Abstract
Hypertension is a chronic disease that requires long‐term follow‐up in many patients, however, optimal visit intervals are not well‐established. This study aimed to evaluate the incidences of major cardiovascular events (MACEs) according to visit intervals. We analyzed data from 9894 hypertensive patients in the Korean Hypertension Cohort, which enrolled and followed up 11,043 patients for over 10 years. Participants were classified into five groups based on their median visit intervals (MVIs) during the 4‐year period and MACEs were compared among the groups. The patients were divided into clinically relevant MVIs of one (1013; 10%), two (1299; 13%), three (2732; 28%), four (2355; 24%), and six months (2515; 25%). The median follow‐up period was 5 years (range: 1745 ± 293 days). The longer visit interval groups did not have an increased cumulative incidence of MACE (12.9%, 11.8%, 6.7%, 5.9%, and 4%, respectively). In the Cox proportional hazards model, those in the longer MVI group had a smaller hazard ratio (HR) for MACEs or all‐cause death: 1.77 (95% confidence interval [CI], 1.45–2.17), 1.7 (95% CI: 1.41–2.05), 0.90 (95% CI: 0.74–1.09) and 0.64 (95% CI: 0.52–0.79), respectively (Reference MVI group of 75–104 days). In conclusion, a follow‐up visits with a longer interval of 3–6 months was not associated with an increased risk of MACE or all‐cause death in hypertensive patients. Therefore, once medication adjustment is stabilized, a longer interval of 3–6 months is reasonable, reducing medical expenses without increasing the risk of cardiovascular outcomes.
Keywords: cardiovascular event, hypertension, visit intervals
1. INTRODUCTION
Cardiovascular disease is the leading cause of disability and death worldwide, 1 and hypertension is the most important modifiable risk factor of cardiovascular diseases. 2 , 3 With rapid social aging, the absolute hypertensive population has steadily increased; as of 2019, this population has exceeded 12 million in Korea. 2 Naturally, this increase is followed by an increase in medical costs. According to Korean National Health Insurance Service (NHIS) statistics, the estimated total medical cost of treating hypertension is 3.83 trillion Korean Won (2.94 billion USD), accounting for 4% of all medical expenses or 16% of medical expenses for chronic non‐communicable diseases. 4 A recent cost‐effectiveness analysis suggested that more intensive efforts to lower blood pressure with a 50% increase in antihypertensive drug cost and an 8% increase in outpatient costs, is still a cost‐effective strategy through the anticipated reduction of cardiovascular events. 5 , 6 Thus, hypertension control is a cost‐effective national health strategy.
However, hypertension is a chronic disease that requires long‐term follow‐up in many patients. In addition, limited evidence is available regarding optimal outpatient clinic visit intervals. The visit intervals in hypertensive patients depends on several factors, including the severity of the hypertension, combined cardiovascular risk factors, and the frequency and quality of their follow‐up visits. Patients with uncontrolled hypertension, multiple cardiovascular risk factors, and/or inadequate follow‐up are at greater risk for long‐term complications. Additionally, longer visit intervals may increase the risk for long‐term cardiovascular complications, as patients may be more likely to miss check‐ups and/or not have their medications adjusted to adequately address their hypertension. Furthermore, shorter visit intervals are associated with improved outcomes, as patients are more likely to have their medications adjusted and monitored more closely. Conversely, shorter visit intervals might increase healthcare cost and time consuming. The European hypertension guideline recommends that once the blood pressure target is reached, a visit interval of a few months is reasonable, and there might be no difference in blood pressure control between 3‐month and 6‐month intervals. 7 , 8 In the Systolic blood pressure Intervention Trial (SPRINT), three outpatient visits per year for standard treatment and four outpatient visits for intensive treatment were conducted. 9 However, the frequency of outpatient clinic visits in Korea is much higher than that in the United States. Most community clinics recommend monthly visits, whereas tertiary hospitals perform a visit interval of 3−6 months, which is an even become the important reason why hypertensive patients prefer tertiary hospitals. In addition, the fee‐for‐service health system plays a role in frequent outpatient clinic visits. Limited reports suggest that shorter return visit intervals are associated with better blood pressure changes, and it is not certain whether a monthly visit is necessary for hypertensive patients, even after medication adjustment is stabilized. 10
Therefore, we sought to evaluate the impact of visit intervals on cardiovascular events as a sub‐study of the Korean Hypertension Cohort. We aimed to compare the short and long‐term incidences of cardiovascular events according to visit intervals.
