An increase in coronary heart disease (CHD) risk factors can account for the progressively increasing burden in young patients with CHD. The association between modifiable risk factors and acute myocardial infarction (AMI) is well established, and control of cardiovascular risk factors can reduce the risk of subsequent events.[1] The short-term prognosis in young individuals with CHD may be acceptable compared with older patients; however, the long-term prognosis is poorer in young patients with CHD than in an age-matched population, and these patients have high rates of recurrent events and mortality.[2] Significant disparities have been observed in the prevalence of cardiovascular risk factors between young and older patients with CHD.[2,3] Control of cardiovascular risk factors is insufficient in young patients with CHD,[4] and little is known about whether treatment targets are achieved in young Chinese patients. Therefore, this study aimed to assess the control of cardiovascular risk factors and AMI to identify what risk factors are associated with poor outcomes in young patients with CHD.
This study was based on a cross-sectional analysis of young patients aged 18–44 years who were re-hospitalized with prior CHD in Beijing Anzhen Hospital between January 2007 and December 2017. Clinical and demographic data were collected from the hospital records by trained abstractors, as well as from physicians’ notes, laboratory reports, patients’ medical history, and discharge summaries. Patients with a history of heart transplantation or with arteritis, congenital heart disease, autoimmune disease, or cancer were excluded. Those with missing values for laboratory reports were also excluded. Our study protocol was approved by the Ethics Committee of Beijing Anzhen Hospital (No. 2020085X). All participants gave their written informed consent.
Hypertension and diabetes were defined based on a documented history of hypertension and diabetes in the medical records. We adhered to the recommendations of the Chinese guidelines on cardiovascular disease prevention to define risk factor control. Blood pressure (BP) control was defined as a BP < 140 mmHg/90 mmHg (<130 mmHg/80 mmHg in diabetics). Serum glucose control was defined as hemoglobin A1c (HbA1c) levels <7.0% (diabetics) and low-density lipoprotein cholesterol (LDL-C) control was defined as LDL-C levels <1.8 mmol/L. No smoking was defined as never smoking or cessation of smoking within the last month. Overweight and obesity were defined as a body mass index (BMI) ≥24 kg/m2 and ≥28 kg/m2, respectively. AMI was identified by the Tenth Revision of International Classification of Diseases (ICD-10) code I25.2.
Categorical variables were expressed as the total number (proportion). Differences in risk factor control across groups were compared using the chi-squared test for categorical variables. Normally distributed continuous variables were shown as mean ± standard deviation. Odds ratios (ORs) with 95% confidence intervals (CIs) for associations were derived from multivariable logistic regression. All reported P-values were two-sided. Statistical analysis was performed using IBM SPSS Statistics version 25.0 (IBM Corp, Armonk, NY, USA).
A total of 2599 young patients with prior CHD were re-hospitalized from 1 January 2007 to 31 December 2017. Among these, 2477 (95.3%) were men. A total of 252 (9.7%) patients were aged 18–34 years, 619 (23.8%) were 35–39 years, and 1728 (66.5%) were 40–44 years. Obesity/overweight (83.4%) was the most prevalent risk factor, followed by smoking (60.5%) and hypertension (44.6%). A total of 406 (15.6%) patients had AMI again among these patients.
In 1159 (44.6%) patients with hypertension, the prevalence rate of BP control was 56.0% (n = 649). In 485 (18.7%) patients with diabetes, 169 (34.8%) achieved their target (HbA1c < 7%). In the overall sample, LDL-C levels were below the target level in 554 (21.3%) patients. The prevalence rate of no smoking was 39.5% (n = 1026) and 16.6% (n = 432) of patients had a normal BMI. The prevalence rate of managing LDL-C levels was significantly different between sexes (36.1% in women vs. 20.6% in men; P < 0.001; rate difference: 15.5%). Women had higher prevalence rates of no smoking (95.1% vs. 36.7%; P < 0.001; rate difference: 58.4%) and a normal BMI (45.9% vs. 15.2%; P < 0.001; rate difference: 30.7%). Patients were categorized into three age groups: 18–34 years, 35–39 years, and 40–44 years. We observed significant differences in the prevalence rates of diabetes and no smoking across age groups. Patients aged 18–34 years had the lowest prevalence rates of diabetes (13.9%, P < 0.050) and no smoking (32.9%, P < 0.050). Patients aged 40–44 years had the highest prevalence rates of diabetes (20.3%, P < 0.050) and no smoking (41.1%, P < 0.050). Control of BP, serum glucose levels, LDL-C levels, and BMI were not significantly different across age groups (P > 0.050).
Among the 2599 patients, 406 (15.6%) had AMI. Men had a significantly higher prevalence rate of AMI than women (15.9% vs. 9.0%; P < 0.05; rate difference: 6.9%). Patients aged 18–34 years had a significantly higher prevalence of AMI compared with those aged 40–44 years (24.2% vs. 14.5%; P < 0.05; rate difference: 9.7%). The rates of LDL-C control (11.8% vs. 23.1%; P < 0.001; rate difference 11.3%) and no smoking (29.3% vs. 41.4%; P < 0.001; rate difference: 12.1%) in patients with AMI were lower than those in patients without AMI [Table 1].
