Our study found that IDH and ISH were two distinctive types of hypertension. Both of them were age-dependent. However, IDH was more prevalent in young and middle-aged patients, while ISH was more prevalent in middle-aged and old patients. Obesity and smoking, the risk factors for hypertension and lifestyle-changing targets, were significantly associated with IDH but not ISH. Therefore, BMI and smoking habits should be concerned more seriously and might be particularly efficient in young patients with IDH.
Recently, diastolic BP was not considered as important as systolic BP, and IDH was challenged to be regarded as the risk factor for incident cardiovascular outcomes by some studies [3, 16, 17]. Moreover, Mahajan et al. reported that few patients with IDH were aware of having hypertension and were poorly managed in the China PEACE Million Persons Project .
Nevertheless, in a worldwide study, Yan Li et al. reported that IDH was remarkably associated with cardiovascular events, particularly in those below 50 years . Additionally, IDH was associated with urinary albumin/creatinine ratio, particularly in patients below 55 years . The inconsistent results may mainly lie in the age of the study population. It has already been recognized that after 50 years old, the systolic BP continuously increases with age, while on the other hand, the diastolic BP starts to decrease with age. Therefore, IDH is more prevalent in young and middle-aged patients, but ISH is more prevalent in middle-aged and old patients [8, 20]. Thus, the management of IDH should be highlighted rather than ignored in younger patients [21,22,23].
Obesity and smoking are the two major risk factors for the development of hypertension, which can be modified by improving lifestyle management [2, 24]. As obesity and smoking are highly prevalent in young adults, it would be particularly essential to prevent cardiovascular disease by early lifestyle management. BMI trajectories are significantly associated with the incidence of hypertension in young adults, which suggested the importance of early prevention . Recently, smoking has been confirmed to be associated with an increased risk of masked hypertension, especially in heavy smokers . In our study, BMI was remarkably associated with the prevalence of IDH but was not associated with ISH, which might suggest that lowering BMI might be an effective way to lower diastolic BP and improve the management of IDH. Smoking was significantly associated with the prevalence of IDH as well. It was not associated with ISH, either. Thus, giving up smoking might also be exceptionally efficient in the management of IDH. More longitudinal studies are needed in the early IDH interference and management.
The weakness of our study was that it was a cross-sectional study with convenience sampling, which would cause selection bias. The results could not be generalized to those who never came to hospitals and we could not tell the causal relationship between BMI, smoking, and IDH. Patients with ISH were older and might have better lifestyle management after years of medical contact to have lower BMI and smoking rates. Moreover, as we know, patients with hypertension have different weight on risk factors. Other risk factors might affect more in patients with ISH. In addition, unmeasured factors like diet, physical activity levels, socio-economic status, educational levels, and the presence of HMOD were not included in the analysis, which would prevent the study from providing a whole picture of the characteristics of hypertensive patients and would also cause bias. However, we could find that more efforts were needed in lifestyle management concerning BMI and smoking in patients with IDH than those with ISH. Keeping fit and giving up smoking might be critical to lower the diastolic BP and to manage IDH.
The strength of our study was that it was a multi-center study recruiting patients from all over the country with a relatively large sample. Thus, it would be appropriate for the results to be generalized to the hypertensive patients who attend to hospitals in China. Additionally, our study population had a wide span of ages, which facilitated us to depict the features of IDH in relatively young patients and helped fill the insufficiency of data in patients with IDH. The result suggested the importance of lifestyle management in the early-onset patients with IDH, besides antihypertensive agents.
In conclusion, IDH and ISH had different features. Patients with IDH were much younger, and the prevalence decreased with aging. On the contrary, patients with ISH were much older, and the prevalence increased with aging. As IDH was a disease of young and middle-aged patients, such subtype management should be highlighted rather than ignored. BMI and smoking status were the two factors mainly associated with IDH rather than ISH. Besides antihypertensive agents, keeping fit and giving up smoking might contribute a lot to managing young patients with IDH.