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High intakes of dietary sodium are associated with elevated blood pressure levels and an increased risk of cardiovascular disease. National and international guidelines recommend reduced sodium intake in the general population, which necessitates population-wide surveillance. We assessed the utility of casual (spot) urine specimens in estimating 24-hour urinary sodium excretion as a marker of sodium intake in the International Cooperative Study on Salt, Other Factors, and Blood Pressure. There were 5,693 participants recruited in 1984–1987 at the ages of 20–59 years from 29 North American and European samples. Participants were randomly assigned to test or validation data sets. Equations derived from casual urinary sodium concentration and other variables in the test data were applied to the validation data set. Correlations between observed and estimated 24-hour sodium excretion were 0.50 for individual men and 0.51 for individual women; the values were 0.79 and 0.71, respectively, for population samples. Bias in mean values (observed minus estimated) was small; for men and women, the values were −1.6 mmol per 24 hours and 2.3 mmol per 24 hours, respectively, at the individual level and −1.8 mmol per 24 hours and 2.2 mmol per 24 hours, respectively, at the population level. Proportions of individuals with urinary 24-hour sodium excretion above the recommended levels were slightly overestimated by the models. Casual urine specimens may be a useful, low-burden, low-cost alternative to 24-hour urine collections for estimation of population sodium intakes; ongoing calibration with study-specific 24-hour urinary collections is recommended to increase validity.

Background Association between casual and 24-h urinary sodium-to-potassium (Na/K) ratio is well recognized, although it has not been validated in diverse demographic groups. Our aim was to assess utility across and within populations of casual urine to estimate 24-h urinary Na/K ratio using data from the INTERSALT Study. Methods The INTERSALT Study collected cross-sectional standardized data on casual urinary sodium and potassium and also on timed 24-h urinary sodium and potassium for 10 065 individuals from 52 population samples in 32 countries (1985–87). Pearson correlation coefficients and agreement were computed for Na/K ratio of casual urine against 24-h urinary Na/K ratio both at population and individual levels. Results Pearson correlation coefficients relating means of 24-h urine and casual urine Na/K ratio were r = 0.96 and r = 0.69 in analyses across populations and individuals, respectively. Correlations of casual urine Na/creatinine and K/creatinine ratios with 24-h urinary Na and K excretion, respectively, were lower than correlation of casual and 24-h urinary Na/K ratio in analyses across populations and individuals. The bias estimate with the Bland–Altman method, defined as the difference between Na/K ratio of 24-h urine and casual urine, was approximately 0.4 across both populations and individuals. Spread around, the mean bias was higher for individuals than populations. Conclusion With appropriate bias correction, casual urine Na/K ratio may be a useful, low-burden alternative method to 24-h urine for estimation of population urinary Na/K ratio. It may also be applicable for assessment of the urinary Na/K ratio of individuals, with use of repeated measurements to reduce measurement error and increase precision.

Data indicate an inverse association between dietary calcium and magnesium intakes and blood pressure (BP); however, much less is known about associations between urinary calcium and magnesium excretion and BP in general populations. The authors assessed the relation of BP to 24-hour excretion of calcium and magnesium in 2 cross-sectional studies. The International Study of Macro- and Micro-Nutrients and Blood Pressure (INTERMAP) comprised 4,679 persons aged 40–59 years from 17 population samples in China, Japan, the United Kingdom, and the United States, and the International Cooperative Study on Salt, Other Factors, and Blood Pressure (INTERSALT) comprised 10,067 persons aged 20–59 years from 52 samples around the world. Timed 24-hour urine collections, BP measurements, and nutrient data from four 24-hour dietary recalls (INTERMAP) were collected. In multiple linear regression analyses, urinary calcium excretion was directly associated with BP. After adjustment for multiple confounders (including weight, height, alcohol intake, calcium intake, urinary sodium level, and urinary potassium intake), systolic BP was 1.9 mm Hg higher per each 4.1 mmol per 24 hours (2 standard deviations) of higher urinary calcium excretion (associations were smaller for diastolic BP) in INTERMAP. Qualitatively similar associations were observed in INTERSALT analyses. Associations between magnesium excretion and BP were small and nonsignificant for most of the models examined. The present data suggest that altered calcium homoeostasis, as exhibited by increased calcium excretion, is associated with higher BP levels.

