Obesity and season as determinants of high blood pressure in a school-based screening study

Seasonal variation of ambulatory blood pressure in Chinese hypertensive adolescents

BACKGROUND

Blood pressure (BP) exhibits seasonal variation with lower levels at higher temperatures and vice versa. This phenomenon affects both sexes and all age groups. So far, only a few research studies have investigated this condition in adolescents and none of them were based on hypertensive population or ever applied ambulatory blood pressure monitor (ABPM). Therefore, we carried out the first study that used ABPM to record seasonal variation of blood pressure in hypertensive adolescents.

METHODS

From March 2018 to February 2019, 649 ABPMs from hypertensive adolescents between 13 and 17 years who were referred to wear an ABPM device in Beijing and Baoding were extracted. Seasonal change in ambulatory BP value, dipping status, and prevalence of different BP phenotypes were analyzed and compared.

RESULTS

Mean age of participants was 14.9 ± 1.5 years and 65.8% of them were boys. Of the participants, 75.3% met the criteria of overweight or obesity. From summer to winter, average 24-hour, day-time, and night-time BP showed significant rise, which was 9.8/2.8, 9.8/3.0, and 10.9/3.4 mmHg, respectively. This seasonal effect on BP was not dependent on the obesity degree. In addition, higher prevalence of nondippers and risers existed in winter while white coat hypertension was more frequent in warmer seasons.

CONCLUSION

Hypertensive adolescents showed evident seasonal change in their ABPM results, which was featured by elevated BP level and more frequent abnormal dipping patterns in winter. On the contrary, higher prevalence of white coat hypertension was found in warmer seasons. Physicians should take seasonal variation into consideration when managing adolescent hypertension.

Seasonal variation of ambulatory blood pressure in Chinese hypertensive adolescents

BACKGROUND

Blood pressure (BP) exhibits seasonal variation with lower levels at higher temperatures and vice versa. This phenomenon affects both sexes and all age groups. So far, only a few research studies have investigated this condition in adolescents and none of them were based on hypertensive population or ever applied ambulatory blood pressure monitor (ABPM). Therefore, we carried out the first study that used ABPM to record seasonal variation of blood pressure in hypertensive adolescents.

METHODS

From March 2018 to February 2019, 649 ABPMs from hypertensive adolescents between 13 and 17 years who were referred to wear an ABPM device in Beijing and Baoding were extracted. Seasonal change in ambulatory BP value, dipping status, and prevalence of different BP phenotypes were analyzed and compared.

RESULTS

Mean age of participants was 14.9 ± 1.5 years and 65.8% of them were boys. Of the participants, 75.3% met the criteria of overweight or obesity. From summer to winter, average 24-hour, day-time, and night-time BP showed significant rise, which was 9.8/2.8, 9.8/3.0, and 10.9/3.4 mmHg, respectively. This seasonal effect on BP was not dependent on the obesity degree. In addition, higher prevalence of nondippers and risers existed in winter while white coat hypertension was more frequent in warmer seasons.

CONCLUSION

Hypertensive adolescents showed evident seasonal change in their ABPM results, which was featured by elevated BP level and more frequent abnormal dipping patterns in winter. On the contrary, higher prevalence of white coat hypertension was found in warmer seasons. Physicians should take seasonal variation into consideration when managing adolescent hypertension.

Seasonal variation of blood pressure in children

Seasonal blood pressure (BP) variation is mostly found between the summer and winter months. Guidelines for diagnosis and treatment of hypertension in children have not considered this variation until recently. This review aims to present an overview of seasonal BP variation in childhood along with potential underlying pathophysiological mechanisms and long-term implications as well as conclusions for future studies. In pediatric cohorts, seven studies investigated seasonal changes in BP. These changes amount to 3.4-5.9 mmHg (or 0.5-1.5 mmHg per - 1 °C difference in environmental temperature) in systolic BP with a peak in fall or winter. Potential mechanisms and mediators of seasonal BP variation include sympathetic activation of the nervous system with an increase of urinary and plasma norepinephrine levels in the winter season. Additionally, the physical activity among children and adolescents was inversely correlated with BP levels. Temperature sensitivity of BP and pediatric BP levels predict future systolic BP and target-organ damage. Therefore, cardiovascular events may even be long-term complications of seasonal BP variation in pediatric hypertensive patients. Overall, these data strongly suggest an important effect of ambient temperature on BP in children. Additional studies in pediatric cohorts are needed to define how best to incorporate such variation into clinical practice.

