Demographic, dietary, life style, and anthropometric correlates of blood pressure

Cardiometabolic health during early adulthood and risk of miscarriage: a prospective study

Background: Several studies have found that women who are overweight or obese have an increased risk of miscarriage. There is also some evidence of associations of other aspects of cardiometabolic health, including blood pressure and lipids, with miscarriage risk, although these have not been examined to the same extent as body-mass index (BMI). Methods: Our objective was to investigate the risk of miscarriage according to pre-pregnancy cardiometabolic health. We examined pre-pregnancy levels of BMI, blood pressure, fasting insulin and metabolites profile at age 18 and risk of miscarriage by age 24. The study included adult female offspring in the Avon Longitudinal Study of Parents and Children with a pregnancy between 18 and 24 years of age (n=434 for BMI and blood pressure; n=265 for metabolites). We used log-binomial regression to calculate adjusted associations between cardiometabolic health measures and miscarriage. Results: The overall risk of miscarriage was 22%.  The adjusted relative risks for miscarriage were 0.96 (95% CI: 0.92-1.00) for BMI (per unit increase), 0.98 (0.96-1.00) for systolic blood pressure, and 1.00 (0.97-1.04) for diastolic blood pressure (per 1 mmHg increase).  Total cholesterol, total lipids and phospholipids in HDL-cholesterol were associated with increased likelihood of miscarriage, but none of the p-values for the metabolites were below the corrected threshold for multiple testing (p-value ≤0.003). Conclusions: Our findings indicate no strong evidence to support a relationship between pre-pregnancy cardiometabolic health and risk of miscarriage in young, healthy women who became pregnant before age 24. Future studies are necessary that are able to evaluate this question in samples with a wider age range.

Cardiometabolic health during early adulthood and risk of miscarriage: a prospective study

Background: Several studies have found that women who are overweight or obese have an increased risk of miscarriage. There is also some evidence of associations of other aspects of cardiometabolic health, including blood pressure and lipids, with miscarriage risk, although these have not been examined to the same extent as body-mass index (BMI). Methods: Our objective was to investigate the risk of miscarriage according to pre-pregnancy cardiometabolic health. We examined pre-pregnancy levels of BMI, blood pressure, fasting insulin and metabolites profile at age 18 and risk of miscarriage by age 24. The study included adult female offspring in the Avon Longitudinal Study of Parents and Children with a pregnancy between 18 and 24 years of age (n=434 for BMI and blood pressure; n=265 for metabolites). We used log-binomial regression to calculate adjusted associations between cardiometabolic health measures and miscarriage. Results: The overall risk of miscarriage was 22%.  The adjusted relative risks for miscarriage were 0.96 (95% CI: 0.92-1.00) for BMI (per unit increase), 0.98 (0.96-1.00) for systolic blood pressure, and 1.00 (0.97-1.04) for diastolic blood pressure (per 1 mmHg increase).  Total cholesterol, total lipids and phospholipids in HDL-cholesterol were associated with increased likelihood of miscarriage, but none of the p-values for the metabolites were below the corrected threshold for multiple testing (p-value ≤0.003). Conclusions: Pre-pregnancy cardiometabolic health in late adolescence was not associated with miscarriage risk in young, healthy women who became pregnant before age 24.

The molecular basis of blood pressure variation

Advances in genetic mapping and sequencing techniques have led to substantial progress in the study of rare monogenic (Mendelian) forms of abnormal blood pressure. Many disease-defining pathways for hypertension have been identified in the past two decades. Perturbations in renal salt handling appear to be a common mechanism underlying these rare syndromes of hypertension. Excess activation at various points in the mineralocorticoid signaling pathway and malfunctioning of the autonomic (specifically sympathetic) nervous system have both been implicated in inducing hypertension, while complementary studies examining low blood pressure phenotypes have identified novel pathways exclusively linked to renal salt wasting in either the thick ascending limb or the distal nephron. The genetic defects and the physiological and cellular pathways affected in these various disorders are reviewed here. Importantly, studies have suggested that genetic variation affecting these same genes and pathways may play an important role in explaining the variation of blood pressure levels in the general population. The investigation of rare syndromes of human blood pressure variation has important implications for improving the diagnosis and treatment of hypertension.