2. METHODS
2.1. Study design and data collection
The Korean Hypertension Cohort integrated the detailed clinical and long‐term follow‐up data from six national university hospitals and the NHIS database, respectively. Data of 11,043 hypertensive patients, who were new to each hospital and were mainly diagnosed with hypertension between 2006 and 2011, were analyzed. Follow‐up data on cardiovascular morbidity and mortality were acquired using the NHIS claims data from 2004 to 2018. Furthermore, a control population without hypertension at a 1:10 ratio from the NHIS‐Health Screening Cohort (NHIS‐HEALS) cohort was determined using propensity score matching. 11 The matched variables were sex and age, on a case‐to‐case basis. The full results have been previously published. 12 , 13 , 14 The study protocols were reviewed and approved by the Institutional Review Boards of each participating hospital, including the coordinating center (H‐1810‐056‐977), and the need to obtain informed consent from patients was waived prior to patient enrollment.
The design of this study is illustrated in Figure 1. Among all patients, those with only one visit or no visit records were excluded. When calculating visit intervals and evaluating cardiovascular events, we excluded the first year from the initial hospital visit, because during the initial titration phase, hypertensive patients underwent short, variable visit intervals for medication titration. In addition, cardiovascular events or death during this period were considered to have occurred because of the patients’ previous conditions, and were not related to the visit intervals. Thus, 1 year after enrollment, it was assumed that drug prescriptions and visits were fixed as a maintenance phase. We calculated the visit intervals for the first 4 years of the maintenance period (2−5 years after enrollment). The visit interval was defined as the number of days between outpatient clinic visits. Patients were divided into five visit interval groups according to the clinically relevant median visit intervals (MVIs), such as 1, 2, 3, 4, and 6 months. With the 15 days of visit windows, the groups were categorized as 0−44 days, 45−74 days, 75−104 days, 105−134 days, and 135−200 days, respectively. In Korea, the guideline stipulates a maximal follow‐up interval of six months for hypertensive patients, and the medical insurance system does not reimburse longer follow‐up intervals. Considering this background, we excluded cases with an estimated follow‐up interval of more than 200 days from the analysis as they might be due to follow‐up loss rather than a scheduled visit. The follow‐up duration was 5 years including the maintenance phase.
FIGURE 1.
Study design.
2.2. Definition of cardiovascular diseases, risk factors, and medication adherence
Hypertension was defined as systolic/diastolic blood pressure ≥140/90 mmHg without antihypertensive treatment or ≥130/80 mmHg with antihypertensive treatment. Clinical cardiovascular diseases, and cardiovascular risk factors were defined according to the Korean Society of Hypertension guidelines. 15 , 16 The high cardiovascular risk group included patients with clinical cardiovascular diseases, stroke, chronic kidney disease, or diabetes mellitus. The moderate cardiovascular risk group was defined as patients with left ventricular hypertrophy, increased vascular stiffness, or metabolic syndrome, excluding those with diabetes mellitus. The low cardiovascular risk group was defined as patients who did not belong to either the high‐ or moderate‐ risk group. For the NHIS data analysis, operational definitions of cardiovascular diseases were followed by the paper by Choi and colleagues. 17
