The Benets of Physical Activity on Indicators of Cardiovascular Risk in Community-Dwelling Older Adults with Hypertension in Korea: A Longitudinal Study

Purpose: The study aimed to explore the effects of physical activity on indicators for cardiovascular risk in a sample of community-dwelling older adults with hypertension. Methods: This longitudinal study used data collected from the Elderly Cohort Database of the National Health Insurance Service in South Korea between 2002 and 2013. Participants included 10,588 older adults ( ≥ 60 years) with hypertension. Data assessing self-reported physical activity, blood pressure, fasting blood glucose, body mass index, and total cholesterol levels throughout the 12-year study were extracted from the original database and analyzed. Participants were categorized into 4 groups based on the reported changes in physical activity over time; Group I (totally inactive), II (inactive to active), III (active to inactive), and IV (totally active). Cox proportional hazard model was used to conrm the risk of cardiovascular indicators over time in each group. Results: Participants’ mean age was 64.2 years in the initial year of 2002. The number of participants in Groups I, II, III, and IV was 4032, 2697, 1919, and 1940, respectively. Group IV showed a signicant decline in risk for uncontrolled hypertension compared to Group I (HR = 0.87, 95% CI [0.800-0.948]). Group II showed a signicant decrease in risk for uncontrolled diabetes compared to Group I (HR = 0.94, 95% CI [0.888-0.999]). Conclusions: Physical activity is an essential non-pharmacological and self-management intervention that can be easily implemented among older adults with hypertension. Healthcare providers should be aware of the importance of older adults’ physical activity and encourage them to perform and maintain it steadily for better long-term cardio-metabolic outcomes. glucose level and from normal to high for BMI and total cholesterol level. The signicance of the analyzed curves was tested using the log-rank test. A Cox proportional hazard model was also used to conrm the risk of cardiovascular indicators over time in each group. on CVD indicators over a period of 12 years in a sample of older adults with hypertension living in the community. Physical activity is one of the most important non-pharmacological and self-management interventions that can be easily implemented with older adults with hypertension in the community. Our ndings indicate that continuous participation in physical activity can signicantly lower the long-term CVD indicators in older adults. Healthcare providers should be aware of the importance of physical activity for older adults and encourage them to engage in and maintain it consistently for improved long-term cardio-metabolic outcomes.


Introduction
The population of older adults is expected to grow from 900 million, representing approximately 12% of the world's population, in 2015 to 2 billion, approximately 22% of the world's population, in 2050 worldwide [1]. South Korea is one of the rapidly becoming aging societies. In 1980, the number of older adults accounted for only 3.8% of South Korea's population, but in 2019, it reached 15.7%, with the percentage expected to rise to 33.9% in 2040 and 46.5% in 2067 [2]. Consistent with the increase in the older population, the prevalence of chronic diseases has risen. A 2008 survey of older adults reported that the average number of chronic diseases in this population was 2.1 [3], which increased to 2.7 in 2017 [4]. In particular, the prevalence of hypertension in older adults had increased to 59% in 2017, indicating that over half of older adults in Korea have high blood pressure (BP) [4].
Hypertension is the most common chronic disease among adults and older people, with 1.13 billion worldwide, and is considered the most common and powerful risk factor for developing cardiovascular disease (CVD) [5,6]. CVD is the leading cause of death globally, accounting for 31% of deaths worldwide in 2016 [7]. The risk factors for CVD include increased age, smoking, alcohol consumption, obesity, hypertension, diabetes, dyslipidemia, and sedentary lifestyle [8,9].
Physical activity is considered as an essential recommendation for BP control in patients with hypertension in many studies, and its importance was supported in a meta-analysis of 27 interventions with patients diagnosed with hypertension [10,11]. For example, one intervention reported that physical activity (i.e., aerobic training) in 52 postmenopausal women with hypertension (mean age of 64 years) signi cantly decreased systolic BP over 12 weeks [12].
Another study compared the cardiovascular risks of men with hypertension who played 1 hour of soccer twice a week and men who did not, showing that systolic and diastolic BPs in soccer group decreased by 12mmHg and 8mmHg, respectively, over 6 months [13].
However, few studies have reported the longitudinal effects of physical activity in older people with hypertension on their overall CVD risk factors, such as diabetes, dyslipidemia, and obesity. For physically independent older adults in the community, measuring daily physical activity rather than the amount of short-term exercise during their participation in an intervention program is important [14]. Furthermore, most studies of community-based physical activity intervention have yet to explore long-term effects that extend beyond a year [11]. Therefore, this study's objective was to explore the long-term effects of physical activity on CVD indicators in community-dwelling hypertensive older adults.

