Hyponatremia in the general population. What does it mean?

Hyponatremia is a frequent problem in clinical practice and is known to be associated with a variety of serious adverse outcomes. Estimates from the US general population and several community-based cohorts indicate that hyponatremia is also relatively common in these settings, especially among seniors, individuals with underlying disease, and those taking a variety of prescription medications. Prevalence is greatly increased when persons with a "low normal" level of serum sodium are considered. Population-based studies have identified a U-shaped relationship between serum sodium and all-cause mortality, with the increased risk at the lower end of the distribution being seen in persons with a "low normal" level of serum sodium as well as those meeting the traditional definition of hyponatremia. The hyponatremia associated risk in epidemiologic studies is of lesser magnitude than in hospital-based studies but of great potential importance give the much larger number of persons with a low serum sodium in the general population. An important challenge for the research community is to determine whether low levels of serum sodium are a direct cause of increased risk. Population-based studies are likely to provide the best opportunity to resolve this question.

A randomized controlled trial of dietary fiber intake on serum lipids.

OBJECTIVE: Clinical trials have indicated that water-soluble fiber from oats reduces serum cholesterol among hypercholesterolemic patients on a low-fat diet. We examined the effect of dietary fiber intake on serum lipids among persons without hypercholesterolemia. DESIGN: Randomized controlled trial. SETTING AND SUBJECTS: We recruited 110 participants who were aged 30-65 years and had a serum cholesterol level < 240 mg/dl from community. INTERVENTION: Study participants were randomly assigned to receive 8 g per day of water-soluble fiber from oat bran or a control intervention. RESULTS: At baseline, the mean levels of serum cholesterol and other measured variables were comparable between the high-fiber and control groups. Over the 3-month intervention, mean changes (95% confidence interval (CI)) in total, HDL-, and LDL-cholesterol were -2.42 mg/dl (-8.90 to 4.05 mg/dl; P = 0.46), -0.24 mg/dl (-2.19 to 1.71 mg/dl; P = 0.81), and -1.96 mg/dl (-7.32 to 3.40 mg/dl; P = 0.47) in the fiber group and -0.02 mg/dl (-5.29 to 5.26 mg/dl; P = 0.99), 1.42 mg/dl (-0.74 to 3.59 mg/dl; P = 0.19), and -0.64 mg/dl (-5.30 to 4.03 mg/dl; P = 0.79) in the control group, respectively. The net changes (95% confidence interval) in total, HDL-, and LDL-cholesterol were -2.40 mg/dl (-10.6 to 5.81 mg/dl; P = 0.56), -1.66 mg/dl (-4.55 to 1.22 mg/dl; P = 0.26) and -1.33 mg/dl (-8.33 to 5.68 mg/dl; P = 0.71), respectively. CONCLUSIONS: Our study does not support the hypothesis that water-soluble fiber intake from oat bran reduces total and LDL-cholesterol in study participants with a normal serum cholesterol level.

Dose-response of sodium excretion and blood pressure change among overweight, nonhypertensive adults in a 3-year dietary intervention study.

A cross-sectional dose-response relationship between sodium intake and blood pressure (BP) has been demonstrated, but evidence for a graded longitudinal effect is limited. Evaluation of BP response to sodium reduction was assessed in a 3-year lifestyle dietary intervention trial. BP changes at 18 and 36 months after enrollment were analysed according to concurrent quantitative changes in sodium excretion and by categories of success in sodium reduction among 1157 men and women, ages 30-54 years, with a diastolic BP (DBP) 83-89 mmHg, systolic BP (SBP) <140 mmHg, body weight 110-165% of sex-specific standard weight, and valid baseline urinary sodium excretion. Participants were randomized to a Sodium Reduction intervention (n=581) or Usual Care (n=576). From a 187 mmol/24 h baseline mean sodium excretion, net decreases were 44 mmol/24 h at 18 months and 38 mmol/24 h at 36 months in Sodium Reduction vs Usual Care. Corresponding net decreases in SBP/DBP were 2.0/1.4 mmHg at 18 months, and 1.7/0.9 mmHg at 36 months. Significant dose-response trends in BP change over quintiles of achieved sodium excretion were seen at both 18 (SBP and DBP) and 36 (SBP only) months; effects appeared stronger among those maintaining sodium reduction. Estimated SBP decreases per 100 mmol/24 h reduction in sodium excretion at 18 and 36 months were 2.2 and 1.3 mmHg before and 7.0 and 3.6 mmHg after correction for measurement error, respectively. DBP changes were smaller and nonsignificant at 36 months. In conclusion, incremental decreases in BP with lower sodium excretion were observed in these overweight nonhypertensive individuals.