Lack of an association between TSC gene Arg904Gln polymorphisms and essential hypertension risk based on a meta-analysis

Although there have been several studies investigating a possible association between essential hypertension and TSC gene Arg904Gln polymorphisms, the results have been inconsistent. We conducted a meta-analysis of four case-control studies (one study in Europe and three studies in Asia), including 1811 essential hypertension cases and 1381 controls. The pooled results showed no significant associations between any of these polymorphisms and essential hypertension (allele Arg vs allele Gln: odds ratio (OR) = 0.94, 95% confidence interval (95%CI) = 0.70-1.27), additive genetic model (Arg/Arg vs Gln/Gln: OR = 0.98, 95%CI = 0.43-2.23), dominant genetic model (Arg/Arg + Arg/Gln vs Gln/ Gln: OR = 0.97, 95%CI = 0.43-2.21), and recessive genetic model (Arg/ Arg vs Arg/Gln + Gln/Gln: OR = 1.03, 95%CI = 0.45-2.35). Based on the results of our meta-analysis, we conclude that the TSC gene Arg904Gln polymorphism is not associated with essential hypertension risk.

G2736A polymorphism of thiazide-sensitive Na-Cl cotransporter gene predisposes to hypertension in young women

OBJECTIVE

The thiazide-sensitive Na-Cl cotransporter (TSC) is located in the distal renal tubules. Several mutations of the TSC gene cause Gitelman's syndrome, which is an autosomal recessive disease characterized by low blood pressure and hypokalemia. Recently, an association between TSC gene polymorphisms (Arg904Gln, G2736A; Thr465Thr, C1420T; Gly264Ala, G816C) and essential hypertension has been reported in Sweden. We examined the genetic involvement of the TSC gene in essential hypertension in Japanese.

DESIGN

Participants were recruited from outpatients of Osaka University Hospital. We investigated 386 hypertensive and 371 normotensive subjects.

METHODS

Genotypes of TSC polymorphisms (G2736A, C1420T, G816C) were determined by the TaqMan polymerase chain reaction (PCR) method, and statistical significance was examined using JMP 5.0.1J (SAS Institute Inc., Cary, North Carolina, USA). The allele frequency of A2736 and T1420 was 6.0 and 3.0%, respectively, whereas we could not detect the G816C polymorphism in this study. Only the G2736A polymorphism was significantly associated with the prevalence of hypertension (P <0.04), and the estimated odds ratio was 1.8 (95% confidence interval, 1.1-3.0) in A2736 allele carriers. The odds ratio for hypertension in A2736 carriers was increased to 2.2 (1.1-4.9) in women (n=413), and further to 3.3 (1.4-8.0) in women with early onset of hypertension (< or = 50 years old). In addition, all subjects with the homozygous A2736 allele in this study (n=2) and the Swedish study (n=5) were hypertensive.

CONCLUSION

G2736A polymorphism of the TSC gene is a genetic predisposing factor for essential hypertension in Japanese women.

Blood pressure and hypertension in middle-aged women in relation to weight and length at birth: a follow-up study

OBJECTIVES

To examine the relationship between indicators at birth and adult blood pressure and risk for developing hypertension at two age levels.

DESIGN

Original midwife records of 438 women born at term participating in a prospective population study in Göteborg, Sweden with blood pressure and hypertension assessment at both 50 and 60 years of age.

RESULTS

Systolic blood pressure at both age levels showed a U-shaped relationship to weight and length at birth. Hypertension prevalence at 60 years was significantly and inversely related to both weight and length at birth, but not at 50 years. Significantly higher risk for hypertension was found in the lowest birth weight quintile [odds ratio (OR) = 2.0, 95% confidence interval (CI) 1.1-3.8] and lowest birth length tertile (OR = 1.8, 95% CI 1.1-3.0), in relation to the middle quintile/tertile, with or without adjustment for adult body size (as body mass index), at 60 years but not at 50 years. At 50 years, hypertension risk decreased by 3% (95% CI 0.92-1.01) for every 100 g increase in birth weight and 6% (95% CI 0.83-1.05) per cm birth length. At age 60 years, hypertension risk decreased by 4% (95% CI 0.92-0.99) per 100 g birth weight and 10% (95% CI 0.81-0.99) per cm length.