Study design and participants
A secondary data analysis of a prospective longitudinal study was conducted using the Elderly Cohort Data of the National Health Insurance Service in South Korea between 2002 and 2013. This representative survey in Korea was originally designed to analyze the risk factors and prognosis of senile diseases and included socioeconomic information, hospital-use history, and diverse health examination results.
The participants in this study were 10,588 older adults (over 60 years of age) with hypertension. This Elderly Cohort Data surveyed the number of days of physical activity per week in 2002-2008, and the number of days participants engaged in intense, moderate, and walking activity per week in 2009-2015.
Therefore, we identi ed physical activity as "yes" or "no", regardless of its time and intensity. Participants were categorized into 4 groups by their changes in physical activity presence or not over time. Group I included the people who reported that they did not engage in physical activity in their daily life throughout the assessment period of 2002-2013 (the totally inactive group). Group II included those who did not engage in physical activity in 2002 but began to participate in physical activity by 2013 (the inactive to active group). Group III included those who reported that they were physically active in 2002 but did not sustain their participation in physical activity when assessed in 2013 (the active to inactive group). Finally, Group IV included those who reported remaining physically active throughout 2002-2013 (the totally active group).
Variables BP was measured as systolic/diastolic pressure (mmHg) on the participants. According to the European Society of Hypertension, BP over 160/100mmHg is considered Stage 2 (more severe) hypertension [15]; therefore, BP measurements that were 160/100mmHg or higher were used as the criteria of uncontrolled BP in this study.

Blood glucose
In the cohort survey, pre-meal plasma glucose was checked in 2002-2010, and fasting plasma glucose was measured in 2011-2013. Blood glucose was considered to be controlled if it was less than 100mg/dL [16], so blood glucose greater than 100mg/dL was categorized as uncontrolled glucose in this study.

Body mass index
Height (cm) and weigh (kg) were measured on the participants. BMI was calculated from the data and was categorized as being normal or obese using the cut-off value of 25kg/m 2 [17].

Total cholesterol
Total cholesterol level was measured for the participants. Participants were categorized as normal or having hypercholesterolemia using the cut-off value of 200mg/dL [9].

Covariates
Age, gender, and economic status were identi ed as demographic characteristics. Economic status was divided into 4 groups: Low, Lower-Middle, Upper-Middle, and High. Smoking and alcohol consumption were included as characteristics of participants' health behaviors. The number of comorbidities and family history of related diseases (i.e., hypertension, diabetes, heart disease, and cerebral disease) were included as disease-related characteristics.

Data analyses
Data cleaning and analysis was performed using SPSS version 23.0 (IBM SPSS Statistics, Armonk, NY). Demographic characteristics, health behaviors, and disease-related characteristics in 2002 were reported using descriptive statistics, such as frequency (percentage) and mean (standard deviation). Chi-square tests and one-way ANOVA were used to analyze differences among the physical activity groups. In addition, the Kaplan-Meier method was used to analyze the time to change from controlled to uncontrolled for BP and glucose level and from normal to high for BMI and total cholesterol level. The signi cance of the analyzed curves was tested using the log-rank test. A Cox proportional hazard model was also used to con rm the risk of cardiovascular indicators over time in each group.

Ethical considerations
This study was approved by the institutional review board of XX University (IRB No. AJIRB-SBR-EXP-19-127). After receiving approval, a request was made to access the Elderly Cohort Data to the National Health Insurance Data Sharing Services. All data were de-identi ed before conducting the analysis, so personal identi cation was protected.

Results
General characteristics among physical activity groups at baseline At baseline in 2002, the mean ages of Group I (the totally inactive group), II (the inactive to active group), III (the active to inactive group), and IV (the totally active group) were 64.58, 64.05, 64.13, and 63.67 years, respectively. Group IV was signi cantly younger than the other three groups (F = 24.43, p < .001).
The mean number of comorbidities ranged from 0.20 to 0.24 across the 4 groups, and individuals in Group III and IV had signi cantly more diseases (F = 3.99, p = .008). Further, the prevalence of family history of hypertension (χ 2 = 42.87, p < .001), diabetes (χ 2 = 32.37, p < .001), heart disease (χ 2 = 19.65, p < .001), and cerebral disease (χ 2 = 43.95, p < .001) were signi cantly higher for those in Group III and IV than those in Group I and II (Table 1). Comparison of cardiovascular indicators among physical activity groups at baseline and after 12 years No signi cant differences were found in the rates of uncontrolled systolic BP (19.7-22.2%) across 4 groups at baseline; however, the rates of uncontrolled systolic BP were signi cantly different between the groups after 12 years (χ 2 = 17.07, p < .001). Group IV had the lowest rate (4.6%) of uncontrolled systolic BP, and Group I had the highest (7.1%). There were no signi cant differences in the rates of uncontrolled diastolic BP (19.3-20.0%) across the 4 groups at baseline; however, the rates of uncontrolled diastolic BP were signi cantly different across the groups after 12 years (χ 2 = 10.89, p = .012). Group IV had the lowest rate (2.6%) of uncontrolled diastolic BP, and Group I had the highest (3.9%).
Regarding BMI, there were also signi cant differences among the 4 groups at baseline (χ 2 = 11.61, p = .009) and after 12 years (χ 2 = 16.57, p < .001). BMI was signi cantly higher in Group III and IV than in Group I and II at baseline and after 12 years.
Regarding total cholesterol level, no signi cant differences in the rates of hypercholesterolemia (53.0-55.4%) among 4 groups at baseline were found; however, the rates of hypercholesterolemia signi cantly differed among the groups after 12 years (χ 2 = 19.05, p < .001). Group IV had the lowest rate (30.0%) of hypercholesterolemia, and Group I had the highest (35.5%; Table 2).