Sodium reduction for hypertension prevention in overweight adults: further results from the Trials of Hypertension Prevention Phase II.

Sodium reduction is efficacious for primary prevention of hypertension, but the feasibility of achieving this effect is unclear. The objective of the paper is detailed analyses of adherence to and effects of the sodium reduction intervention among overweight adults in the Trials of Hypertension Prevention, Phase II. Sodium reduction (comprehensive education and counselling about how to reduce sodium intake) was tested vs no dietary intervention (usual care) for 36-48 months. A total of 956 white and 203 black adults, ages 30-54 years, with diastolic blood pressure 83-89 mmHg, systolic blood pressure (SBP) <140 mmHg, and body weight 110-165% of gender-specific standard weight were included in the study. At 36 months, urinary sodium excretion was 40.4 mmol/24 h (24.4%) lower in sodium reduction compared to usual care participants (P<0.0001), but only 21% of sodium reduction participants achieved the targeted level of sodium excretion below 80 mmol/24 h. Adherence was positively related to attendance at face-to-face contacts. Net decreases in SBP at 6, 18, and 36 months of 2.9 (P<0.001), 2.0 (P<0.001), and 1.3 (P=0.02) mmHg in sodium reduction vs usual care were associated with an overall 18% lower incidence of hypertension (P=0.048); were relatively unchanged by adjustment for ethnicity, gender, age, and baseline blood pressure, BMI, and sodium excretion; and were observed in both black and white men and women. From these beneficial but modest results with highly motivated and extensively counselled individuals, sodium reduction sufficient to favourably influence the population blood pressure distribution will be difficult to achieve without food supply changes.

Physician approach to the recognition and initial management of hypertension. Results of a statewide survey of Maryland physicians.

A representative sample of Maryland physicians in three practice settings (family/general, internal medicine, and specialty practice) participated in a survey designed to identify their attitudes toward patients with high blood pressure. Respondents recommended initial laboratory investigations more frequently and treatment at lower levels of blood pressure than was the case in a national physician survey performed in 1977. Family/general practitioners were the most cautious in respect to recommending antihypertensive drug therapy. They expressed greater enthusiasm, however, for nonpharmacologic treatment of hypertension and other cardiovascular risk factors. Physicians in each of the three practice settings expressed strong support for the use of diuretics as initial drug therapy in patients with mild hypertension. Impediments to long-term care were overwhelmingly believed to be patient- rather than physician-related.

Race and end-stage renal disease. Socioeconomic status and access to health care as mediating factors.

OBJECTIVE: To examine whether lower socioeconomic status and limited access to health care explain the racial inequities in the incidence of end-stage renal disease (ESRD), and whether these factors are independently associated with ESRD. METHODS: This case-control study compared 716 patients with ESRD with 361 population controls of the same age, 20 to 64 years old, from Maryland, Virginia, West Virginia, and Washington, DC. Race, indicators of socioeconomic status (household annual income, years of education), and indicators of access to health care (health insurance status, number of missing teeth, usual source of care, use of preventive services) were assessed via a telephone interview. RESULTS: Independent risk factors for ESRD included non-white race (odds ratio for blacks, 5.5; 95% confidence interval, 3.8 to 8.0; odds ratio for other nonwhites, 3.5; 95% confidence interval, 1.2 to 10.0), categories of income (odds ratio gradient, 1.0 to 4.5; 95% confidence interval, 2.6 to 7.8), receipt of Medicaid benefits (odds ratio, 3.5; 95% confidence interval, 1.5 to 8.4), and number of missing teeth (odds ratio gradient, 1.0 to 2.2; 95% confidence interval, 1.2 to 4.1). Adjustment for socioeconomic variables reduced the odds ratio for blacks only partially, from 8.1 to 5.5. The proportions of ESRD incidence that could be attributed to each risk factor were 46% for minority race, 53% for income categories, and 33% for missing teeth. CONCLUSIONS: Low socioeconomic status and limited access to health care were strong risk factors for kidney failure, but they explained only part of the excess of ESRD in blacks. Racial and social factors account for a large part of ESRD incidence. The mechanisms of these associations should be targeted by further research.