CONCLUSIONS

Size at birth was a predictor of hypertension risk in women at 60 years but not 50 years. This study supports the hypothesis that poor fetal growth, as measured by low weight or length at birth, may contribute to the development of hypertension in later life and that this relationship became stronger with age.

Insulin and hypertension in the NHLBI Family Heart Study: a sibpair approach to a controversial issue

The association between insulin and hypertension remains equivocal. We therefore investigated insulin levels in 3037 normotensive and 1067 hypertensive subjects from the National Heart, Lung and Blood Institute (NHLBI) Family Heart Study (FHS) by two different approaches. First, we compared insulin levels between normotensive and 275 untreated hypertensive subjects. Insulin levels unadjusted as well as adjusted for age, sex, and center were significantly higher in hypertensives. After adjustment for body mass index (BMI), insulin remained significantly higher only in the diastolic hypertensive group (mean +/- SD 77.0 +/-36.7 pmol/L, P < .01) but not in the isolated systolic hypertensive group (67.0 +/- 38.2 pmol/L) when compared to normotensives (63.2 +/- 29.1 pmol/L). A sibpair analysis was then used that compared the intra-sibpair differences in insulin concentrations to the intra-sibpair differences in blood pressure (BP) levels. This approach was intended to control for the effects of genetic and residual shared environmental variance upon insulin levels. The intra-sibpair difference in insulin concentrations between concordant (diastolic and systolic deltaBP < 5 mm Hg) and discordant sibpairs (diastolic and systolic deltaBP > 15 and > 20 mm Hg, respectively) was no longer significantly different when adjusted for BMI (2.7 v 5.9 pmol/L for diastolic and -1.7 v -1.8 pmol/L for systolic BP). Even the random selection of one sibpair from each of the 326 families independently of insulin and BP levels did not result in a significant correlation between the intrasibpair differences in insulin and BP. Using an insulin resistance index instead of insulin did not change our findings. Our investigation in the FHS sample of families suggests that there is only a small, if any, influence of insulin levels on BP after adjustment for obesity-related sources of variation.

Some coronary risk factors related to the insulin resistance syndrome and treatment with gemfibrozil. Experience from the Helsinki Heart Study

BACKGROUND

Coronary risk factors related to the insulin resistance syndrome tend to cluster in the same individual. Our previous studies have shown that the dyslipidemia characteristic of this syndrome--low HDL cholesterol and high triglyceride (TG) levels--responds well to treatment with gemfibrozil. Most factors related to insulin-resistance syndrome decrease fibrinolytic capacity, whereas a recent study showed that gemfibrozil improves it and thus may attenuate thrombotic events. To discover whether subjects with clustering of factors related to this resistance might in particular benefit from gemfibrozil, we reanalyzed the Helsinki Heart Study data.

METHODS AND RESULTS

We used Cox regression models to explore the effects of gemfibrozil among overweight subjects with additional coronary risk factors in this hypercholesterolemic male population of 2046 subjects randomized to gemfibrozil and 2035 to placebo. The effect of gemfibrozil was largely confined to overweight subjects: among those with body mass index (BMI) > 26 kg/m2, the net difference in cardiac end points between gemfibrozil and placebo groups was 21 (25 of 1119 versus 46 of 1081), and in those with BMI < or = 26 kg/m2, it was 7 (31 of 927 versus 38 of 954). The risk reduction with gemfibrozil was 78% (P = .002) among those with BMI > 26 kg/m2 and dyslipidemia (TG > or = 2.3 mmol/L and HDL cholesterol < 1.08 mmol/L). Among those with BMI > 26 kg/m2 and three or four of the following factors present--smoking, sedentary lifestyle, blood pressure > or = 140/90 mm Hg, or blood glucose > 4.4 mmol/L--the risk reduction was 68% (P = .03).

CONCLUSIONS

Gemfibrozil reduced the coronary risk mainly in overweight subjects with additional risk factors known to contribute to the insulin-resistance syndrome or predispose to it.

