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, not only the risk factor for hypertension but also lifestyle-changing targets, were significantly associated with IDH but not ISH. Therefore, the management of 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 if it should be regarded as the risk factor for incident cardiovascular outcomes by some studies[3, 13, 14]. Moreover, Mahajan et al. reported that few patients with IDH were aware of having hypertension, and were poorly managed in the survey of China PEACE Million Persons Project.
But in a worldwide study, Yan Li et al. reported that IDH was remarkably associated with cardiovascular events, particularly in those below age 50. Additionally, IDH was associated with urinary albumin/creatinine ratio, particularly in patients below the age of 55. 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, 17]. Thus, the management of IDH should be highlighted rather than ignored in younger patients.
Obesity and smoking are the two major risk factors for the development of hypertension, which can be modified by improving lifestyle management[2, 19]. As obesity and smoking are highly prevalent in young adults, it would be particularly essential to prevent cardiovascular disease by early lifestyle management in the young. BMI trajectories have been found to be significantly associated with the incident of hypertension in young adults, which suggested the importance of early prevention. Recently, smoking has been confirmed to be associated with 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 especially 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. We could not tell the causal relationship between BMI, smoking, and IDH. But 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.
However, 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.
Additionally, our study population had a wide span of age, 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 totally 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, the management of such type of hypertension should be highlighted rather than ignored. BMI and smoking status were the two factors especially associated with IDH rather than ISH. Besides antihypertensive agents, keeping fit, and giving up smoking might contribute a lot to the management of young patients with IDH.