/m2) and low RHR, high BMI and high RHR. The WHO Asian BMI standard for obesity, ≥25 kg/m2,15 and a RHR cutoff of 80 bpm, which has often been used in previous studies,16–18 was used for this analysis, with adjustments made for age, gender, smoking, drinking and family history of diabetes and hypertension. Finally, a multiple regression analysis was performed to determine the association of fasting glucose and mean arterial pressure (MAP) with other related variables. Since Kolmogorov-Smirnov test showed that age, BMI and RHR were non-normally distributed, these variables were log transformed before analysis. Statistical significance was set at p<0.05.

Results

The clinical characteristics of the participants are reported in table 1. When participants were divided into RHR quartiles, participants with higher RHR had significantly higher BP and glucose even after adjusting for age, gender, BMI, smoking, alcohol consumption and family history of diabetes and hypertension (table 2).

Table 2

Blood variables according to resting heart rate quartiles

When the ORs were calculated and compared with those in the first quartile (absolute risk (AR): 5.3% (71/1346)), participants in the second (1.71, 95% CI 1.22 to 2.39; AR: 7.7% (96/1242)), third (2.03, 95% CI 1.46 to 2.83; AR: 9.4% (109/1165)) and fourth quartile (2.76, 95% CI 2.03 to 3.77; AR: 12.1% (166/1371)) had significantly higher odds of type 2 diabetes even after adjusting for age, gender, BMI, smoking, drinking and a family history of diabetes. The risk of having hypertension was only significantly increased in those in the fourth quartile (1.27, 95% CI 1.04 to 1.55; AR: 22.2% (304/1371)) compared with those in the first quartile (AR: 18.9% (254/1346)) (table 3).

Table 3

OR according to the quartile of resting heart rate

To study the combined impact of obesity and RHR, participants were divided into four groups: low BMI and low RHR, high BMI and low RHR, high BMI and low RHR and high BMI and high RHR. Our analyses showed that the participants in the high BMI and high RHR group had significantly higher odds of type 2 diabetes (1.91, 95% CI 1.40 to 2.62; AR: 12.3% (86/699)) and hypertension (1.43, 95% CI 1.14 to 1.80; AR: 22.3% (156/699)) when compared with the low BMI and low RHR group (type 2 diabetes AR: 6.7% (127/1887); hypertension AR: 16.5% (312/1887)), after multivariable adjustment. Subjects who were in the low BMI and high RHR group had significantly higher odds of type 2 diabetes (1.92, 95% CI 1.40 to 2.62; AR: 11.9% (80/672)) and hypertension (1.47, 95% CI 1.17 to 1.86; AR: 22.0% (148/672)), compared with subjects who were in the low BMI and low RHR group after adjustments for age, gender, BMI, smoking, drinking and family history of disease. On the other hand, subjects who were in the high BMI and low RHR group had significantly higher odds of hypertension (1.31, 95% CI 1.10 to 1.56; AR: 21.0% (392/1866)), but not type 2 diabetes, compared with subjects who were in the low BMI and low RHR group after the same adjustments (table 4).

Table 4

OR according to BMI and RHR

To further understand the combined impact of BMI and RHR on the prevalence of type 2 diabetes and hypertension, multiple regression analyses were performed. The analyses showed that both BMI and RHR were significant contributing factors for glucose and MAP (table 5).

Table 5

Multiple linear regression analysis to assess the association of fasting glucose and MAP with RHR and BMI

Discussion

We investigated the associations of RHR with type 2 diabetes and hypertension in Korean adults. The present study demonstrated that higher RHR is associated with increased odds of type 2 diabetes and hypertension. These significant associations were independent of age, gender, BMI, smoking, drinking and family history of diabetes and hypertension. Both RHR and BMI were significant contributing factors for the prevalence of type 2 diabetes and hypertension.

Analysis of the associations between RHR and hypertension, showed that participants whose RHR was >80 bpm had 1.27 times higher odds of hypertension compared with participants whose RHR was <69 bpm after adjusting for age, gender, BMI, smoking, drinking and family history of hypertension. This is consistent with previous research,3 which reported that the risk of hypertension significantly increased over 11% in the highest quintile (>76 bpm) of RHR, compared with the lowest quintile (≤62 bpm) of RHR. Other studies have reported that increased RHR was associated with an increased risk of coronary heart disease19 along with its prognosis,20 and an increased risk for vascular mortality in vascular patients7 and male industrial employees.21 Further analyses were performed in our study, investigating the combined association of BMI and RHR on the prevalence of hypertension, by dividing the participants into four groups. Participants with higher BMI showed higher odds of hypertension than participants with lower BMI, compared with the respective RHR group. However, participants with a BMI of <25 kg/m2 and RHR >80 bpm showed higher odds of hypertension than participants with a BMI of ≥25 kg/m2 and RHR of ≤80 bpm. Moreover, a multiple regression analyses found both RHR and BMI to be significant contributing factors of MAP. Our study confirms that high RHR is a good indicator for the increased risk of hypertension in Korean adults.