Community cholesterol screening. Impact of labeling on participant behavior.

To investigate the effect of screening for an elevated cholesterol level and compliance with follow-up recommendations, we surveyed 375 participants in a free screening program at a shopping mall walk-in clinic. One hundred thirty-nine participants (37%) had desirable (less than 5.17 mmol/L [less than 200 mg/dL]), 135 (36%) had borderline (5.17 to 6.18 mmol/L [200 to 239 mg/dL]), and 101 (27%) had high (greater than 6.18 mmol/L [greater than 239 mg/dL]) cholesterol levels. Persons in the borderline and high categories were instructed to see their physicians within 2 months for confirmation of their levels. Of the 338 (90%) who responded to a follow-up questionnaire at 3 months, 8 (7%) in the desirable, 23 (22%) in the borderline, and 44 (50%) in the high group had been to see physicians concerning their cholesterol levels since the screening. In multiple logistic regression analyses only cholesterol category at time of screening, current use of antihypertensive drugs, history of coronary heart disease, and history of a high cholesterol level were associated with physician follow-up. Our results suggest that labeling persons as being at high rather than borderline risk results in greater physician follow-up.

Effect of potassium supplementation on blood pressure in African Americans on a low-potassium diet. A randomized, double-blind, placebo-controlled trial.

OBJECTIVE: To determine the effect of potassium supplementation on blood pressure in African Americans consuming a low-potassium diet. DESIGN: Randomized, double-blind, placebo-controlled trial with two parallel arms. SETTING: Community-based research site. PARTICIPANTS: Eighty-seven healthy African Americans aged 27 to 65 years with a systolic blood pressure between 100 and 159 mm Hg and a diastolic blood pressure between 70 and 94 mm Hg. INTERVENTION: During the 21-day intervention period, all participants were provided with a low-potassium diet (32 to 35 mmol/d). In addition to this diet, they were randomly assigned to receive either potassium supplements (80 mmol/d) or placebo. MAIN OUTCOME MEASURE: Change in blood pressure in the potassium vs the placebo group, based on a total of nine blood pressure readings at three visits. Blood pressures were taken before and during the intervention by means of random-zero sphygmomanometry. RESULTS: At baseline, the placebo and potassium groups were similar for mean blood pressure (127/78 vs 125/77 mm Hg), 24-hour urinary potassium excretion (50 vs 44 mmol), and all other variables measured (all P > .05). During the intervention, the net difference in 24-hour urinary potassium excretion between groups was 70 mmol. Compared with the placebo group, the potassium supplementation group experienced a net decline in systolic blood pressure of 6.9 mm Hg (95% confidence interval, -9.3 to -4.4 mm Hg; P < .001) and a decline in diastolic blood pressure of 2.5 mm Hg (95% confidence interval, -4.3 to -0.8 mm Hg; P = .004). Simultaneous adjustment for differences in baseline characteristics only strengthened these estimates. CONCLUSIONS: Potassium supplementation reduces blood pressure substantially in African Americans consuming a diet low in potassium. Increased potassium intake may play an important role in reducing blood pressure in this population at high risk for hypertension.

Undetected eye disease in a primary care clinic population.

BACKGROUND: Population-based data have indicated that a significant proportion of persons with undiagnosed ocular disease in the community are regular users of general medical services. This, combined with the high prevalence of chronic medical disorders known to be risk factors for ocular disease in such clinics, makes them an attractive site for screening. METHODS: The prevalence of ocular disease was estimated in a sample of 405 general medicine patients attending an adult primary care clinic in an urban teaching hospital. RESULTS: Overall, 205 (50.6%) of 405 patients were found to have clinically important ocular pathology. One third of those affected (n = 68) were unaware of their eye disease, and 26% (n = 18) of these 68 patients required immediate medical or surgical intervention. Patients 65 years or older (odds ratio [OR], 1.76), in fair or poor general health (OR, 1.78), with diabetes mellitus (OR, 2.07), or with self-reported fair or poor vision (OR, 3.03), were at increased risk for the presence of ocular disease. Among patients with eye disease, those who had no insurance coverage for eye care (OR, 3.45), those who had not had an eye examination during the previous 2 years (OR, 4.03), and those whose last eye examination was performed by an optometrist (OR, 7.25, reference ophthalmologist) were more likely to not be aware of their eye disease. CONCLUSIONS: Our results underscore the importance of screening for ocular disease in primary health care settings, especially for patients who are older than 65 years, are in poor health, report poor vision, have had infrequent eye examinations, or have inadequate insurance coverage for eye care.