Twenty-four-hour urinary albumin excretion (UAE) is considered the gold standard for determining albumin level in epidemiologic studies, but this measure is inconvenient and often unavailable. Simpler alternatives include the albumin:creatinine ratio (ACR) and urinary albumin concentration (UAC) obtained from a single sample. The authors assessed the strengths and weaknesses of ACR and UAC as alternatives to UAE using albumin measurements from two 24-hour urine samples collected in 1996–1999 from 4,678 participants aged 40–59 years in the International Study of Macronutrients and Blood Pressure (17 population samples from four countries). The authors compared ACR and UAC with regard to correlations with UAE, daily within-person variability, and associations with known predictors of UAE. Rank-order correlations of ACR with UAE were 0.949 and 0.942 for men and women, respectively, versus 0.881 and 0.816 for UAC. Mean within-person coefficients of variation were 34.0–40.0% for the three measures, with the smallest values being observed for UAC. Average correlations with blood pressure were similar for UAE, ACR, and UAC, but the correlation with body mass index was lower for ACR (0.118 for ACR and 0.188 for UAC vs. 0.211 for UAE) because of high correlation between body mass index and creatinine level. Thus, UAC and ACR are acceptable alternatives to the more complex UAE, and the simpler UAC may be preferable to ACR in some respects.

Research on response rates to surveys mailed to study participants decades after baseline examination, with minimal interim contact, is limited. This paper documents response rates to a 26-year follow-up survey of surviving participants from a large cohort in Illinois and compares baseline characteristics of nonrespondents and respondents. Mortality follow-up of the Chicago Heart Association Detection Project in Industry 1967-1973 cohort involved minimal or no participant contact since baseline. In 1996, a 26-year follow-up questionnaire was mailed to all surviving participants aged 65 years or older. Current addresses were obtained from the Health Care Financing Administration for 96.5 percent of 12,409 participants in our analyses. Total response rates were 59.8 percent and, for participants for whom Health Care Financing Administration addresses were available, 60.8 percent. A higher response rate was obtained for younger recipients, men, Whites, more-educated persons, nonsmokers, and those with a better cardiovascular risk profile at baseline. A graded negative relation was found between number of cardiovascular risk factors at baseline and response rates obtained in 1996. Use of Health Care Financing Administration records as an additional follow-up method and factors that influence response rates are discussed. In conclusion, long-term follow-up of older surviving participants is feasible if current addresses can be obtained from standardized sources.

In a prospective cohort study, associations of resting heart rate with risk of coronary, cardiovascular disease, cancer, and all-cause mortality in age-specific cohorts of black and white men and women were examined over 22 years of follow-up. Participants were employees from 84 companies and organizations in the Chicago, Illinois, area who volunteered for a screening examination. Participants included 9,706 men aged 18-39 years, 7,760 men aged 40-59 years, 1,321 men aged 60-74 years, 6,928 women aged 18-39 years, 6,915 women aged 40-59 years, and 1,151 women aged 60-74 years at the baseline examination in 1967-1973. Vital status was ascertained through 1992. For fatal coronary disease, multivariate-adjusted relative risks associated with a 12 beats per minute higher heart rate (one standard deviation) were as follows: for men aged 18-39 years, relative risk (RR) = 1.27 (95% confidence interval (CI) 1.08-1.48); for men aged 40-59 years, RR = 1.13 (95% CI 1.05-1.21); for men aged 60-74 years, RR = 1.00 (95% CI 0.89-1.12); for women aged 40-59 years, RR = 1.21 (95% CI 1.07-1.36); and for women aged 60-74 years, RR = 1.16 (95% CI 0.99-1.37). Corresponding risks for all fatal cardiovascular diseases were similar to those for coronary death alone. Deaths from cancer were significantly associated with heart rate in men and women aged 40-59 years. All-cause mortality was associated with higher heart rate in men aged 18-39 years (RR = 1.11, 95% CI 1.01-1.20), men aged 40-59 years (RR = 1.16, 95% CI 1.11-1.21), and women aged 40-59 years (RR = 1.20, 95% CI 1.13-1.27). Heart rate was not associated with mortality in women aged 18-39 years. In summary, heart rate was a risk factor for mortality from coronary disease, all cardiovascular diseases, and all causes in younger men and in middle-aged men and women, and for cancer mortality in middle-aged men and women.

