Spontaneous baroreflex sensitivity and its association with age, sex, obesity indices and hypertension: a population study.

BACKGROUND: Low baroreflex sensitivity (BRS) was an established risk factor for cardiovascular disorders. We investigated determinants of BRS in a large sample from general population. METHODS: In a population-based study (n = 901), data were collected on BRS, arm cuff blood pressure (BP), and obesity indices including body mass index, waist-to-hip ratio, waist circumference, and percentage body fat (%BF). BRS was calculated by spectral analysis software based on continuously recorded spontaneous fluctuations in beat-to-beat finger BP for 10-15 minutes. Correlations and multivariable regression analyses were used to test associations of age, sex, obesity indices, and hypertension with BRS while considering effects of lifestyle factors (smoking, alcohol consumption, and physical activity). RESULTS: In multivariable analysis, age, sex, %BF, and hypertension were independently associated with BRS. BRS decreased with -0.10 (95% confidence interval: -0.15 to -0.06) ms/mm Hg with each year of increase in age. Women had -1.55 (95% confidence interval: -2.28 to -0.73) ms/mm Hg lower mean BRS than men. The effects of %BF (per 10% increase) and hypertension on BRS were -0.55 (95% confidence interval: -0.97 to -0.13) ms/mm Hg and -1.23 (95% confidence interval: -1.92 to -0.46) ms/mm Hg, respectively. There was no evidence of associations between BRS and lifestyle factors. Age, age2, sex, and their interactions plus %BF and hypertension contributed 16.9% of total variance of BRS. CONCLUSIONS: In this large general population study, we confirmed prior findings that age and sex were important factors associated with BRS and found %BF was more strongly related to less favorable BRS levels than body mass index.

Heritability and the Genetic Correlation of Heart Rate Variability and Blood Pressure in >29 000 Families: The Lifelines Cohort Study.

Dysregulation of the cardiac autonomic nervous system, as indexed by reduced heart rate variability (HRV), has been associated with the development of high blood pressure (BP). However, the underlying pathological mechanisms are not yet fully understood. This study aimed to estimate heritability of HRV and BP and to determine their genetic overlap. We used baseline data of the 3-generation Lifelines population-based cohort study (n=149 067; mean age, 44.5). In-house software was used to calculate root mean square of successive differences and SD of normal-to-normal intervals as indices of HRV based on 10-second resting ECGs. BP was recorded with an automatic BP monitor. We estimated heritabilities and genetic correlations with variance components methods in ASReml software. We additionally estimated genetic correlations with bivariate linkage disequilibrium score regression using publicly available genome-wide association study data. The heritability (SE) estimates were 15.6% (0.90%) for SD of normal-to-normal intervals and 17.9% (0.90%) for root mean square of successive differences. For BP measures, they ranged from 24.4% (0.90%) for pulse pressure to 30.3% (0.90%) for diastolic BP. Significant negative genetic correlations (all P<0.0001) of root mean square of successive differences/SD of normal-to-normal intervals with systolic BP (-0.20/-0.16) and with diastolic BP (-0.15/-0.13) were observed. LD score regression showed largely consistent genetic correlation estimates of root mean square of successive differences/SD of normal-to-normal intervals with systolic BP (range, -0.08 to -0.23) and diastolic BP (range, -0.20 to -0.27). Our study shows a substantial contribution of genetic factors in explaining the variance of HRV and BP measures in the general population. The significant negative genetic correlations between HRV and BP indicate that genetic pathways for HRV and BP partially overlap.

Heritability and genetic correlations of obesity indices with ambulatory and office beat-to-beat blood pressure in the Oman Family Study.

OBJECTIVE: To more precisely and comprehensively estimate the genetic and environmental correlations between various indices of obesity and BP. METHODS: We estimated heritability and genetic correlations of obesity indices with BP in the Oman family study (n = 1231). Ambulatory and office beat-to-beat BP was measured and mean values for SBP and DBP during daytime, sleep, 24-h and 10 min at rest were calculated. Different indices were used to quantify obesity and fat distribution: BMI, percentage of body fat (%BF), waist circumference and waist-to-height ratio (WHtR). SOLAR software was used to perform univariate and bivariate quantitative genetic analyses adjusting for age, age, sex, age-sex and age--sex interactions. RESULTS: Heritabilities of BP ranged from 30.2 to 38.2% for ambulatory daytime, 16.8--21.4% for sleeping time, 32.1--40.4% for 24-h and 22--24.4% for office beat-to-beat measurements. Heritabilities for obesity indices were 67.8% for BMI, 52.2% for %BF, 37.3% for waist circumference and 37.9% for WHtR. All obesity measures had consistently positive phenotypic correlations with ambulatory and office beat-to-beat SBP and DBP (r-range: 0.14--0.32). Genetic correlations of obesity indices with SBP and DBP were higher than environmental correlations (rG: 0.16--0.50; rE: 0.01--0.31). CONCLUSION: The considerable genetic overlap between a variety of obesity indices and both ambulatory and office beat-to-beat BP highlights the relevance of pleiotropic genes. Future GWAS analyses should discover the specific genes both influencing obesity indices and BP to help unravel their shared genetic background.