The medication possession ratio (MPR) is a measure of the adherence. Adherence is the degree to which a patient conforms to a prescribed course of medication, whereas persistence refers to conformity with the prescribed period of treatment. 18 Formally, MPR is defined as the sum of the days’ supplies of medication during a period divided by the number of the period. 19 While the level of optimal adherence may differ for different clinical conditions, persistency is usually defined as adherence (or MPR) of ≥80%. 20
2.3. Statistical analysis
The primary composite outcomes of this study were all‐cause death and major cardiovascular events (MACE) including heart failure, myocardial infarction, peripheral arterial disease, hemorrhagic stroke, ischemic stroke, and end‐stage renal disease. 13 Data are reported as means ± standard deviations (SDs) or medians (interquartile ranges) for continuous variables, and as numbers (percentages) for categorical variables. Statistical significance was set at p‐value < .05. The Kaplan‐Meier method was used to compare the differences in the cumulative incidences of MACE and all cause deaths during the follow‐up period among the five visit interval groups. The effects of visit interval on cardiovascular outcomes were assessed using the Cox proportional hazards model. We estimated the hazard ratios (HRs) and their corresponding 95% confidence intervals (CIs) relating visit intervals to cardiovascular outcomes. A post‐hoc analysis was conducted with subgroups of age, sex, and cardiovascular risks to adjust for potential selection bias. The detailed statistical analysis method has been described previously. 12 , 13 Statistical analyses were performed using SAS (version 9.4, SAS Institute, Cary, NC) and R software (version 4.0.3; R project).
3. RESULTS
3.1. Baseline characteristics and visit frequency of patients
A total of 9894 hypertensive patients from the Korean Hypertension Cohort study were enrolled (Figure 2). The mean number of visits ± SD was 33.87 ± 21.34 for 4 years. The overall follow‐up duration was 1745 ± 293 days. The baseline characteristics of the hypertensive population are shown in Table 1. Among the participants at baseline, the mean age was 58.7 years, 50% were men, and 59.2% had previously been treated of hypertension. The initial blood pressure in the maintenance phase was 131.8 ± 10.8/78.8 ± 7.7 mmHg. Overall, 24.6% had high cardiovascular risk, 17.8% had moderate risk, and 57.6% had low risk. Medication adherence measured by MPR was 0.74 ± 0.22, and no statistically significant difference was identified between the groups. Moreover, 35.8% of the patients belonged to the high medication‐persistent category, defined as MPR > 0.80.
FIGURE 2.
Flow diagram of the study.
TABLE 1.
Characteristics of hypertensive patients according to hospital visit interval.
| Variable | Hospital visit interval | ||||||
|---|---|---|---|---|---|---|---|
| 0‐44 days | 45‐74 days | 75‐104 days | 105‐134 days | 135‐200 days | Total | ||
| (N = 1013) | (N = 1299) | (N = 2732) | (N = 2335) | (N = 2515) | (N = 9894) | p‐value | |
| Age at index date, (years) | 59.6 ± 12 | 59.4 ± 12.4 | 59.6 ± 11.5 | 58 ± 11.3 | 57.8 ± 10.7 | 58.7 ± 11.5 | <.001 |
| Male, n (%) | 444 (43.8%) | 598 (46%) | 1384 (50.7%) | 1244 (53.3%) | 1273 (50.6%) | 4943 (50%) | <.001 |
