The present study evaluated the evolution of blood pressure over 18 years with different BP salt-sensitivity from adolescents to youth. There was no significant difference in baseline BP of SS and NSS adolescents, the SS youth showed higher BP increases and significantly higher incidence rate of hypertension than NSS youth. Our findings indicate that adolescents with higher BP salt-sensitivity have a higher rate of incident hypertension in youth.
In 1970s, Luft and Kawasaki proposed the concept of SS based on hypertension patients BP changes and sodium retention responding to high salt intake. A person with salt sensitivity, if long-term exposing to high dietary salt environment, would lead to high blood pressure
[5, 13]. Literatures reported that SS tested varies in different nations and races, ranging from 5% to 25%, the founding in hypertensive patients and population with hypertension family history is about 50%-60% and which is comparatively higher in the senior and the black
[5, 13–15]. In our previous study, it was indicated that about 28% of adults in general population and 60% of hypertensives in China were determined as salt sensitivity
. Follow-up studies have reported that a salt-sensitive state is persistent and reproducible over time
. Furthermore, salt sensitivity was associated with higher incidence of cardiovascular events and increased mortality independent of blood pressure
[18, 19]. In the “New Definition of Hypertension (2005)” of American Society of Hypertension, SS was listed as the sign for early target organ damage by hypertension. Therefore, SS is an important factor in prevention of hypertension and cardiovascular disease.
The essential hypertension mostly originates from children. Following a cohort's BP evolution from their early years to youth has strategic meaning in identifying risk factors for essential hypertension, exploring its pathogenesis mechanism and exerting effective early prevention of hypertension
. There has been major progress in studies, examinations, prevention and treatment of adolescents’ and youth’s hypertension in recent years. The US has established a large-scale national database for regular BP of adolescents, which effectively helps identify and appraise adolescents with abnormal BPs. A study in Spain adolescents showed there was a significant association between salt perception and BP
.However, current studies have not given the evidence on the relationship between sodium and blood pressure in early life
. The Hanzhong Adolescents Hypertension Cohort established in 1980s has been followed up for over 20 years. The current ages of the subjects in the cohort range from 25 to 35 years old, which means that their BP tend to be “steady”. Therefore, this is an important time point to explore the BP evolution from adolescents to adults and the relevant risk factors for hypertension.
A study in a group of American black youth with normal BP showed that, SS subjects with hypertension family history showed significantly higher BP responses to both sodium load and psychological stimulus, indicating that SS might be the genetic risk factor for adolescents’ hypertension pathogenesis
[22, 23]. Recently, a 15-year follow-up study conducted by Barba on a cohort of subjects averagely aged 46 with normal baseline BP showed that, there was significantly higher hypertension incidence rate in SS subjects than in NSS subjects. The logistic regressive analysis indicated that SS is an independent risk factor for pathogenesis of hypertension
. To our knowledge, this is first long-term prospective cohort follow-up study to investigate the predisposing of SS adolescents to essential hypertension in future. These indicated that SS is independent risk factor for adolescents' hypertension pathogenesis and SS adolescents’ high salt intake from childhood plays a determining role in evolution of their BP in later years. Low salt diet, even if as early as in children, may be the the best approach to the prevention of hypertension.
The sample under study was composed of Chinese people only, thus, our findings cannot be extrapolated to other ethnic groups.
The response rate at follow up for surviving baseline samples was 71.9%, with 70.3% for SS subjects and 72.7% for NSS subjects. The response rate was slightly low.
In conclusion, the present study provides long-term prospective data on the incidence of hypertension with different BP salt-sensitivity from adolescents to youth. These indicated that SS is independent risk factor for adolescents' hypertension and SS adolescents’ high salt intake from childhood plays a determining role in evolution of their BP in later years. These results provide further support to the role of salt-sensitivity and dietary salt intake in the pathogenesis of hypertension.