Heritability and genetic and environmental correlations of heart rate variability and baroreceptor reflex sensitivity with ambulatory and beat-to-beat blood pressure.

This family study from Oman (n = 1231) explored the heritability and genetic and environmental correlations of heart rate variability (HRV) and baroreceptor reflex sensitivity (BRS) with ambulatory and beat-to-beat blood pressure (BP). Ambulatory BP was measured for 24 hours to calculate mean values for daytime and sleep separately. Time and frequency domain HRV indices, BRS, office beat-to-beat BP, and heart rate (HR) were measured for 10 minutes at rest. SOLAR software was used to perform univariate and bivariate quantitative genetic analyses adjusting for age, age2, sex, their interactions and BMI. Heritability of SBP and DBP ranged from 16.8% to 40.4% for daytime, sleeping, 24-hour and office beat-to-beat measurements. HR and BRS showed a heritability of 31.9% and 20.6%, respectively, and for HRV indices heritability ranged from 11.1% to 20.5%. All HRV measurements and BRS were found to be negatively correlated with BP, but phenotypic correlation coefficients were relatively weak; HR was positively correlated with BP. None of the genetic correlations were statistically significant while environmental factors explained most of the correlations for all HRV indices with BP. Our study found consistent but weak correlations among HRV, HR, BRS and ambulatory/office beat-to-beat BP. However, environmental rather than genetic factors contributed most to those correlations.

Determinants of heart rate variability in the general population: The Lifelines Cohort Study.

BACKGROUND: Heart rate variability (HRV) is an important marker of heart health, with low values reflecting reduced vagal control of the heart rhythm. OBJECTIVE: The purpose of this study was to investigate the extent to which a broad range of demographic (age, sex), lifestyle (physical activity, smoking, alcohol use), and psychosocial factors (stress, social well-being, neuroticism) explain individual differences in HRV in the general population. METHODS: Using baseline data of 10-second electrocardiograms from the Lifelines Cohort Study (n = 149,205; 58.7% female; mean age ± SD: 44.6 ± 13.2 years), we calculated the root mean square of successive differences (RMSSD) between adjacent interbeat intervals as an index of cardiac parasympathetic nervous system activity. We also calculated RMSSD adjusted for its dependency on heart rate (cRMSSD). The association of demographic, lifestyle, and psychosocial factors with RMSSD was assessed using hierarchical linear regression models adjusting for potential confounding effects of medication use, disease, and body mass index. RESULTS: HRV strongly declined with age and was consistently higher in women. These demographic factors together explained 17.4% of the variance in RMSSD and 21.9% in cRMSSD. Physical activity, alcohol use, and smoking showed some significant associations with RMSSD, but stress, social well-being, and neuroticism did not. Adding lifestyle and psychosocial factors to the model additionally explained <0.50% of the variance. CONCLUSION: Age and sex were the most important determinants in this very large general population cohort, explaining almost one-fifth of the individual differences in HRV. The additional contribution of lifestyle and psychosocial factors was negligible.

[The current epidemic situation and surveillance regarding hemorrhagic fever with renal syndrome in China, 2010].

OBJECTIVE: To analyze the surveillance data on hemorrhagic fever with renal syndrome (HFRS) including the epidemiological characteristics and trend of the disease, in 2010. METHODS: Descriptive methods were conducted to analyze the surveillance data in 2010 which were collected from the internet-based National Notifiable Disease Reporting System and 40 HFRS sentinels in China. RESULTS: There were 9526 cases of HFRS reported in 2010 in the country with an annual morbidity of 0.71/10(5), which was higher than that reported in 2009. And the case fatality rate in 2010 was 1.24%. During the year 2010, most cases were reported in spring and autumn-winter season, with November as the peak month. The proportion of cases reported in autumn-winter season was higher than that in spring. The number of cases reported in males was higher than that in females among all the age groups, and similar pattern of mortality could be seen in most of the age groups. The percentage of cases over 60 years old had increased in recent years. Farmers were still under the highest risk. Density and the virus-carrying rate of animal hosts, as well as the infection rate were relatively stable and similar to the previous findings. As to the prevailing species, Apodemus agrarius and Rattus norvegicus were still the most common and leading animal hosts. However, the dominant species in sentinel of Yunnan were Rattus flavipectus and Eothenomys miletus respectively, and a new hantavirus called LUXV was found, namely Eothenomys miletus. CONCLUSION: HFRS cases were widely distributed in most provinces of China, but cases mainly focus on certain areas and present the nature of aggregation. The risk of outbreak could not be ruled out for variety of factors. Population characteristics and seasonal fluctuation had been changing.