Correlates of blood pressure in Seventh-Day Adventist (SDA) and non-SDA adolescents

OBJECTIVE

This comparative study was designed to discover early determinants of systolic (S) and diastolic (D) blood pressure (BP) elevations in 138 Seventh-Day Adventist (SDA) and 89 non-SDA male and female adolescents (median age, 17 years) living at three residential secondary schools in North Carolina.

METHODS

Measurements were made of blood pressure, body weight, and height, and information was collected on lifestyle factors, dietary intake, and other behaviors, including exercise, religiosity, Type A behavior, and anger, by questionnaire. Multiple stepwise regression analyses were performed with BP, either SBP or DBP, as the independent variable.

RESULTS

A significant direct association was found only between body weight and BP, but weak associations were shown between BP and other variables, including exercise, diet, religiosity, Type A behavior, and anger. Male and female SDA students showed significantly higher SBPs and DBPs than did non-SDA adolescents though the differences were small (approximately 5 mm for each sex).

CONCLUSIONS

These findings suggest that the higher BP values of SDA adolescents, who were all practicing lacto-ovo-vegetarians, compared to similarly aged health-conscious non-SDAs, are determined more by eating behaviors that contribute to gains in body weight than by any other lifestyle variable. Furthermore, these data support the notion that the BP-protective effects of the vegetarian diet may not emerge in these SDA youth until early adulthood.

Correlations between education and arthritis in the 1971-1975 NHANES I

Data from the National Health and Nutrition Examination Survey I, 1971-1975 (NHANES I) were used to analyze associations among highest education level and arthritis. The dependent variables indicated whether the respondent had ever been diagnosed with any form of arthritis by a physician (10,678 women and 7243 men) or whether physician X-ray readings suggested arthritis of the knee (3491 women and 3119 men). These variables did not distinguish between osteo- and rheumatoid arthritis. It is likely that the great majority of the sample reporting or diagnosed with arthritis had osteoarthritis. There were strong univariate correlations between answers to the general arthritis question and the knee question on the one hand and gender, age, body mass, schooling, income and employment on the other. Respondents' education level was found to be strongly and negatively associated with self-reported arthritis in the larger samples both before and after controls were entered for employment, income and potential biological risk factors. The association between self-reported arthritis or arthritis of the knees and education was weaker for men, but not for women after employment and income were accounted for. When body mass was accounted for, the association between self-reported arthritis or arthritis of the knees and education was weaker among women but not men. Long-run preventive strategies to combat osteoarthritis ought to consider investments in education.

Can anti-oxidants prevent ischaemic heart disease?

Ischaemic heart disease remains a major cause of mortality in developed countries. A number of important risk factors for the development of coronary atherosclerosis have been identified including hypertension, hypercholesterolaemia, insulin resistance and smoking. However, these factors can only partly explain variations in the incidence of ischaemic heart disease either between populations or within populations over time. In addition, population interventions based upon these factors have had little impact in the primary prevention of heart disease. Recent evidence suggests that one of the important mechanisms predisposing to the development of atherosclerosis is oxidation of the cholesterol-rich low-density lipoprotein particle. This modification accelerates its uptake into macrophages, thereby leading to the formation of the cholesterol-laden 'foam cell'. In vitro, low-density lipoprotein oxidation can be prevented by naturally occurring anti-oxidants such as vitamin C, vitamin E and beta-carotene. This article explores the evidence that these dietary anti-oxidants may influence the rate of progression of coronary atherosclerosis in vivo and discusses the need for formal clinical trials of anti-oxidant therapy.

Risk factors for hypertension in a national cohort study

Hypertension continues to be a major public health problem in the United States. We used data from the National Health and Nutrition Examination Survey Epidemiologic Followup Study (1971-1984) to examine predictors of hypertension for the 7,073 participants free from hypertension at the baseline examination. The follow-up period averaged 10 years. Body mass index was positively related to the probability of hypertension developing among white men (n = 2,370), white women (n = 3,949), black men (n = 231), and black women (n = 523). Education was inversely associated with the probability of hypertension developing among white women and was of borderline significance among white men and black women. In a subanalysis of white men (n = 1,790) and white women (n = 3,063) who completed the 24-hour recall dietary questionnaire, dietary consumption of sodium, calcium, and potassium did not predict the development of hypertension. The failure of our study to support findings relating intake of dietary cations to the development of hypertension may be attributable to imprecision in the measurement of dietary data and misclassification of hypertension status. These data reinforce the importance of weight control in the primary prevention of hypertension.