Background. High salt and nitrate intake are considered as risk factors for stomach cancer, but little is known about possible interactions. This ecological study examines the respective importance of both factors for stomach cancer mortality at the population level using data obtained under standardized conditions and with biochemical analyses performed in the same laboratories. Method. Randomly selected 24-hour urine samples from 39 populations, sampled from 24 countries (N = 5756 people for sodium, 3303 for nitrate) were obtained from the INTERSALT study. Median sodium and nitrate levels were age- and sex-standardized between ages 20-49 years and averaged per country. Ecological correlation-regression analyses were done in relation to national stomach cancer mortality rates. Results. The Pearson correlation of stomach cancer mortality with sodium for the 24 countries was : 0.70 in men and 0.74 in women (both P < 0.001), and with nitrate : 0.63 (P = 0.001) in men and 0.56 (P < 0.005) in women. In multiple regression of stomach cancer mortality, using sodium and nitrate as independent variables, the adjusted R 2 was 0.61 in men and 0.54 in women (both P < 0.001). Addition of the interaction term (sodium x nitrate) to the previous model increased the adjusted R 2 to 0.77 in men, and to 0.63 in women. The analysis of this model showed that the importance of nitrate as risk factor for stomach cancer mortality increased markedly with higher sodium levels. However, the relationship of stomach cancer mortality with sodium was always stronger than with nitrate. Conclusions. Salt intake, measured as 24-hour urine sodium excretion, is likely the rate-limiting factor of stomach cancer mortality at the population level.

Background. There is considerable interest in the possible role of nitrate in gastric carcinogenesis, but little information on nitrate intake around the world. This is the first study to give comprehensive standardized data on nitrate excretion as a marker of intake, using 48 worldwide population samples. Methods. Urinary nitrate excretion has been shown to be a valid measure of nitrate intake in people under 50. This report presents data on 24-hour urinary nitrate excretion from urine collections obtained in the INTERSALT study, based on random samples of men and women aged 20-49 from each of 48 population samples in 30 countries. Results. There was large variation in urinary nitrate excretion both within and between samples ; within-sample (individual) distributions tended to be skewed towards higher values. Median values of the samples ranged from 0.42 mmol/day (Labrador, Canada) to 3.52 (Beijing, People's Republic of China) in men and 0.44 mmol/day (Colombia) to 3.44 (Beijing) in women. Overall, median values were higher in men than women by 11% on average (higher in men in 37 of 48 population samples). Comparison by geographical region of median values for men and women combined showed relatively low values in the samples in North America and Northern Europe (range 0.46-0.88 mmollday), slightly higher values in Western Europe and Africa (0.68-1.11), and intermediate to high values in Southern Europe, Eastern and Central Europe and India (0.86-2.47). The highest median values were found in the Far Eastern samples (up to 3.48). Median values in the Central and South American samples ranged from 0.48 mmol/day (Colombia) to 1.37 (Xingu Indians of Brazil, and Argentina). Conclusions. For the first time, these data give standardized information on urinary nitrate excretion from different geographical regions of the world, and provide a basis for the further exploration of the role of nitrate in the aetiology of disease in human populations.

Associations of parents' education and smoking with young adults' smoking were examined in participants aged 18-30 years at baseline (1985-1986) in the Coronary Artery Risk Development in Young Adults study. Significant (p < 0.05) inverse age-adjusted associations of father's education with participant smoking status among black men, white men, and white women disappeared after adjustment for participant's education. Parental smoking status was directly related to participant smoking status for all race/sex groups. Participant education was strongly inversely related to participant smoking. Public health campaigns should consider influences of parental behaviors on children's behaviors and associations of limited education with adverse lifestyles.