Does supplementation of diet with 'fish oil' reduce blood pressure? A meta-analysis of controlled clinical trials.

BACKGROUND: Several lines of evidence suggest that supplementation of diet with omega-3 polyunsaturated fatty acids (omega-3 PUFA), commonly referred to as fish oils, may reduce blood pressure (BP). However, most clinical trials of omega-3 PUFA supplementation have been of insufficient size to detect relevant BP changes. METHODS: We conducted a meta-analysis of 17 controlled clinical trials of omega-3 PUFA supplementation. To estimate an overall effect of omega-3 PUFA supplementation on BP, we calculated the net BP change in each trial (BP delta in omega-3 PUFA group minus BP delta in control group), which was then weighted according to the inverse of the variance. RESULTS: In the 11 trials that enrolled normotensive individuals (n = 728), omega-3 PUFA supplementation led to significant reductions of systolic BP (SBP) and diastolic BP (DBP) in two and one trials, respectively. In the six studies that enrolled untreated hypertensives (n = 291), significant reductions of SBP and DBP were present in two and four trials, respectively. Weighted, pooled estimates of SBP and DBP change (mm Hg) with 95% confidence intervals were -1.0 (-2.0 to 0.0) and -0.5 (-1.2 to +0.2) in the trials of normotensives, and -5.5 (-8.1 to -2.9) and -3.5 (-5.0 to -2.1) in the trials of untreated hypertensives. In 13 of 17 studies, trial duration was less than 3 months. Doses of omega-3 PUFA tended to be high (average dose > 3 g/d in 11 trials). The magnitude of BP reduction was greatest at high BP but was not significantly associated with dose of omega-3 PUFA. Side effects, most commonly eructation and a fishy taste, occurred more frequently in omega-3 PUFA participants than in control participants (28% vs 13%, P < .001). CONCLUSIONS: Our analyses indicate that diet supplementation with a relatively high dose of omega-3 PUFA, generally more than 3 g/d, can lead to clinically relevant BP reductions in individuals with untreated hypertension. However, use of omega-3 PUFA as antihypertensive therapy will require demonstration of long-term efficacy and patient acceptability of lower doses.

Does racial variation in risk factors explain black-white differences in the incidence of hypertensive end-stage renal disease?

Prospectively collected data on the incidence of treated hypertensive end-stage renal disease (HT-ESRD) were analyzed to investigate whether the higher rate of HT-ESRD in blacks compared with whites is due to differences in putative ESRD risk factors. The overall age-adjusted relative risks of HT-ESRD for black compared with white residents in the Maryland Regional ESRD Registry (Network 31) Catchment Area were 7.4 (95% confidence interval, 5.9 to 9.4) and 9.9 (95% confidence interval, 7.4 to 13.1) for men and women, respectively. In a population level analysis, race-specific HT-ESRD incidence rates in the black and white populations of 13 regions in Network 31 were related to the prevalence of putative ESRD risk factors in those populations. The latter were estimated from the 1981-1982 Maryland Statewide Household Hypertension Survey. Black populations had a 5.6-fold (95% confidence interval, 3.9 to 8.1) higher unadjusted incidence of HT-ESRD than white populations. The HT-ESRD incidence in a population was also directly related to that population's prevalence of hypertension, severe hypertension, and diabetes mellitus and inversely related to measures of socioeconomic status and mean age at diagnosis of hypertension. When adjusted simultaneously for age, prevalence of hypertension, severe hypertension, diabetes, and level of education, the risk of HT-ESRD was still 4.5 (95% confidence interval, 3.2 to 6.2) times higher for black compared with white populations. Our findings failed to support the hypothesis that race-related differences in the prevalence, severity, or age at onset of hypertension, in the prevalence of diabetes or in socioeconomic status, explain the well-recognized black-white differences in the HT-ESRD incidence.