Epidemiologic studies utilizing surveys: accounting for the sampling design

BACKGROUND

Since large-scale health surveys usually have complicated sampling schemes, there is often a question as to whether the sampling design must be considered in the analysis of the data. A recent disagreement concerning the analysis of a body iron stores-cancer association found in the first National Health and Nutrition Examination Survey and its follow-up is used to highlight the issues.

METHODS

We explain and illustrate the importance of two aspects of the sampling design: clustering and weighting of observations. The body iron stores-cancer data are reanalyzed by utilizing or ignoring various aspects of the sampling design. Simple formulas are given to describe how using the sampling design of a survey in the analysis will affect the conclusions of that analysis.

RESULTS

The different analyses of the body iron stores-cancer data lead to very different conclusions. Application of the simple formulas suggests that utilization of the sample clustering in the analysis is appropriate, but that a standard utilization of the sample weights leads to an uninformative analysis. The recommended analysis incorporates the sampling weights in a nonstandard way and the sample clustering in the standard way.

CONCLUSIONS

Which particular aspects of the sampling design to use in the analysis of complex survey data and how to use them depend on certain features of the design. We give some guidelines for when to use the sample clustering and sample weights in the analysis.

Relation of electrolytes to blood pressure in men. The Yi people study

The relations of sodium, potassium, calcium, and magnesium to blood pressure were investigated in four groups of men (119 high-mountain Yi farmers, 114 mountainside Yi farmers, 89 Yi migrants, and 97 Han people) with a wide range of electrolyte intake in Puge County, Sichuan Province, People's Republic of China. Electrolytes were measured in diet, serum, and urine. Sodium excretion was 73.9 mmol/24 hr in high-mountain Yi farmers, 117.9 mmol/24 hr in mountainside Yi farmers, 159.4 mmol/24 hr in Yi migrants, and 186.0 mmol/24 hr in the Han people. In ecological correlation analysis, dietary and urinary sodium were significantly and positively correlated with both systolic and diastolic pressure, whereas serum sodium showed no relation with blood pressure. In diet, serum, and urine, potassium was negatively related to systolic and diastolic pressure, whereas the sodium/potassium ratio showed a positive association. With regard to calcium, only urinary excretion was significantly and positively related to blood pressure. No relation was found between magnesium and blood pressure. Analyses at the individual level confirmed the results for sodium and potassium seen at the ecological level, but in addition, dietary calcium and magnesium were significantly and negatively correlated to both systolic and diastolic pressure, and urinary magnesium was inversely related to diastolic pressure. These relations persisted after controlling for age, body mass index (kg/m2), heart rate, alcohol, and total energy intake in multiple regression analysis performed separately for electrolytes in diet, serum, and urine. In multiple regression analysis, an increase in sodium intake of 100 mmol/day corresponded to an increase of 2.3 mm Hg systolic blood pressure and 1/8 mm Hg diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of fat mass and fat distribution to blood pressure

The relationship of fat mass, lean body mass (LBM), and fat distribution to blood pressure was examined in Japanese adult men and women. Percent body fat was estimated using two skinfold thicknesses, and fat mass and LBM were then calculated. Correlation coefficients showed that fat mass, fat distribution, and age were weakly associated with blood pressure levels, and that the correlation coefficients of LBM to blood pressure levels were nearly zero. Stepwise regression analysis revealed that fat mass and age contributed significantly to the variations in blood pressure levels. In addition, only in the case of men, trunk-extremity skinfolds ratio was also entered into the model for diastolic and mean arterial blood pressure. It thus has been concluded that fat mass may be the more predictive determinant of blood pressure level than LBM in the Japanese population, and that the independent correlation of fat distribution to blood pressure is rather small.

