Social- and behavioral-specific genetic effects on blood pressure traits: the Strong Heart Family Study

Gene-education interactions identify novel blood pressure loci in the Framingham Heart Study

BACKGROUND

Blood pressure (BP) variability has a genetic component, most of which has yet to be attributed to specific variants. One promising strategy for gene discovery is analysis of interactions between single-nucleotide polymorphisms (SNPs) and BP-related factors, including age, sex, and body mass index (BMI). Educational attainment, a marker for socioeconomic status, has effects on both BP and BMI.

METHODS

We investigated SNP-education interaction effects on BP in genome-wide data on 3,836 subjects in families from the Framingham Heart Study. The ABEL suite was used to adjust for age, sex, BMI, medication use, and kinship and to perform 1 degree-of-freedrom (df) and 2 df SNP-education interaction tests.

RESULTS

An SNP in PTN was associated with increased systolic BP (5.4mm Hg per minor allele) in those without a bachelor's degree but decreased systolic BP (1.6mm Hg per allele) in those with a bachelor's degree (2 df; P = 2.08 × 10(-8)). An SNP in TOX2 was associated with increased diastolic BP (DBP; 4.1mm Hg per minor allele) in those with no more educational attainment than high school but decreased DBP in those with education past high school (-0.7; 1 df; P = 3.74 × 10(-8)). Three suggestive associations were also found: in MYO16 (pulse pressure: 2 df; P = 2.89 × 10(-7)), in HAS2 (DBP: 1 df; P = 1.41 × 10(-7)), and in DLEU2 (DBP: 2 df; P = 1.93 × 10(-7)). All 5 genes are related to BP, including roles in vasodilation and angiogenesis for PTN and TOX2.

CONCLUSIONS

PTN and TOX2 are associated with BP. Analyzing SNP-education interactions may detect novel associations. Education may be a surrogate for unmeasured exposures and behaviors modifying SNP effects on BP.

Six paths for the future of social epidemiology

Social epidemiology is now an accepted part of the academic intellectual landscape. However, in many ways, social epidemiology also runs the risk of losing the identity that distinguished it as a field during its emergence. In the present article, we scan the strengths of social epidemiology to imagine paths forward that will make the field distinct and useful to the understanding of population health in future. We suggest 6 paths to such a future, each emerging from promising research trends in the field in which social epidemiologists can, and should, lead in coming years. Each of these paths contributes to the formation of distinct capacities that social epidemiologists can claim and use to elaborate or fill in gaps in the already strong history of social epidemiology. They present an opportunity for the field to build on its strengths and move forward while leading in new and critical areas in population health.

Recent findings in the genetics of blood pressure and hypertension traits

We provide an overview of ongoing discovery efforts in the genetics of blood pressure (BP) and hypertension (HTN) traits. Two large genome-wide association meta-analyses of individuals of European descent were recently published, revealing ~13 new loci for BP traits. Only two of these loci harbor genes in a pathway known to affect BP (CYP17A1 and NPPA/NPPB). Functional variants in these loci are still unknown. Few genome-wide association studies (GWAS) of complex diseases have been published from non-European populations. The study of populations with different evolutionary history and linkage disequilibrium (LD) structure, such as individuals of African ancestry, may provide an opportunity to further narrow these regions to identify the causal gene(s). Several collaborative efforts toward discovery of low-frequency variants and copy number variation for BP traits are currently underway. As evidence for new loci for complex diseases accumulates the assessment of the epidemiologic architecture of these variants in populations assumes higher priority. The impact of public health-relevant contexts such as diet, physical activity, psychosocial factors, and aging has not been examined for most common variants associated with BP.

Prevalence and risk factors associated with prehypertension: identification of foci for primary prevention of hypertension

BACKGROUND AND RESEARCH OBJECTIVE

Prehypertension (pre-HT) has become an important public health issue in China because it identifies people at higher risk for hypertension (HT) and cardiovascular diseases. The aims of this study were to (1) examine the prevalence of pre-HT, (2) identify risk factors of pre-HT, and (3) identify factors that increase the likelihood of developing HT among the pre-HT group.

SUBJECT AND METHODS

This was a cross-sectional descriptive study. Community-dwelling residents of an urban district in Wuhan, central China (obtained from stratified random sampling), aged between 35 and 74 years completed the study. Data were collected by using a structured self-reporting questionnaire and a standardized protocol for blood pressure measurement and risk screening. Blood pressure categories were defined according to the results of the seventh report of the Joint National Committee on the Prevention, Detection and Treatment of High Blood Pressure.

RESULTS

Among the 1,448 participants, 618 (42.7%) had pre-HT. Multivariate logistic regression analysis revealed the risk factors of being overweight (adjusted odds ratio [aOR], 1.93; 95% confidence interval [CI], 1.26-2.98) or obese (aOR, 8.9; 95% CI, 1.14-62.3) and having above-optimal triglyceride level (aOR, 1.67; 95% CI, 1.24-2.26) were associated with pre-HT. Age and lower educational level were also associated with pre-HT risk. There was a clear trend toward an increased risk of HT among the pre-HT group with every 10-year increment in age starting from 45 years (aORs were 3.47, 6.82, and 7.58, respectively). Participants with Pre-HT currently engaging in sedentary work were also found to have a higher risk of developing HT. Other risk factors for HT included being overweight (aOR, 2.0; 95% CI, 1.50-2.68), a known family history of HT (aOR, 2.54; 95% CI, 1.98-3.26), and presence of diabetes mellitus (aOR, 2.51; 95% CI, 1.66-3.80).

CONCLUSION

Prehypertension is common among residents in an urban district in central China. Findings of this study serve to identify the at-risk groups. Targeting these people early with therapeutic lifestyle changes may provide important long-term benefit for HT prevention.