This is the first of two reports dealing with the reliability of measurements of 24-hour urinary electrolyte excretion and blood pressure and estimates of electrolyte-blood pressure associations in INTERSALT, an international study of the relations of electrolyte excretion and other factors to blood pressure, involving more than 10,000 persons from 52 centers in 32 countries. This first report describes methods for estimating reliability, taking into account age and sex, and provides estimates for several urinary variables, blood pressure, and pulse rate. The second report (Am J Epidemiol 1994; 139:940-51) uses these estimates of reliability and multivariate procedures to correct multiple regression coefficients from regressions of blood pressure on 24-hour urinary sodium and potassium excretion, body mass index, and alcohol intake for "regression dilution bias." Age- and sex-adjusted estimates of reliability were computed from data on 805 INTERSALT participants with repeat measurements. These estimates ranged from 0.37 to 0.40 for 24-hour urinary sodium, from 0.47 to 0.52 for potassium, from 0.32 to 0.36 for the sodium:potassium ratio, from 0.64 to 0.69 for calcium, from 0.59 to 0.65 for creatinine, from 0.49 to 0.57 for urinary volume, from 0.49 to 0.51 for magnesium, from 0.58 to 0.62 for pulse, from 0.69 to 0.74 for systolic blood pressure, and from 0.63 to 0.67 for diastolic blood pressure. In addition, estimates of within- and between-person covariances among electrolytes indicated that about half of the observed covariance for sodium and potassium excretion in a single 24-hour urine collection was due to within-person covariation in excretion.

The authors examined associations of caffeine and caffeinated beverage intakes with blood pressure and with lipoproteins in 5,115 black and white men and women aged 18-30 years during 1985-1986. Caffeine and beverage intakes were not consistently associated with blood pressure in analyses controlling for race, sex, Keys score, sucrose intake, physical activity, oral contraceptive use, body mass index, alcohol use, age, and smoking. Associations of caffeine and beverage intakes with cholesterol, triglycerides, high-density lipoprotein cholesterol, and high-density lipoprotein2 cholesterol were also inconsistent. There is little or no association of caffeine with lipoproteins or with blood pressure in this cohort of healthy young adults.

Young adult blacks and whites aged 18-30 years of both low and high educational levels were recruited through random digit dialing to participate in the Chicago, Illinois, portion of a longitudinal study, Coronary Artery Risk Development in Young Adults (CARDIA). Overall, 31% of randomly selected persons eligible to participate had unlisted telephone numbers--about 50% of black men and women and 11% and 17% of white men and women, respectively. There was no difference in proportions of numbers unlisted by educational level, except for white men, who were more likely to have unlisted numbers at a low educational level than at a high educational level. There was no consistent pattern of differences in rates of participation across race, sex, or education subgroups for unlisted and listed numbers, and there were no significant differences for selected health measures, except smoking. The findings suggest that in Chicago, there is a potential bias in estimates of sociodemographic characteristics from the exclusion of unlisted numbers, but it is likely to be insignificant if recruitment is stratified according to race, sex, and education. Within strata, there was little bias with respect to the attributes measured. Ideally, to guard against possible bias, random digit dialing is recommended as the preferred way to select a representative population-based sample.

The relation of post-load plasma glucose to 12-year cancer mortality was studied in 11,521 white men and 8,591 white women aged 35-64 years at entry in the Chicago Heart Association Detection Project in Industry. There were 298 deaths in which cancer was the underlying cause in men and 186 such deaths in women. Plasma glucose levels at baseline measured one hour after a 50 g oral glucose load were positively related to cancer mortality in men but not in women. This increased mortality in men persisted after controlling for age, body mass index, smoking, serum cholesterol, systolic blood pressure, education, and anti-hypertensive treatment. A site-specific analysis of the male cancer deaths demonstrated higher mean plasma glucose levels for decedents for nearly all sites except oral cancers, liver cancer, and other respiratory cancers. For women, elevations existed for those who died of colon, lung, and hematologic/lymphatic tumors, but not for most other sites. The associations between baseline post-load plasma glucose levels and cancer mortality were similar for earlier and later cancer deaths, which indicates that incipient or occult neoplasm at baseline was not responsible for elevated glucose levels in men who subsequently died of cancer. Cancer mortality rates were also higher for those with a clinical diagnosis of diabetes than for those without, but the numbers of persons with diabetes were small as were the numbers of cancer deaths (19 in the men and 10 in the women).