Nutrient intake and blood pressure: families of adult identical twins

To investigate the relationship of dietary intake to blood pressure, 198 adults and 53 children who were members of 92 nuclear families completed a 3-day diet diary prior to an outpatient clinic examination for cardiovascular disease risk factors. Nutrient intake was significantly related to age and anthropometric variables in adults. Sodium and potassium intake were related to blood pressure in adults, but this relationship was no longer significant after adjustment for caloric intake. The diet and blood pressure relationships in children were less clear. Multiple linear regression techniques using age, anthropometric variables, and nutrient intake demonstrated that in adults age and skinfold were the principal determinants of blood pressure, but in children age and saturated fat intake were most likely to enter the equations. In comparisons of normotensive and hypertensive adults, there were no differences in the dietary intakes of these electrolytes. The results of this investigation underscore the complex interaction of nutrient intake with body size and age. Investigators who focus only on a few nutrients and fail to account for other sources of variation can be misled.

Age and blood pressure changes. A 20-year follow-up study in nuns in a secluded order

In a prospective study, 144 white nuns belonging to a secluded monastic order and 138 white control laywomen were followed for 20 years to investigate whether living for a long time in a stress-free environment influences the effect of aging on blood pressure. Silence, meditation, and isolation from society are the distinctive features of the life-style examined. At study entry, blood pressure was not dissimilar in the nuns and the control group, but it increased over time only in the controls, with a mean slope of the regression line (beta coefficient) of 0.089 in the nuns (NS) and 2.171 in the controls (p less than 0.0001) for systolic blood pressure and of 0.054 in the nuns (NS) and 0.742 in the controls (p less than 0.0001) for diastolic blood pressure. Weight and body mass index increased similarly over time in the two groups. Family history of hypertension was not dissimilar between the groups. Serum cholesterol and triglycerides, higher at study entry in the nuns, increased similarly over time in the two groups. Twenty-four-hour urinary sodium excretion, collected randomly in both groups, did not differ over time between nuns and controls. None of the women smoked or used oral contraceptives. Educational level was higher in the control group, but subgroups of 48 nuns and 52 laywomen of comparable educational level maintained the same difference in the blood pressure trend over time as in the main cohort. Parity affected the increase of systolic, but not of diastolic, blood pressure with age among the laywomen, but nuns and no-childbirth controls maintained a significantly different blood pressure trend over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Examining neighbourhood confounding in a survey: an example using the National Health and Nutrition Examination Survey II

This paper demonstrates a methodology for examining whether neighbourhood stratification lessens the confounding bias of some specific risk-factor/disease associations in analysis of the National Health and Nutrition Examination Survey II (NHANES II). The fortuitous clustering of the sample design of NHANES allows us to estimate risk-factor/disease associations with and without controlling for neighbourhood effects on the same population. We briefly discuss the implications of this methodology for neighbourhood matching in case-control studies.

Correlates of systolic and diastolic blood pressure in men 40 to 59 years of age sampled from United States of America and Union of Soviet Socialist Republics Lipid Research Clinics populations

The correlates of blood pressure (BP) were investigated in 2 samples using common protocols, one from a Union of Soviet Socialist Republics study in 2 locations and one from a United States of America study in 9 locations. Age, heart rate, Quetelet index, high density lipoprotein cholesterol, natural logarithm of triglycerides and fasting glucose were positively related to systolic BP in both samples. In diastolic BP, alcohol consumption, heart rate, Quetelet index and natural logarithm of triglycerides were positively associated, and number of cigarettes smoked was negatively related in both samples.

Sodium sensitivity: a determinant of essential hypertension

The epidemiologic correlation of chronic dietary salt intake among populations with the prevalence of hypertension has resulted in the concept that sodium plays an etiologic role in the development of essential hypertension (EH). However, the association of sodium intake with blood pressure in individuals within populations has been difficult to demonstrate. The differing human responses to sodium intake are dependent upon the individual level of sodium sensitivity or sodium resistance. Factors associated with sodium sensitivity are race, age, and other dietary factors. More recent investigations have pursued the interaction of sodium intake with other physiologic parameters including neurogenic activity, vascular structure, renal function, and other cations such as potassium and calcium. The observations that some humans demonstrate very little increase in blood pressure despite high levels of sodium intake supports the concept that a high sodium intake alone is not a single causal factor in hypertension. Sodium intake appears to interact with renal excretory capacity and vascular compliance. These varying physiologic functions must be delineated to characterize sodium sensitivity.