| SBP (mmHg)_history | 133.5 ± 12.8 | 132.8 ± 11.9 | 132.4 ± 11.1 | 131.5 ± 9.9 | 130.1 ± 9.7 | 131.8 ± 10.8 | <.001 |
| DBP (mmHg)_history | 79.3 ± 8.4 | 78.9 ± 8.6 | 78.7 ± 8 | 79.1 ± 7.4 | 78.5 ± 6.7 | 78.8 ± 7.7 | .004 |
| Previous HTN treatment, n (%) | 663 (65.4%) | 824 (63.4%) | 1655 (60.6%) | 1326 (56.8%) | 1394 (55.4%) | 5862 (59.2%) | <.001 |
| Cardiovascular risk, n (%) | <.001 | ||||||
| High risk | 285 (28.1%) | 345 (26.6%) | 799 (29.2%) | 557 (23.9%) | 443 (17.6%) | 2429 (24.6%) | |
| Moderate risk | 184 (18.2%) | 209 (16.1%) | 449 (16.4%) | 406 (17.4%) | 517 (20.6%) | 1765 (17.8%) | |
| Low risk | 544 (53.7%) | 745 (57.4%) | 1484 (54.3%) | 1372 (58.8%) | 1555 (61.8%) | 5700 (57.6%) | |
| MPR (mean ± SD) | 0.74 ± 0.46 | 0.73 ± 0.23 | 0.74 ± 0.16 | 0.74 ± 0.15 | 0.74 ± 0.15 | 0.74 ± 0.22 | .043 |
| >0.80 | 323 (31.9%) | 447 (34.4%) | 1004 (36.7%) | 856 (36.7%) | 911 (36.2%) | 3541 (35.8%) | |
| <0.80 | 690 (68.1%) | 852 (65.6%) | 1728 (63.3%) | 1479 (63.3%) | 1604 (63.8%) | 6353 (64.2%) | |
| Follow‐up duration (days) | 1672 ± 416 | 1688 ± 381 | 1750 ± 281 | 1763 ± 256 | 1784 ± 204 | 1745 ± 293 | <.001 |
| CVD incidencea | <.001 | ||||||
| MACE | 28.3 | 25.5 | 14.1 | 12.2 | 8.1 | 15.0 | |
| Death | 7.1 | 9.3 | 6.1 | 4.2 | 2.9 | 5.0 | |
| MACE + Death | 35.4 | 34.8 | 20.2 | 16.4 | 11.0 | 20.0 | |
Abbreviations: BMI, body mass index; DBP, diastolic blood pressure; MACE, major adverse cardiovascular events; MPR, Medication possession ratio; SBP, systolic blood pressure; SD, standard deviation.
The data presented are the incidence rates (cases/1000 person‐years).
For all visits, the MVI was 98.75 ± 50.0 days. The MVI of each patient during the 4‐year maintenance period were classified into five groups, as follows: 0−44 days, 45−74 days, 75−104 days, 105−134 days, and 135−200 days, which represent 1, 2, 3, 4, and 6 months, respectively. Of the 9894 patients, 10% visited the clinic with MVIs of 0−44 days, followed by MVIs of 45−74 days (13%), 75−104 days (28%), 105−134 days (24%), and 135−200 days (25%) (Supplemental Figure 1). Patients in the longer MVI group had a lower average systolic blood pressure (p < .001) and diastolic blood pressure (p < .005) values. Patients in the longer MVI group also had a lower proportion of previous hypertension treatments (p < .001). Patients in the largest MVI group of 135−200 days had the lowest percentage of patients in the high cardiovascular risk group (17.6%) (p < .001). The proportion of participants who had MPR values > 0.80 was greater in the longer MVI groups than that in the shorter MVI groups.
3.2. Cardiovascular events according to follow‐up intervals
During the median follow‐up of 5 years (1745 ± 293 days), excluding events that occurred during the first year of the initial titration phase, 706 (7.1%) MACE and 252 (2.5%) all‐cause deaths occurred in this cohort. The overall incidence rates (per 1000 person‐years) of MACE or deaths were 15.0 and 5.0, respectively (Table 1). The incidence rates of MACEs or death were significantly lower in patients with longer visit intervals (28.3, 25.5, 14.1, 12.2, and 8.1 events per 1000 person‐years in MVI groups of 1, 2, 3, 4, and 6 months, respectively; p < .001). Figure 3 shows the Kaplan‐Meier curves for the cumulative incidence of MACEs or death in the five visit interval groups. The longer MVI groups showed smaller cumulative incidences of cardiovascular events or death. And shorter MVI groups showed consistently higher event rates.
FIGURE 3.
Cumulative incidence of cardiovascular events or death according to the visit interval groups.