In 1970, 250,000 Spanish-speaking persons resided in Chicago, 80,000 of whom were Puerto Rican. Because migration to Chicago is constantly occurring from areas where intestinal parasites are endemic, a survey was conducted in a predominantly Puerto Rican neighborhood to determine the prevalence of these parasites and to provide impetus for further case finding and treatment programs. The survey was part of an epidemiologic and cutreach workers going door-to-door obtained histories, hematocrits, and single stool specimens from 358 individuals. An overall intestinal parasite prevalence rate of 18.6% (67 persons) was found. Specific rates were Trichuris trichiura 13.9% (50 cases), hookworm 6.6% (24 cases), Giardia lamblia (3.9% (14 cases), and Strongyloides stercoralis 1.7% (6 cases). There were no cases of Ascaris lumbricoides or ENTAMOEBA HISTOLYTICA, Although several nonpathogenic protozoa were found. The most affected age groups were 15--24 years followed by 5--14. Two of the Giardia cases were individuals never out of the continental United States. An incidental finding was a high rate of low hematocrit readings not correlated with the parasite findings.

This paper explores time trends in racial differences in hypertension and in mortality from complications from hypertension in the United States. Mortality data were derived from death certificate data compiled by the National Center for Health Statistics and presented in the 1981 Report of the Working Group on Arteriosclerosis. Prevalence data were obtained from five populations--6,672 people screened in 1960-1962 by the National Health Examination Survey (NHES); 20,749 screened in 1971-1975 by the Health and Nutrition Examination Survey (HANES I); 158,539 screened in 1973-1974 by the Hypertension Detection and Followup Program (HDFP); 1 million persons screened in 1973-1975 by the Community Hypertension Evaluation Clinics (CHEC); and 20,325 screened in 1976-1980 by the second Health and Nutrition Examination Survey (HANES II). Mortality data indicate that the nonwhite/white ratios for mortality from complications of hypertension increased between 1940 and 1967 and decreased between 1968 and 1978. Prevalence data show a corresponding recent decrease in black minus white mean blood pressure. Some of the decrease appears to be due to a greater improvement in hypertension control for blacks than for whites. Time trends in the black/white ratio in prevalence of hypertension were examined with differential treatment effects controlled by inclusion as hypertensive those on drug therapy. The results indicate that in addition to differential changes in therapy, the ratio of black/white prevalence of hypertension may also be decreasing. Additional studies are needed to confirm this finding and to explore time changes in racial patterns of risk factors for hypertension.

The associations between heart rate and death from the cardiovascular diseases (CVD), coronary heart disease (CHD) and sudden death from CHD, along with death from all causes and non-cardiovascular causes, are examined for three groups of middle-aged white males: 1233 men aged 40-59 years followed for 15 years from the Chicago Peoples Gas Company study; 1899 men aged 40-55 years followed for 17 years from the Chicago Western Electric Company study; and 5784 men aged 45-64 years followed an average of five years from the Chicago Heart Association Detection Project in Industry. In univariate analyses, mortality from both cardiovascular and non-cardiovascular causes generally increases with increasing heart rate. In bivariate analyses, using the Cox regression model to control for age, heart rate is significantly related to mortality from all causes in each study, with the associations again due to both cardiovascular and non-cardiovascular causes. In multivariate Cox regression, controlling for age, blood pressure, serum cholesterol, cigarettes smoked per day and relative weight, heart rate is a significant risk factor for sudden CHD death and non-CVD death in two of the three studies, with the association with sudden death being U-shaped in one of the studies. Although heart rate may be an independent risk factor for sudden CHD death, the associations with other CVD death and non-sudden CHD death, in general, appear to be secondary to associations between heart rate and other cardiovascular risk factors.

The relations between coffee consumption and 19-year mortality from all causes, coronary heart disease, and non-coronary causes were assessed in 1,910 white males aged 40-56 years in 1957-1958 from the Chicago Western Electric Company Study. Mortality rates, adjusted for age, serum cholesterol, diastolic blood pressure, and smoking status, were compared for those consuming 0-1, 2-3, 4-5, and 6+ cups of coffee per day; coffee intake, measured at the first anniversary examination, included both caffeinated and decaffeinated intake. Mortality from all causes was greatest in the highest and lowest intake groups. The increased mortality in the 6+ cups per day group was due to coronary heart disease, while the increased mortality in the lowest intake group was due to noncoronary causes. The adjusted relative risk of coronary heart disease death for those drinking 6+ cups of coffee per day compared with those drinking less was 1.71 (95 per cent confidence limits 1.27, 2.30). This increased risk of coronary heart disease death was present in both smokers and nonsmokers, with adjusted relative risks of 1.62 and 2.21, respectively (95 per cent confidence limits 1.17, 2.24 and 1.06, 4.62). The increased mortality from non-coronary causes in the lowest intake group was due primarily to increased mortality from cancer and cardiovascular diseases other than coronary heart disease. The results of this study support the hypothesis that those who drink 6+ cups of coffee per day may be at an increased risk of death from coronary heart disease.