The association between blood pressure, age, and dietary sodium and potassium: a population study

We examined the relationship between blood pressure and dietary sodium and potassium intake estimated from 24 hr diet recall in a population of 584 men and 718 women 30 to 79 years old in Southern California. In men, but not women, age-adjusted systolic and diastolic blood pressure correlated significantly with dietary sodium intake. In both men and women, age-adjusted diastolic blood pressure significantly inversely correlated with dietary potassium intake. Age-adjusted systolic and diastolic blood pressure correlated significantly with the dietary sodium/potassium ratio in each sex; correlations were better for the ratio than for either sodium or potassium alone. The relationship was apparent over the whole range of blood pressure and dietary intake. A marked age gradient was apparent in men, the regression slope for blood pressure vs sodium/potassium ratio increasing with increasing age, suggesting increasing sensitivity to dietary sodium/potassium ratio with age. Adjusting for intake of other dietary variables, including calories, protein, carbohydrate, saturated fat, alcohol, calcium, and fiber, did not alter the relationships; adjusting for body mass index reduced the strength of the association in women but not in men. These results support the hypothesis that dietary sodium and potassium are related to blood pressure within a population.

Double-blind, placebo-controlled trial of potassium chloride in the treatment of mild hypertension

Epidemiological and experimental data suggest blood pressure-lowering effects of dietary potassium. A randomized, double-blind clinical trial was used to assess blood pressure response to orally administered potassium, 120 mEq/day, and to placebo in 101 adults with mild hypertension. Blood pressure was measured with a random-zero sphygmomanometer every 2 weeks of this 8-week trial. Systolic blood pressure in the potassium-treated group decreased by 6.4 +/- 13.7 (SD) mm Hg (p less than or equal to 0.025) compared with 0.11 +/- 13.0 mm Hg in the placebo-treated group (p = 0.96). Diastolic blood pressure in the potassium-treated group decreased by 4.1 +/- 8.3 mm Hg (p less than or equal to 0.05) compared with a 1.6 +/- 6.5 mm Hg decrease in placebo-treated subjects (p = 0.09). Baseline blood pressure of potassium-treated subjects was unexpectedly higher than that of controls. After correcting for baseline variation, blood pressure still decreased 3.4/1.8 mm Hg more in potassium recipients than in placebo recipients (p = 0.14 and 0.24, respectively). Blood pressure decreased by 19/13 mm Hg in five blacks taking potassium versus a 1/0 mm Hg increase in seven blacks taking placebo. Compliance with the potassium regimen was 91.5% by pill count; only one subject discontinued treatment because of side effects. In conclusion, 120 mEq/day of microencapsulated potassium chloride was well tolerated in adults with mild hypertension. An antihypertensive effect of potassium cannot be ruled out despite the fact that there was no statistically significant difference between potassium-treated and placebo-treated subjects after adjustment for differences in baseline blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Body fat patterning and blood pressure in children and young adults. The Bogalusa Heart Study

The relationship of central body fat (measured by subscapular skinfold) and peripheral body fat (measured by triceps skinfold) to blood pressure was investigated in 3784 subjects aged 5 to 24 years old from the biracial community of Bogalusa, Louisiana. After adjustment for height, age, sex, and race, significant relationships were found for both central body fat (r = 0.19 and 0.14, p less than 0.0001) and peripheral body fat (r = 0.15 and 0.12; p less than 0.0001) with systolic and diastolic (fourth phase) blood pressure, respectively. However, the relationship between peripheral body fat and blood pressure, after controlling for the level of central body fat, was negligible (r = 0.00 and 0.01 for systolic and diastolic blood pressure, respectively). In contrast, the central body fat-blood pressure relationship remained statistically significant even after controlling for the peripheral body fat level. For central body fat, the partial correlations with systolic blood pressure were highest in young children (r = 0.15), dropped slightly during adolescence (r = 0.12), and became nonsignificant only in 18- to 24-year-old female subjects; correlations remained high in both black and white 18- to 24-year-old male subjects (r = 0.18 and 0.16, respectively). Mean levels of systolic blood pressure from the lowest to the highest quartile of central body fat ranged from 100.4 to 108.9 mm Hg. The adult hypertension-central body fat relationship, which has been shown by others, appears to exist in children. Continued efforts at early identification and prevention of obesity in children are warranted.