In our study, we observed that participants with RHR >80 bpm had 2.76 higher odds of type 2 diabetes compared with participants with RHR <69 bpm. This increased risk of type 2 diabetes among participants with high RHR was independent of BMI. Further analyses were conducted to understand the combined impact of BMI and RHR on the odds of type 2 diabetes, dividing the participants into four groups. Generally, higher BMI is associated with higher odds of type 2 diabetes, but that trend was not observed in our study. We did not observe higher odds of type 2 diabetes among participants whose BMI was ≥25 kg/m2 if their RHR was ≤80 bpm. On the other hand, we observed 1.91 higher odds of type 2 diabetes among participants whose BMI was ≥25 kg/m2 and their RHR was >80 bpm. Likewise, we observed a 1.92 times higher prevalence of type 2 diabetes among participants whose BMI was <25 kg/m2 and their RHR was >80 bpm. A multiple regression analyses found both RHR and BMI to be significant contributing factors of fasting glucose.

Previous studies have also reported that RHR is associated with the risk of hypertension and diabetes.3 ,19 ,22 ,23 Furthermore, previous studies have also indicated that higher RHR increases the relative risk of all-cause mortality and cardiovascular mortality.7 ,21 ,24 Therefore, RHR is a great tool to assess the risk of disease and mortality, as well as serve as an index for autonomic function.25 Additionally, given the effects of exercise on RHR and autonomic control,26 ,27 the significant association of RHR with the prevalence of type 2 diabetes and hypertension may also be explained by the patients' levels of fitness. The beneficial effects of exercise and higher level of fitness on insulin resistance and BP, and the prevention of type 2 diabetes and hypertension have been consistently reported.28 ,29 Therefore, it is not surprising to observe that higher RHR, which may reflect lower levels of fitness, was associated with a higher risk of type 2 diabetes and hypertension. Higher RHR could also be due to autonomic neuropathy (ie, vagal impairment) in diabetic patients and therefore caution needs to be practiced in assuming higher RHR simply reflect lower level of fitness. In our study, we confirmed that higher RHR was a good indicator for the increased risk of type 2 diabetes in Korean adults, independent of BMI, highlighting the importance of RHR.

The limitations of this study include the lack of data regarding the participants' lifestyles, such as nutrition, medication, physical activity and exercise that are associated with the development of type 2 diabetes and hypertension. Second, although an association of RHR with type 2 diabetes and hypertension can clearly be seen in this study, due to the cross-sectional design, it is difficult to draw any causal inference from this study.

Our study suggests that among Korean adults, RHR is independently associated with type 2 diabetes and hypertension. By using a variety of statistical analyses, this study emphasises the association and importance of RHR with the prevalence of type 2 diabetes and hypertension.

Key messages

What is already known on this subject?

  • Resting heart rate (RHR) is associated with a wide range of chronic diseases, various conditions and all-cause/cause specific mortality in various population groups. It has even been shown to be associated with the prognosis of some diseases.

What might this study add?

  • Logistic regression analyses showed that participants in the fourth quartile of RHR (highest) had 2.76 (95% CI 2.03 to 3.77, absolute risk (AR): 12.1% (166/1371)) higher odds of type 2 diabetes and a 1.27 (95% CI 1.04 to 1.55; AR: 22.2% (304/1371)) times higher odds of hypertension compared with those in the first quartile of RHR. Using a cross-stratification method, we further found that compared with participants with a low body mass index (BMI) (<25 kg/m2) and low RHR (<80 beats per minute (bpm)), participants with a high BMI (≥25 kg/m2) and high RHR (≥80 bpm) were 1.91 (95% CI 1.40 to 2.62; AR: 12.3% (86/699)) and 1.43 (95% CI 1.14 to 1.80; AR: 22.3% (156/699)) times more likely to have type 2 diabetes and hypertension, respectively. Multiple regression analyses showed that both BMI and RHR were significantly associated with glucose and mean arterial pressure.

How might this impact on clinical practice?

  • This study provides a possible use of RHR as a method to identify a high-risk population within what is considered a high-risk population (BMI ≥25 kg/m2), and what would be considered low-risk population (BMI <25 kg/m2).

Acknowledgments

This work was supported by the Bio-Synergy Research Project (NRF-2012M3A9C4048762) of the Ministry of Science, ICT and Future Planning through the National Research Foundation, Republic of Korea, & the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea (NRF-2015S1A5B8036349).

References

Footnotes

  • Contributors All authors analysed data, developed the study protocol and design and read, commented on, contributed to and approved the submitted manuscript. D-IK, HIY and JYJ were the main contributors to the writing of the manuscript. J-HP, MKL, D-WK and JSC contributed to the planning and interpretation of the study. As the corresponding authors and guarantors, JHL and JYJ are responsible for the overall content of this manuscript.

  • Competing interests None declared.

  • Ethics approval Ministry of Health and Welfare, Government of Korea.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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