The association between the MVIs and cardiovascular events was evaluated. In the Cox proportional hazards model, the patients with hypertension in the longer MVI groups had fewer incidences of MACEs or death. The crude HR of the longer MVI groups, compared with that of the reference MVI group of 3 months, were 0.81 (95% CI: 0.67−0.98; p = .035) and 0.56 (95% CI: 0.45−0.69; p < .001), respectively. In contrast, the shorter interval groups showed a higher rate of MACE, as follows: 1.76 (95% CI: 1.44−2.15; p < .001) in the MVI group of 1 month and 1.67 (95% CI: 1.38−2.01; p < .001) in the MVI group of 2 months, respectively (Table 2). Even in the context of multivariate regression analysis, adjusting for age, sex, systolic blood pressure, diastolic blood pressure, previous hypertension treatment, and baseline cardiovascular risk, the shorter MVI groups showed high risks, whereas the longer MVI groups did not show increased event rates.
TABLE 2.
Cox proportional hazard model for cardiovascular events or death regarding visit intervals in hypertensive population.
| Variable | Multivariable analysis MPR (≥0.8) | Multivariable analysis MPR (< 0.8) | ||
|---|---|---|---|---|
| HR (95% CI) | p‐value | HR (95% CI) | p‐value | |
| Hospital visit interval (median) | ||||
| 0‐44 days | 1.91 (1.42‐2.55) | <.001 | 2.07 (1.40‐3.06) | <.001 |
| 45‐74 days | 1.57 (1.20‐2.06) | .001 | 2.03 (1.42‐2.92) | <.001 |
| 75‐104 days | 1 (Ref) | 1 (Ref) | ||
| 105‐134 days | 0.85 (0.65‐1.12) | .256 | .92 (.63‐1.36) | .685 |
| 135‐200 days | 0.57 (0.42‐0.78) | <.001 | .64 (.41‐.98) | .042 |
| Age | 1.03 (1.02‐1.04) | <.001 | 1.02 (1.01‐1.04) | <.001 |
| Male | 1.25 (1.04‐1.52) | .020 | 1.40 (1.08‐1.81) | .011 |
| SBP (Mean) | 1.01 (1.00‐1.01) | .229 | 1.02 (1.00‐1.03) | .009 |
| DBP (Mean) | 1.00 (0.99‐1.02) | .961 | .97 (.95‐.99) | .003 |
| Previous HTN treatment | 1.04 (0.84‐1.28) | .728 | 1.04 (.79‐1.36) | .784 |
| BMI(≥25) | 0.92(0.76‐1.12) | .404 | .72 (.56‐.94) | .014 |
| DM | 1.10(0.84‐1.44) | .495 | 1.17 (.83‐1.66) | .374 |
| CKD | 1.40(0.88‐2.33) | .157 | 2.81(1.69‐4.69) | <.001 |
Abbreviations: CI, Confidence interval; DBP, Diastolic blood pressure; HR, Hazard ratio; HTN, Hypertension; SBP, Systolic blood pressure; SD, Standard deviation.
Finally, we performed subgroup analysis stratified by age, sex, and baseline cardiovascular risk. There was no heterogeneity among the cardiovascular event rates according to the visit intervals (Figure 4).
FIGURE 4.
Subgroup analysis of cardiovascular events or death according to the age, sex, and baseline cardiovascular risk categories.
4. DISCUSSION
In the present study, we evaluated the association between outpatient clinic visit intervals and cardiovascular events or all cause death in hypertensive patients of the Korean Hypertension Cohort in a large‐volume, long‐term follow‐up cohort. A considerable proportion of the patients frequently visited the outpatient clinic; 23% of patients visited the hospital every 1−2 months, even during the long‐term follow‐up period. However, a longer hospital visit interval of 3−6 months was not associated with an increase in the incidence of cardiovascular events or death in patients with hypertension. Rather, the results of this study showed lower cardiovascular event rates in the groups with longer visit intervals. We cannot rule out the possibility of selection bias, as physicians recommended longer hospital visit intervals for more stable patients. However, regardless of how conservative treatment was, a longer visit schedule of 3−6 months was not associated with increased cardiovascular events or death. The results were consistent across sex, age, and baseline cardiovascular risk.