Influence of renin levels on the treatment of essential hypertension with thiazide diuretics.

Initial plasma renin activity (PRA) was measured in 213 patients with untreated hypertension before beginning thiazide (chlorothiazide and hydrochlorothiazide) therapy alone to test whether patients with low-renin hypertension exhibited a greater response to diuretic therapy. Diastolic blood pressure response to treatment in the low, mid-range, and high PRA groups did not differ significantly (delta diastolic blood pressure, -13.6 +/- 1.6, -11.6 +/- 1.5, and -10.8 +/- 2.6 mm Hg, respectively). Moreover, eight subjects with the highest PRA values exhibited the same magnitude of decrease in diastolic blood pressure as did the low PRA group (15.0 +/- 4.2 vs 13.6 +/- 1.6, respectively). This study thus provides no evidence for increased sensitivity to diuretic therapy among patients with low-renin essential hypertension.

New guidelines for potassium replacement in clinical practice: a contemporary review by the National Council on Potassium in Clinical Practice.

This article is the result of a meeting of the National Council on Potassium in Clinical Practice. The Council, a multidisciplinary group comprising specialists in cardiology, hypertension, epidemiology, pharmacy, and compliance, was formed to examine the critical role of potassium in clinical practice. The goal of the Council was to assess the role of potassium in terms of current medical practice and future clinical applications. The primary outcome of the meeting was the development of guidelines for potassium replacement therapy. These guidelines represent a consensus of the Council members and are intended to provide a general approach to the prevention and treatment of hypokalemia.

Plasma insulin levels and incidence of hypertension in African Americans and whites.

BACKGROUND: Hyperinsulinemia may play an important role in the pathogenesis of hypertension in whites but the role of hyperinsulinemia in hypertension in African Americans is controversial. SUBJECTS AND METHODS: We studied the relationship between insulin levels and subsequent incidence of hypertension in 140 African Americans and 237 whites who were initially screened for possible participation in the Trials of Hypertension Prevention, phase 1. Plasma insulin and serum glucose were measured at baseline and at a follow-up examination 7 years later. Blood pressure was measured by trained observers using a random-zero sphygmomanometer. Incident hypertension was defined as an average systolic pressure of 160 mm Hg or higher and/or diastolic pressure of 95 mm Hg or higher at a single visit and/or use of antihypertensive medication during follow-up. RESULTS: Over the 7 years of follow-up, the incidence of hypertension was 25.7% in the African Americans and 25.3% in the whites. Baseline plasma insulin and insulin-to-glucose ratio were associated with an increased risk of hypertension in both the African Americans and the whites. After adjustment for age, sex, race, body mass, heart rate, and alcohol consumption at baseline as well as intervention assignment in the Trials of Hypertension Prevention, phase 1, a 1-SD (21 pmol/mmol) difference in baseline insulin-to-glucose ratio was associated with a 2.77 (95% confidence interval, 1.48-5.19) odds ratio of hypertension in the African Americans and a 1.69 (95% confidence interval, 1.08-2.64) odds ratio in the whites. CONCLUSION: These results suggest that higher plasma insulin levels are associated with an increased risk of hypertension in both African Americans and whites.

Risk factors for congestive heart failure in US men and women: NHANES I epidemiologic follow-up study.