Ambulatory hemodynamic patterns, obesity, and pulse wave velocity in children and adolescents

BACKGROUND

In recent years, pulse wave velocity (PWV) has emerged as a surrogate marker of cardiovascular disease in children with cardiovascular risk factors. The aims of the present study were to identify determinants of PWV in children according to their weight status and to investigate the role of peripheral blood pressure and central hemodynamic parameters in the association between PWV and obesity.

METHODS

We included in the study healthy children and adolescents randomly selected from a school-based blood pressure screening study. All participants underwent ambulatory blood pressure monitoring and 24-h pulse wave analysis.

RESULTS

Overweight and obese children had higher 24-h PWV, 24-h peripheral and central systolic blood pressure (SBP), and cardiac output than normal weight ones. Children with both overweight and hypertension presented the highest 24-h PWV values (p < 0.001). Peripheral and central SBP, body mass index (BMI), and hemodynamic parameters, including stroke volume, cardiac output, total peripheral resistance, and cardiac index, were all associated with 24-h PWV. However, in stepwise regression analysis, 24-h peripheral and central SBP and cardiac index, but not BMI, were independent predictors of 24-h PWV. There were statistically significant differences in 24-h blood pressure and hemodynamic parameters among those on the lower and highest 24-h PWV quartile, but there were no significant differences in BMI among 24-h PWV quartile groups.

CONCLUSIONS

Arterial stiffness is higher in overweight and obese children in the co-presence of hypertension. Peripheral and central SBP are the main determinants of 24-h PWV independent of weight status. Graphical abstract.

Arterial stiffness in children and adolescents with masked and sustained hypertension

This study recruited 85 healthy children and adolescents, aged 6-18 years, from a school-based blood pressure (BP) screening study and performed office BP measurements, 24-h ambulatory blood pressure monitoring (24-h ABPM) and 24-h pulse wave analysis. Prevalence of BP phenotypes was assessed, factors that may predict hypertension (HTN) in ABPM were examined and the effect of BP phenotypes, as well as school, office, and ambulatory BP parameters on pulse wave velocity (PWV), was investigated. Forty-five (54.9%) of the children were normotensives, 8 (9.7%) were white coat hypertensives (WCH), 19 (23.2%) had masked hypertension (MH), and 10 (12.2%) had sustained HTN. Estimated adjusted marginal means for 24-h PWV were 4.79 m/s (95% CI 4.65-4.94) for sustained hypertensives, 4.72 m/s (95% CI 4.62-4.82) for MH, 4.38 m/s (95% CI 4.23-4.54) for WCH, and 4.33 m/s (95% CI 4.26-4.40) for normotensives (sustained hypertensives versus normotensives and WCH, p < 0.001, MH versus normotensives and WCH, p < 0.005). Neither body mass index (BMI) z-score nor school systolic BP (SBP) z-score could predict HTN by ABPM. Office SBP z-score was associated with 1.74 times increased odds ratio to have HTN in ABPM. Sustained HTN and MH were independent predictors of 24-h PWV after adjustment for age, sex, and BMI z-score. In conclusion, arterial stiffness in children and adolescents was assessed by 24-h PWV associates with mean ambulatory BP. Both school and office BP measurements could not predict HTN in ABPM or increasing PWV. HTN in ABPM was independently associated with the risk of higher PWV compared with normotensive and WCH phenotype.