Table 1 -
Differences in young patients with and without AMI.
| Characteristics |
AMI (n = 406) |
Non-AMI (n = 2193) |
P-value |
| Gender |
|
|
0.040 |
|  Men |
395 (15.9) |
2082 (84.1) |
|
|  Women |
11 (9.0) |
111 (91.0) |
|
| Age (years) |
|
|
<0.001 |
|  18–34 |
61 (24.2) |
191 (75.8) |
|
|  35–39 |
94 (15.2) |
525 (84.8) |
|
|  40–44 |
251 (14.5) |
1477 (85.5) |
|
| Control of risk factors (%) |
|  Hypertension |
190 (46.8) |
969 (44.2) |
0.331 |
|  BP control |
109 (57.4) |
540 (55.7) |
0.596 |
|  Diabetes |
72 (17.7) |
413 (18.8) |
0.602 |
|  HbA1c < 7% |
23 (31.9) |
146 (35.4) |
0.648 |
|  LDL-C control |
48 (11.8) |
506 (23.1) |
<0.001 |
|  No smoking |
119 (29.3) |
907 (41.4) |
<0.001 |
|  Normal BMI |
65 (16.0) |
367 (16.7) |
0.742 |
Data are presented as n (%). AMI: Acute myocardial infarction; BMI: Body mass index; BP: Blood pressure; HbA 1c: Hemoglobin A1c; LDL-C: Low-density lipoprotein cholesterol.
We also conducted logistic regression analyses to evaluate the relationships between the control of cardiovascular risk factors and AMI. Age (OR = 0.80, 95% CI: 0.69–0.93) and the rates of LDL-C control (OR = 0.48, 95% CI: 0.35–0.66) and no smoking (OR = 0.59, 95% CI: 0.47–0.76) were significantly related to AMI.
In this study of young Chinese patients who were re-hospitalized with prior CHD, 15.6% had a recurrence of AMI and 70.3% repeatedly underwent percutaneous coronary intervention (PCI) or coronary artery bypassing graft (CABG). Control rates of modifiable cardiovascular risk factors were low among the patients. The rate of BP control was the highest (56.0%), followed by that of no smoking (39.5%) and that of LDL-C levels (21.3%). The proportion of normal BMI was only 16.6%. The rates of LDL-C control and no smoking were significantly related to AMI.
The long-term prognosis of young individuals with CHD is poor, and these individuals have high rates of recurrent events. These data are similar to those (14.9%) of patients aged ≤45 years with CHD who were followed up for 20 years.[2] A previous study showed that the rate of secondary reperfusion in young patients was significantly higher than that (70.3% vs. 45.5%) in young patients aged ≤45 years with ST-segment elevation myocardial infarction who were followed up for 15 years.[5] Particularly, the poor long-term outcome of young patients with cardiovascular disease is significantly related to insufficient control of modifiable risk factors.[2]
In this study, rates of controlling modifiable cardiovascular risk factors were low. The DYSIS-China and European studies reported that 26.86% and 25.6%, respectively, of patients with CHD were below guideline-recommended LDL-C target levels (LDL-C levels < 1.8 mmol/L).[6] Control of BP in 55% of patients was also below the target.[6] The CLARIFY registry study showed that the rate of controlled BP in stable CHD with hypertension was 59%.[7] In our study, the rates of controlled LDL-C levels and BP in young patients who were re-hospitalized with prior CHD are similar to those of the above-mentioned CHD population.[7] The rates of controlling some risk factors in our study are lower than those in young patients with CHD in Denmark as follows: LDL-C control (LDL-C levels <1.8 mmol/L): China, 21.3% and Denmark, 42.1%; the non-smoking rate: China, 39.5% and Denmark, 62.9%; and the normal weight rate: China, 16.6% and Denmark, 21.0%. The rate of controlled glucose (34.8%) in young patients with CHD and diabetes is lower than that (46.0%) in patients in the CLARIFY study[7] between 2007 and 2017. Most patients had still not achieved the 2016 Chinese guideline target. Therefore, increased efforts to improve risk factor control are required for secondary prevention in young patients with CHD.
We analyzed the association between the control of cardiovascular risk factors and AMI. In men, lower rates of LDL-C control, normal BMI, and non-smokers were associated with a higher AMI risk than in women. Despite the finding that control rates of modifiable cardiovascular risk factors were low overall, the rates of LDL-C control and no smoking in patients with recurrent coronary events were lower than those in patients without coronary events. Therefore, LDL-C and smoking are the most important risk factors related to the prognosis of young patients with CHD. There were differences in the prevalence of diabetes and the rate of non-smokers between the different age groups. Patients with a lower rate of diabetes and a higher rate of smoking in the low age group had a higher rate of AMI than patients in the high age group. Therefore, smoking is the most powerful predictor of prognosis among young people with CHD.[8]
There are some limitations to this study. This was a single-center study and the data were collected from Beijing Anzhen Hospital, which is well known for managing CHD. Furthermore, the data were collected from a hospital case system, and drug treatment information of young patients with CHD before re-hospitalization was missing.
Among young Chinese patients who are re-hospitalized with prior CHD, the rates of recurrent AMI are high. Rates of controlling modifiable cardiovascular risk factors are low. Insufficient control of modifiable risk factors, especially smoking and dyslipidemia, is the major contributor to poor prognoses. Increasing the LDL-C control rate and cessation of smoking are the most important methods to improve the prognosis of young patients with CHD.
Acknowledgments
The authors wish to thank postgraduates (Haoran Xing, Xueyao Yang, Xin Zhao, Wenyi Zhang, and Xiangru Li) of the Department of Cardiology, Beijing Anzhen Hospital, for extracting data from the electronic records.
Funding
This work was supported by grant from Cardiovascular precision medicine, funded by the Capital Health Development Research Project (No. 2018-2-2063).
Conflicts of interest
None.
References
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