Hypertension among relatives of hypertensives: progress report of a family study

Arterial pressures in a general practice

Systolic and diastolic readings of blood pressure were recorded for 5386 (2585 males and 2801 females) members of a general practice situated in and around Ballycastle, County Antrim. Polynomials to predict blood pressure from age were derived for systolic and diastolic pressures of males and females. Polynomials to predict blood pressure variance from age were derived for both systolic and diastolic pressure of each sex. Age-sex adjusted diastolic and systolic scores were calculated for each of the 5386 members of the practice using a technique similar to that reported by Hamilton et al. (1954 a, b).Parent-child correlations ranging from -0.21 to 0.17 were observed; however, when all sibships were considered together irrespective of size coefficients which were significantly greater than zero generally involved the mother of the child. No sib-sib correlation (all sibship sizes combined), except those involving twins exceeded the value 0.13. Husband-wife correlations were similar to the corresponding parent-offspring correlations when both husband and wife were aged 45 years or more. Generally speaking, the coefficients found in this study were lower than those of other workers and reasons are discussed why the estimates of the present paper may not be unbiased.

Are spouses of patients with hypertension at increased risk of having hypertension? A population-based case-control study

BACKGROUND

Studies of couples, who tend to share an environment but are genetically dissimilar, can shed light on the contribution of environmental factors to hypertension. There has been renewed interest in these environmental factors following the re-analysis of the INTERSALT study.

AIM

To determine whether patients whose spouses have hypertension are at increased risk of hypertension, using a population-based case-control study.

METHOD

The total study population consisted of all 3923 patients over 30 years old registered with one general practice. Male cases with hypertension were matched to male controls without hypertension. Female cases with hypertension were matched to female controls without hypertension. The variables were: diagnosed hypertension; having a spouse with diagnosed hypertension; age; sex; weight; height; body-mass index; couple status; diabetes; and systolic and diastolic blood pressure readings.

RESULTS

On multivariate analysis, when age, body-mass index, diabetes, couple status, and having a blood pressure reading were included, men whose spouses had hypertension had a two-fold increased risk of hypertension (adjusted odds ratio (OR) 2.24; 95% CI 1.77-2.72; P = 0.001). Similarly, on multivariate analysis, women whose spouses had hypertension had a two-fold increased risk of hypertension (adjusted OR = 2.23; 95% CI 1.75-2.72; P = 0.001). The risk for both male and female subjects persisted after adjustment for other variables. There was a significant correlation between systolic (r = 0.41; P < 0.0001) and diastolic (r = 0.25; P < 0.0001) blood pressures between spouse pairs.

CONCLUSION

The independent association between having a spouse with hypertension and increased risk of hypertension supports the view that there are significant environmental factors in the aetiology of hypertension. The finding has implications for the screening and treatment of hypertension in primary care.

The effects of age, gender, and family history on blood pressure of normotensive college students

Offspring with a parental history of hypertension are, by some estimates, four times more likely to develop the disease (Corvol et al., 1992). While some studies suggest that an increased risk is observable in eight year old children, others suggest that the increased risk does not become apparent until age 20. This study examined this discrepancy by screening resting blood pressures from 403 young adults. After adjusting for body mass, a significant family history x age x gender interaction (p < .01) suggests that the effect of family history on systolic blood pressure varies by age and gender. The influence of positive family history becomes apparent in males by age 20 and in females by age 22. This relationship may help provide a rationale for interpretation and reconciliation of disparate results in the literature, and clarify our understanding of the etiologic mechanisms responsible for development of essential hypertension.

Selection bias in the study of spouse similarity for psychiatric morbidity in clinical samples

The existing literature on spouse similarity for health variables can be divided into two fields of application, high blood pressure and other coronary risk factors and psychiatric morbidity. In the former field, almost all studies have been conducted on general-population samples, whereas in the psychiatric field, most of the investigations studied clinical samples, i.e., where one or both members of the couple were under psychiatric treatment. In this report, we demonstrate that studies of spouse similarity for psychiatric morbidity are subject to selection bias whenever they are conducted on clinical samples. This selection bias has a double origin. First, some bias arises from the fact that the probability of a couple being drawn for a clinical sample is dependent on whether one or both spouses are afflicted with the illness in question. A second source of bias lies in the likelihood that each spouse's help-seeking behavior is not independent of the other's. It would appear then that, owing to this selection bias, it is preferable to restrict the study of spouse similarity for psychiatric morbidity to general-population samples.

Family history of hypertension, gender, and cardiovascular responsivity during stress

The relationships of family history of hypertension and gender to cardiovascular responses to stress were investigated in this research. One hundred twenty-three subjects were monitored while they rested and performed two tasks, reaction time and Ravens progressive matrices. Positive-family history males exhibited higher levels of systolic blood pressure than the negative male group and higher levels of rate pressure product than the positive-family history female group. Positive-family history males also had heart rate levels as high as the females. Female subjects did not differ from each other based on family history. In addition, subjects were grouped by gender and by high- or low-heart rate reactivity. The results suggest that heart rate reactivity has equally broad effects on cardiovascular function for males and females; for males, this reactivity during rests and tasks also tends to be associated with family history of hypertension.

The nature/nurture controversy: spouse-likeness revisited

Within the past twelve months two distinguished scientific journals have once again raised the issue of nature versus nurture in health and sickness. The conclusion continues to be simply that both genetics and environment play a role. The issue still to be resolved is the relative contributions of nature and nurture. The model which most contributes to the answer is the very one least employed, namely spouse-likeness. This is a review of the approximately 100 most recent articles. It is evident that, within the limits of these observations, environment may play a more dominant role than generally considered.