The relative contribution of body fat and fat pattern to blood pressure level

Although the association between body weight and blood pressure is irrefutable, body fat mass and blood pressure level may not necessarily be directly related. To clarify the relative contribution of fat mass to blood pressure level, we analyzed data on 399 adults consecutively entering a weight control program. Although most subjects were notably overweight (mean ideal body weight 177%), the population represented a wide spectrum of body weights and blood pressure levels. Study parameters included body fat mass (by total body water, 40K, and Steinkamp formula), lean body mass, body build (chest to height ratio), fat cell number and size from bilateral buttock biopsy specimens, upper fat pattern by arm to thigh circumference ratio, and central fat pattern by subscapular to triceps skinfold ratio. Our results concurred with previously noted correlations between obesity and blood pressure (as mean arterial pressure): weight (r = 0.44), percentage of body fat (r = 0.19), and absolute fat mass (r = 0.38; all p less than 0.01); however, lean body mass, age, and body build correlated highly with both fat mass and mean arterial pressure, thereby confounding this relationship. Multivariate analysis was performed to evaluate the relative contribution of fat mass to mean arterial pressure in the presence of these and other potentially confounding variables. Lean body mass, age, body build, and an upper body fat pattern were found to contribute significantly to the variation in mean arterial pressure (p less than 0.01). In their presence, percentage of body fat, absolute fat mass, central fat pattern, fat cell characteristics, and age of onset of obesity did not significantly improve the predictability of mean arterial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Diet, blood pressure, and multicollinearity

Recent reports of an inverse association between dietary calcium intake and hypertension stimulated this analysis of the relationship of blood pressure to more than 20 dietary factors among a group of 8000 Japanese men in Hawaii. Reported intakes of potassium, calcium, protein, and milk were all inversely associated with blood pressure levels when examined one at a time while controlling for other risk factors. Alcohol intake was directly associated with blood pressure, and was treated as a confounding variable in the analysis. The association of potassium intake with blood pressure was relatively stronger than the associations for other nutrients, but the intake of potassium was so highly correlated with intakes of calcium, milk, and protein that it was not statistically possible to identify the independent association of potassium and blood pressure. Calcium intake was strongly correlated with milk and potassium intakes, and only calcium from dairy sources was associated with blood pressure. These data thus indicate that several dietary factors are inversely related to blood pressure levels independently of other risk factors such as age, body mass, and alcohol intake. The high degree of intercorrelation (multicollinearity) among these dietary factors, however, indicates that the independent role of any specific nutrient cannot be conclusively separated from the possible effects of other nutrients in this type of study.

Milk consumption, calcium intake, and decreased hypertension in Puerto Rico. Puerto Rico Heart Health Program study

The baseline observations in the Puerto Rico Heart Health Program during 1965-1968 involved blood pressure determinations, other measurements, and a 24-hour dietary recall in 7932 men aged 45-64 years. This extensive data base provided an opportunity to test the hypothesis that low calcium intake is related to increased blood pressure level. Among men without baseline coronary heart disease and not taking antihypertensive medication, there was an inverse relationship between milk consumption and definite hypertension in urban Puerto Rican men and older rural men. When data from all age and area groups had been averaged, a twofold increase in hypertension was found in subgroups who drank no milk compared to those who consumed over 1 quart of milk a day. Similar trends were found when an estimate of total calcium intake from food, principally from milk, was used. With multivariate analysis while known correlates of blood pressure were simultaneously considered, an independent effect persisted between milk consumption and blood pressure. These results appeared to confirm an inverse association between calcium and hypertension. It was still not possible to ascribe a causal relationship between calcium and blood pressure, however, due to the intricate network of covarying food intakes, the factors related to absorption or lack of absorption of calcium, and the possible role that unmeasured social and cultural factors may play in the observed relations.