BACKGROUND: The incidence of congestive heart failure (CHF) has been increasing steadily in the United States during the past 2 decades. We studied risk factors for CHF and their corresponding attributable risk in the First National Health and Nutrition Examination Survey Epidemiologic Follow-up Study. PARTICIPANTS AND METHODS: A total of 13 643 men and women without a history of CHF at baseline examination were included in this prospective cohort study. Risk factors were measured using standard methods between 1971 and 1975. Incidence of CHF was assessed using medical records and death certificates obtained between 1982 and 1984 and in 1986, 1987, and 1992. RESULTS: During average follow-up of 19 years, 1382 CHF cases were documented. Incidence of CHF was positively and significantly associated with male sex (relative risk [RR], 1.24; 95% confidence interval [CI], 1.10-1.39; P<.001; population attributable risk [PAR], 8.9%), less than a high school education (RR, 1.22; 95% CI, 1.04-1.42; P =.01; PAR, 8.9%), low physical activity (RR, 1.23; 95% CI, 1.09-1.38; P<.001; PAR, 9.2%), cigarette smoking (RR, 1.59; 95% CI, 1.39-1.83; P<.001; PAR, 17.1%), overweight (RR, 1.30; 95% CI, 1.12-1.52; P =.001; PAR, 8.0%), hypertension (RR, 1.40; 95% CI, 1.24-1.59; P<.001; PAR, 10.1%), diabetes (RR, 1.85; 95% CI, 1.51-2.28; P<.001; PAR, 3.1%), valvular heart disease (RR, 1.46; 95% CI, 1.17-1.82; P =.001; PAR, 2.2%), and coronary heart disease (RR, 8.11; 95% CI, 6.95-9.46; P<.001; PAR, 61.6%). CONCLUSIONS: Male sex, less education, physical inactivity, cigarette smoking, overweight, diabetes, hypertension, valvular heart disease, and coronary heart disease are all independent risk factors for CHF. More than 60% of the CHF that occurs in the US general population might be attributable to coronary heart disease.

Trends in pharmacologic management of hypertension in the United States.

BACKGROUND: Two new classes of antihypertensive agents were introduced in the 1980s, but their effectiveness in preventing heart disease and stroke has not been demonstrated. Lack of evidence of their efficacy might reasonably be expected to discourage their widespread use in management of hypertension. METHODS: Use of various classes of antihypertensive agents was estimated from published drug use information in an effort to estimate trends in antihypertensive drug use and evaluate the impact of these trends on costs of antihypertensive therapy in the United States. RESULTS: Proportionate use of the five major antihypertensive drug classes shifted markedly between 1982 and 1993. Diuretics accounted for 56% of all hypertensive drug mentions in 1982 but only 27% in 1993, a relative decline of 52%. Use of beta-blockers and central agents also declined during this period. Proportionate use of calcium antagonists showed the greatest gains, increasing from 0.3% to 27%, while the use of angiotensin-converting enzyme inhibitors increased from 0.8% to 24%. Given the higher costs of the newer agents, and assuming an estimated total cost of antihypertensive medications in 1992 of $7 billion, approximately $3.1 billion would have been saved had 1982 prescribing practices remained in effect in 1992. CONCLUSIONS: Use of calcium antagonists and angiotensin-converting enzyme inhibitors in hypertension has increased dramatically in the past 10 years. Without convincing evidence of the advantages of these agents, it is difficult to explain the continued decline in the use of less expensive agents, such as diuretics and beta-blockers, which are the only antihypertensive agents proved to reduce stroke and coronary disease in hypertensive patients.

Legume consumption and risk of coronary heart disease in US men and women: NHANES I Epidemiologic Follow-up Study.

BACKGROUND: Soybean protein and dietary fiber supplementation reduce serum cholesterol in randomized controlled trials. Consumption of legumes, which are high in bean protein and water-soluble fiber, may be associated with a reduced risk of coronary heart disease (CHD). METHODS: A total of 9632 men and women who participated in the First National Health and Nutrition Examination Survey Epidemiologic Follow-up Study (NHEFS) and were free of cardiovascular disease (CVD) at their baseline examination were included in this prospective cohort study. Frequency of legume intake was estimated using a 3-month food frequency questionnaire, and incidence of CHD and CVD was obtained from medical records and death certificates. RESULTS: Over an average of 19 years of follow-up, 1802 incident cases of CHD and 3680 incident cases of CVD were documented. Legume consumption was significantly and inversely associated with risk of CHD (P =.002 for trend) and CVD (P =.02 for trend) after adjustment for established CVD risk factors. Legume consumption 4 times or more per week compared with less than once a week was associated with a 22% lower risk of CHD (relative risk, 0.78; 95% confidence interval, 0.68-0.90) and an 11% lower risk of CVD (relative risk, 0.89; 95% confidence interval, 0.80-0.98). CONCLUSIONS: Our study indicates a significant inverse relationship between legume intake and risk of CHD and suggests that increasing legume intake may be an important part of a dietary approach to the primary prevention of CHD in the general population.