SUMMARY The purposes of this paper are to provide some additional results on the comparison of tests for normality and to indicate in the light of a somewhat startling result the need for caution in the use of these tests. The most notable efforts at comparing tests for normality are those of Shapiro, Wilk & Chen (1968), Lilliefors (1967) and of an unpublished Stanford University report of M. A. Stephens. The efforts of these authors have, however, been con- fined to the case where both It and o2 are assumed unknown. In this article, we consider two cases, the first, where both the mean, ,u, and the variance, o2, of the normal distribution are assumed unknown, and the second, where only -2 is assumed unknown. It is the comparison of the results between these two cases which leads to the cautionary note. It is hoped that our results will help serve as a guide in the use of such tests.

This epidemiologic study explored the sex differential in risk of death from coronary heart disease in persons with or without clinically diagnosed diabetes or asymptomatic hyperglycemia. Use was made of 9-year follow-up data from the Chicago Heart Association Detection Project in Industry for 11,220 white men and 8,030 white women aged 35-64 years at entry to the Project (November 1967-January 1973). Both clinically diagnosed diabetes and asymptomatic hyperglycemia were associated with an increased risk of death from coronary heart disease. The extent of this association was greater in women than in men in regard to relative risk. However, absolute excess risk for both diabetics and those with asymptomatic hyperglycemia was larger for men than for women. Clinical diabetes appeared to be an independent risk factor for coronary heart disease in both men and women based on multivariate Cox regression analyses. On the other hand, for men, no significant independent effect of asymptomatic hyperglycemia was apparent. Women with asymptomatic hyperglycemia had significantly higher coronary heart disease death rates than normoglycemic women, with adjustment for major coronary heart disease risk factors; in multivariate analyses, the relationship of asymptomatic hyperglycemia to risk of coronary heart disease was of borderline significance (p = 0.054). This study indicates the independent associations of diabetes and possibly asymptomatic hyperglycemia with coronary heart disease mortality, with greater relative significance in women than in men.

The relationship between heart rate and cancer mortality was examined in 3 Chicago epidemiologic studies: 1233 white men originally age 40-59 followed 18 years from the Chicago Peoples Gas Company study; 1899 white men originally age 40-55 followed 17 years from the Chicago Western Electric Company study; 5784 white men originally age 45-64 followed 5 years from the Chicago Heart Association Detection Project in Industry. There was a significant association between heart rate and cancer mortality in both univariate and multivariate analyses in men from the Gas Company study and in men from the Chicago Heart Association study, but there was no association between heart rate and cancer mortality in men from the Western Electric study. The relationship persisted in the Gas Company study but not in the Chicago Heart Association study after eliminating deaths within the first 2 years of follow-up. With cancer deaths broken down by the site, mortality from lung and colon cancer in the Gas Company study and mortality from lung cancer in the Chicago Heart Association study were significantly associated with baseline heart rate on univariate analysis and on bivariate analysis controlling for age. Only colon cancer in the Gas Company, however, remained associated with heart rate when other variables were controlled. Thus, in 2 of the 3 studies examined, heart rate appeared to be an independent risk factor for cancer mortality in men.

A statistic, Q, based on the ranks of the estimated probabilities of disease is proposed for assessing the effectiveness of regression models used with dichotomous dependent variables in epidemiologic studies of risk factors for chronic diseases. The pitfalls of R2 are discussed, and the proposed statistic is compared with R2 utilizing 8.6-year incidence data from the national cooperative Pooling Project and 15-year mortality data from the Chicago Peoples Gas Company Study. Based on the risk factors, systolic blood pressure, serum cholesterol, and smoking status for middle-aged males, the proposed statistic, Q, attains from 27-44% of its maximum value for the endpoint, the first major coronary event, and from 35-46% of the maximum for death from the cardiovascular diseases.