Bene ts of physical activity on cardiovascular indicators
We examined the longitudinal effects of physical activity on BP, glucose, BMI, and total cholesterol levels of the participants using the Kaplan-Meier analysis (Figs. 1 & 2). The length of time for changing from controlled to uncontrolled BP and glucose was signi cantly different among the 4 groups. Speci cally, the length of time for changing to uncontrolled BP was signi cantly longer in Group IV than in Group I (7.72 years; χ 2 = 16.56, p = .001), and the length of time to change to uncontrolled glucose was signi cantly longer in Group II than in Group I (χ 2 = 15.77, p = .001).
As the results of the Cox proportional hazard model (Table 3), after adjusting for the covariates (i.e., age, gender, economic status, smoking, alcohol consumption, number of comorbidities, and family history), those in Group IV had 12.9% lower risk of having uncontrolled BP than those in Group I (HR = 0.871, 95% CI [0.800-0.948]). In addition, those in Group II had 5.8% lower risk of having uncontrolled glucose than those in Group I (HR = 0.942, 95% CI [0.888-0.999]).

Discussion
This secondary data analysis of a prospective longitudinal study examined the bene ts of physical activity over 12 years on the cardiovascular risk factors in a sample of older adults with hypertension living in the community. Our results demonstrated that the group with consistent and more strenuous physical activity had a signi cantly lower risk of having uncontrolled BP than the group who did not engage in any speci c physical activity over 12 years. In addition, the group whose physical activity level changed from inactive to active showed a lower risk of having uncontrolled glucose levels than the group that did not engage in any physical activity over 12 years.
These results support previous research indicating that regular physical activity can lower BP and blood glucose and reduce CVD risks [11,[18][19][20]. Oxygen, supplied to the body during physical activity, strengthens the muscles of the cardiovascular system and is effective in improving peripheral vascular resistance associated with CVD indicators, such as hypertension and diabetes [21]. A recent study examined the effects of physical activity on CVD and mortality that used data from 17 countries and 130,843 people and concluded that all types of physical activity could be effective in reducing CVD risks and overall mortality [22].
The characteristic feature of a long-term hypertensive heart is a compensatory increase in left ventricular wall thickness (hypertrophy) that is also considered to be an independent predictor of uncontrolled hypertension [19]. If this condition persists, chronic pressure overload can lead to concentric left ventricular hypertrophy (LVH), compensatory insu ciency, and subsequent chronic heart failure and CVD events [23]. Although the exact mechanism for this process has yet to be identi ed, physical activity can help prevent LVH or advanced paradoxical regression in those with hypertension [19]. A study of 454 adults from 17 hypertension units (aged 18-45 years; 281 sedentary vs. 173 active) with a long-term (median follow-up of 8.3 years) prospective observation showed that sustained regular physical activity signi cantly decreased BP and prevented the development of LVH [24]. In the present study, both those who constantly participated in physical activity and those who changed from being inactive to engaging in physical activity showed bene cial results related to glucose control, one of the CVD indicators. Therefore, healthcare providers should emphasize the importance of sustained regular physical activity and encourage those are not to begin participating in physical activity, as it is a critical strategy for controlling high BP and reducing the risks of CVD events in older adults with hypertension.
However, in this study, we did not identify clear evidence of the effects of physical activity on obesity or hypercholesterolemia. We de ned obesity as having a BMI ≥ 25kg/m 2 ; however, previous research revealed that older adults improved overall bodily functions when they have a high BMI, such as 30kg/m 2 or over [25]. Therefore, a new standardized value for BMI in older adults needs to be established, and research is needed to identify the recommended range of BMI that can be maintained with appropriate daily physical activity and can prevent CVD events in older adults with hypertension. Low-dose cholesterol medications are commonly used by patients with hypertension since they reduce CVD and atherosclerotic risks [26]. Our sample included older adults diagnosed with hypertension; thus, they may have been prescribed cholesterol-lowering medications, which could have biased the results of this study.
Additional research is needed that can control for the effects of diverse medications taken by the population of older adults.
This study has several limitations. First, this was secondary data analysis, and the responses about physical activity were self-reported by older adults so that they may have been inaccurate or varied from their actual physical activity status. Second, this study did not include information on the participants' use of medical facilities, such as hospital visits, and information on medication use. Research should be conducted that examines the diverse methods of treating hypertension in the older adult population. Regardless, this study's strength is the emphasis on the bene ts of physical activity as a non-pharmacological intervention by investigating the effects on CVD indicators over a period of 12 years in a sample of older adults with hypertension living in the community.

Conclusions
Physical activity is one of the most important non-pharmacological and self-management interventions that can be easily implemented with older adults with hypertension in the community. Our ndings indicate that continuous participation in physical activity can signi cantly lower the long-term CVD indicators in older adults. Healthcare providers should be aware of the importance of physical activity for older adults and encourage them to engage in and maintain it consistently for improved long-term cardio-metabolic outcomes.