Dietary potassium intake and risk of stroke in US men and women: National Health and Nutrition Examination Survey I epidemiologic follow-up study.

BACKGROUND AND PURPOSE: The few prospective studies that have explored the association between dietary intake of potassium and risk of stroke have reported inconsistent findings. This study examines the relationship between dietary potassium intake and the risk of stroke in a representative sample of the US general population. METHODS: Study participants included 9805 US men and women who participated in the first National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Follow-Up Study. Dietary potassium and total energy intake were estimated at baseline by using a 24-hour dietary recall. Incidence data for stroke and coronary heart disease were obtained from medical records and death certificates. RESULTS: Over an average of 19 years of follow up, 927 stroke events and 1847 coronary heart disease events were documented. Overall, stroke hazard was significantly different among quartiles of potassium intake (likelihood ratio P=0.03); however, a test of linear trend across quartiles did not reach a customary level of statistical significance (P=0.14). Participants consuming a low potassium diet at baseline (<34.6 mmol potassium per day) experienced a 28% higher hazard of stroke (hazard ratio 1.28, 95% CI 1.11 to 1.47; P<0.001) than other participants, after adjustment for established cardiovascular disease risk factors. CONCLUSIONS: These findings suggest that low dietary potassium intake is associated with an increased risk of stroke. However, the possibility that the association is due to residual confounding cannot be entirely ruled out in this observational study.

Hypertension as a risk factor for renal disease. Review of clinical and epidemiological evidence.

Renal failure is a well-recognized complication of accelerated and malignant hypertension that can be prevented by appropriate antihypertensive therapy. The risk of renal disease in patients with milder forms of hypertension is less certain. Death certificate, insurance industry, and community-based observational studies provide little information with respect to the risk of kidney damage in the hypertensive patient. Randomized controlled trials of antihypertensive drug therapy provide equivocal results. The strongest evidence in support of the hypothesis that mild hypertension increases the risk of subsequent renal disease comes from analyses of the Hypertension Detection and Follow-up Program and the Medicare End-Stage Renal Disease (ESRD) Program. The risk of blood pressure-related ESRD appears to be especially high in blacks, independent of age, sex, and prevalence of hypertension. Although these results need to be confirmed, the data raise the possibility that the effects of high blood pressure on the kidney are different in blacks than in whites. Based on current trends, it is projected that the number of beneficiaries in the Medicare ESRD Program will continue to increase during the next 30-40 years and that the diagnosis of hypertensive ESRD will become increasingly common. Additional studies to characterize the relation between mild hypertension and subsequent risk of renal disease and to confirm the corresponding benefits of antihypertensive therapy are urgently needed.

Effect of age on the efficacy of blood pressure treatment strategies.

To study whether the proportion of excess cardiovascular events attributable to various levels of systolic blood pressure varies with age, we calculated the population-attributable risk of all-cause mortality, fatal and nonfatal cardiovascular events (stroke, coronary heart disease, angina, congestive heart failure, and peripheral vascular disease), and stroke incidence due to systolic blood pressure in men and women 45 years of age or older in the United States during 1980. Our estimates are based on US census counts, blood pressure prevalence distributions from the second National Health and Nutrition Examination Survey, and the annual risk of cardiovascular complications during 18 years of follow-up in the Framingham cohort. We then determined the impact of age on the relative efficacy of mass treatment and case-finding strategies in preventing systolic blood pressure-related events. At 45-54 years of age, only 30-40% of systolic blood pressure-related excess events occur in hypertensive individuals (systolic blood pressure greater than or equal to 160 mm Hg). With increasing age, however, the percentage of systolic blood pressure-related events that occur in hypertensive individuals rose substantially; in the older age group (greater than or equal to 75 years), 65-70% of fatal and nonfatal cardiovascular disease events occur in hypertensive persons. The pattern is similar for men and women. The potential impact of a mass treatment strategy designed to shift the distribution of blood pressure downward by a small amount is greater in younger than in older groups, whereas an opposite trend is seen for a high-risk, hypertensive case-finding and treatment approach.(ABSTRACT TRUNCATED AT 250 WORDS)