Most of the results of this study might be attributed to the high medication adherence of the patients. There is concern that longer visit intervals increase the risk of missed hospital visit resulting in reduced medication adherence. 21 Especially in the public health sector, there is an unofficial recommendation to avoid long‐term medication prescriptions. The reason behind this is that even though requiring hypertension patients to visit the hospital every month for medication prescription may result in increased medical costs for service fee, there is concern that longer visit intervals may lead to reduced compliance and increased cardiovascular diseases and medication costs (Personal communication). However, in this study, the MPR was similar regardless of visit intervals. The MPR was ≥0.75 and 36% of the patients were persistently adherent to the medication, with an MPR of ≥0.8. 20 Therefore, the results of this study should be interpreted with caution, as longer visit intervals are feasible in patient groups with adherence rates maintained throughout the visit window. However, another study was also suggested that the short visit intervals were not beneficial in maintaining treatment adherence, 22 which is consistent with our study.
Other studies have shown contradictory results. A shorter return visit interval was associated with better blood pressure control, attributed to physicians being able to prescribe and adjust medications in a timely manner. 23 , 24 However, there were differences in the study settings. Previous studies have investigated the visit intervals of patients during the entire follow‐up period, including the initial titration phase when frequent visits for dose titration and medication adjustment are required. Unlike other studies, we investigated visit intervals only during the maintenance period, after 1 year following the first hospital visit, assuming that the titration of antihypertensive medication might be set to reach a maximum of 1 year. Therefore, we suggest that once medication prescriptions and adjustments are stabilized, frequent hospital visits are unnecessary. Second, the results of this study suggest that a shorter visit interval may not be beneficial for medication adherence. The MPRs were greater in the longer visit interval group, indicating better treatment adherence. This is contrary to the opinion that frequent visits would increase medication adherence. Therefore, we suggest that a long visit interval of 3−6 months is recommended during the maintenance period of patients with hypertension. This strategy can save huge amount of economic benefit without increasing cardiovascular risk. The number of hypertensive patients in South Korea is approximately 7 million, and the average cost of outpatient treatment is 22,500 Korean won (∼$18.98 USD) per visit (as of 2021). Therefore, if one patient visits the clinic every month for five years, the cost would be 1,350,000 won (∼$1,142.90 USD) for 60 visits. However, according to this study, if the patient visits the clinic every three or six months for the remaining 4.5 years after dose adjustment for the first six month by monthly visits, they can reduce their medical expenses by 60−75%. This amounts to a total potential medical cost savings of up to 7 trillion won ($6 billion USD). 5 , 6
This study offers real‐world evidence by merging deep phenotypic data from hospital data and long‐term follow‐up by utilizing big public health data. Korea has a single government‐maintained NHIS that provides free biennial health examination data, medical services, and pharmacy claims data. 11 , 25 , 26 However, there is a lack of detailed clinical data in the health claims database, especially in terms of blood pressure values, which may include critical chronic disease data that require repetitive measurement of clinical factors. In contrast, hospital data based on electronic medical records offer repetitive values of critical parameters, such as blood pressure, heart rate, blood chemistry over time, and specialized laboratory data including electrocardiograms, echocardiograms, ambulatory blood pressure monitoring, and arterial stiffness measurements. Therefore, we can offer comprehensive data in long‐term cardiovascular event rates according to the cardiovascular risk.