Essential hypertension in blacks: epidemiology, characteristics, and possible roles of racial differences in sodium, potassium, and calcium regulation

Racial differences in the regulation of Na+, K+, and Ca2+ have been shown both at the systemic and cellular levels. These include a higher incidence of "salt sensitivity," lower urinary K+ excretion, lower plasma renin activity, and higher circulating levels of immunoreactive parathyroid hormone and 1.25 dihydroxyvitamin D in blacks than in whites. Blacks exhibit a higher erythrocyte Na+ concentration, coupled with a lower maximal initial reaction velocity of erythrocyte Na,K-ATPase. Blacks also appear to differ from whites in erythrocyte Na+, K+ cotransport and Na-Li countertransport. Moreover, they show a higher activity of the Na(+)-H+ antiport in skin fibroblasts and a greater response of cellular Ca2+ signaling to agonists in serum. Mechanisms linking some of these racial differences in ionic metabolism to the increased propensity of blacks to develop essential hypertension are proposed, and the epidemiology and characteristics of this disease in blacks are reviewed.

Genetics of primary hypertension

Geneticists seek to understand the interaction between genetic and environmental causes of phenotypic variation among individuals in a population. Clinical studies have established that an individual's blood pressure (BP) level is the consequence of the interaction of biologically determined characteristics of the nervous, renal, endocrine and circulatory systems with factors that define one's environment, such as dietary salt, stress and exercise. The many genes that orchestrate the development of these biologically determined characteristics are expected to determine one's BP level, one's increase in BP with age and one's BP response to changes in the environment. One consequence of such a multifactorial etiology is that there are multiple combinations of genetic and environmental factors that may lead to the same BP level. The prevention and control of hypertension will be enhanced when intervention strategies take into account this etiological heterogeneity in determining the hypertensive endpoint. We are pursuing a level crossing strategy in the study of the causes of interindividual BP differences. According to this approach relevant phenotypes that link genetic and environmental factors with blood pressure levels are identified, the genetic contribution to variability in these phenotypes is estimated and then the contribution of this genetic etiology to blood pressure variability is evaluated. We have successfully carried out such a level crossing approach in our investigations of the genetics of red cell sodium lithium countertransport and the relationship between sodium lithium countertransport and blood pressure. A single gene effect on red cell sodium lithium countertransport levels is the only single gene known to affect interindividual blood pressure variability.

Self-reported family history of hypertension in healthy middle-aged men

A self-reported first-degree family history of hypertension was obtained by questionnaire in two consecutive subsamples of middle-aged male attenders to a multi-phased health screening program in Malmö. This corresponded to 2739 men in lower (36-39 years) and 6597 in upper (46-48 years) middle age. Reported first-degree family history of hypertension was very frequent, about 26-27% in both groups. It was predominantly confined to the parental generation and was twice as common in mother as in father. Furthermore, the reported family histories showed marked interrelations. Thus, hypertension was much more frequently reported when both parents had the condition than if it only concerned one of them. It is proposed that these findings may reflect an increased awareness, investigation, diagnosis and treatment of hypertension rather than the genetic occurrence of the disease per se in modern society.

Behavioral response to induced conflict in families with a hypertensive father

To clarify the possible environmental mediation of familial aggregation of blood pressure (BP), we examined whether the behavior of family members differed between families with a hypertensive (n = 16) or a normotensive (n = 15) father. Three-member families consisting of a father, mother, and a boy or girl aged 8-13 years were videotaped as they interacted under standard conditions calling for disagreement or conflict. Their BPs were recorded before and after interactions. The videotaped material was reliably coded into behavioral categories by independent observers. The aggregate of all three members of families with hypertensive fathers, as well as normotensive mothers and the children in these families, showed significantly more negative nonverbal behavior than their counterparts in families with normotensive fathers.

Concordance for coronary risk factors among spouses

Values for several coronary risk factors, including systolic and diastolic blood pressure, serum cholesterol, triglycerides, blood glucose, uric acid, hemoglobin, weight, vitral capacity and cigarette smoking have been found to be similar among spouses in the Framingham Study. However, longitudinal analyses show that this spouse concordance does not increase over a twelve-year observation period, suggesting that it has arisen through the marriage of similar people rather than through the sharing of a common marital environment. Apparent conflicts between cross-sectional and longitudinal findings have been resolved by showing that spouses who were concordant at the begining of the study are more likely to survive to later exams, while discordant spouse pairs tend to be dissolved through the death of one of their members.

Genetics of obstetrical variables. A study from the collaborative perinatal project

Several obstetric variables were examined for genetic correlation in data from more than 8200 women (roughly 60 % black and 40 % white) linked into about 3200 family groups by birth or marriage and registered in the Collaborative Perinatal Project. Sister‐in‐law pairs yielded estimates of non‐genetic and spurious correlations which were generally absent or low. Pairs of sisters, mothers and daughters, half sisters, first cousins, and aunts and nieces were compared; such relatives were also compared in certain combinations of three. Familial correlation was present for age at menarche and durations of stages 1 and 3 of labor. None was found for gestation time of livebirths or for stage 2 of labor. A significant sister correlation for diagonal conjugate (size of pelvic inlet) was apparent in the white, but not the black, sample.

No families had two or more occurrences of the infrequent conditions: thrombosis, infertility diagnosis, incompetent cervix, leiomyoma, hyperemesis gravidarum, hydramnios, placenta praevia, or prolapsed cord. Familial correlation was significant for fetal death risk, but not for bleeding during pregnancy, abnormal presentation of the fetus, abruptio placentae, breast abnormalities and hypertension. Familial associations for anemia, postpartum hemorrhage, varicose veins and albuminuria were significant in the black data, but not in the smaller white sample. There was a positive, but non‐significant, association of toxemia in sisters.