This study had certain limitations. The design of the study was not a clinical trial but a retrospective study of a patient cohort. Patient assessments, management, and follow‐up regimens were not standardized and varied among the included institutions. Therefore, treatment results might be affected by the patients; intrinsic risks rather than differences in treatment patterns, especially when classifying patients into each visit interval groups. This can be inferred because patients with longer visit intervals had a lower baseline systolic blood pressure cardiovascular risk. However, the risk of bias was minimized by (1) conducting multivariable analysis with adjustment of age, sex, and baseline cardiovascular risk; (2) conducting subgroup analysis to estimate the effects of potential confounding variables (age, sex, and baseline cardiovascular risk); and (3) excluding cardiovascular events that occurred within 1 year after the first visit. In the subgroup analyses, there was no significant heterogeneity between the following groups: age of ≥ and ≤60, men and women, and high and low cardiovascular risk groups. None of the subgroups indicated that a longer visit interval caused negative cardiovascular outcomes. We still cannot rule out the possibility of non‐random allocations affecting the results; however, a retrospective cohort study is a pragmatic design for long‐term follow‐up with a large sample size study. In addition, the participant selection was limited to patients from tertiary hospitals. The remarkable finding of this study was that the MPR was high regardless of MVIs. However, early refilling would lead to an MPR of > 1.0, leading to an overestimation of adherence. The sample cannot represent the entire Korean population with hypertension, such as patients from local clinics and community hospitals. However, most enrolled patients with hypertension were gradually referred back from tertiary hospital to community clinics during follow‐up. Also, the study using the NHIS data from 2007 to 2011 reported the similar rate of MPR of 0.76, 27 suggesting that MPR in hypertensive patients treated by non‐university hospitals in Korea might be similar. Lastly, we did not evaluate the blood pressure visit‐to‐visit variability, which is well‐known important cardiovascular risk factor, during follow up, because the claim data do not include blood pressure information. Despite these limitations, this study, with a large volume and long‐term follow‐up, is first to show that long visit intervals in the maintenance phase do not increase the risk of cardiovascular events in patients with hypertension. Further studies with a randomized design would help verify this result and establish standards for the management of hypertension.
In conclusion, a follow‐up visits with a longer interval of 3−6 months was not associated with an increased risk of cardiovascular events or death in hypertensive patients. Therefore, once medication adjustment is stabilized, a longer interval of 3−6 months is reasonable to reduce medical expenses without increasing the risk of cardiovascular outcomes.
AUTHOR CONTRIBUTIONS
This study was coordinated by Hae‐Young Lee as the principal investigator. Hyunmook Jeong, Suhyun Kim, Kwangsoo Kim and Seungyeon Kim analyzed the data. Ho‐Gyun Shin, Kyun‐Ik Park, Ju‐Yeun Lee, Sue K. Park organized the KHC. Hee‐Sun Lee, Kwang‐il Kim, Si‐Hyuck Kang, Jang Hoon Le, Se Yong Jang, Ju‐Hee Lee, Kye Hun Kim, Jae Yeong Cho, Jae‐Hyeong Park contributed equally to data collection and validation. Duon Kim and Hyunmook Jeong equally contributed to writing and original draft preparation.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflicts of interest.
PATIENT CONSENT STATEMENT
The need to obtain informed consent from patients was waived prior to patient enrollment.
Supporting information
Supplementary information
ACKNOWLEDGMENTS
This study was supported by the Ministry of Health and Welfare (grant number NA20‐001, HYL) and by the Korea Government Grant Program for Education and Research in Medical AI through the Korea Health Industry Development Institute (KHIDI) (DK). This research was supported by the National Evidence‐based Healthcare Collaborating Agency (NECA) and the Korean Society of Hypertension. We thank Tae Hyun Kim for help with the cost‐effectiveness analysis.
Kim D, Jeong H, Kim S, et al. Association between office visit intervals and long‐term cardiovascular risk in hypertensive patients. J Clin Hypertens. 2023;25:748‐756. 10.1111/jch.14698
Duon Kim and Hyunmook Jeong equally contributed to the study
DATA AVAILABILITY STATEMENT
The entire analysis process of the linked data sources was conducted in the NHIS data analysis office. External exportation of the data and additional extraction of personal information were not permitted. The authors are restricted from sharing the data underlying this study because the Korean NHIS owns the data.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supplementary information
Data Availability Statement
The entire analysis process of the linked data sources was conducted in the NHIS data analysis office. External exportation of the data and additional extraction of personal information were not permitted. The authors are restricted from sharing the data underlying this study because the Korean NHIS owns the data.