Anthropometry is an effective and frequently performed child health and nutrition screening procedure. The value of physical growth data depends on their accuracy and reliability, how they are recorded and interpreted, and what follow-up efforts are made after identification of growth abnormality. The new National Center for Health Statistics percentiles can be used to improve identification of potential health and nutritional problems and to facilitate the epidemological comparison of one group of children with others.

Abstract. Most visualization tools fail to provide support for missing data. In this paper, we identify sources of missing data and describe three levels of impact missing data can have on the visualization: perceivable, invisible or propagating. We then report on a user study with 30 participants that compared three design variants. A between-subject graph interpretation study provides strong evidence for the need of indicating the presence of missing information, and some direction for addressing the problem.

It has recently been reported that a low intake of calcium may be a risk factor for hypertension. In view of the contradictory results, even when the same survey data base has been used by different researchers, an in-depth analysis was undertaken of the data provided by the two cycles of the National Health and Nutrition Examination Survey (NHANES). Both surveys, conducted in consecutive 4-year intervals during the 1970s, were designed to examine representative samples of the U.S. civilian noninstitutionalized population. The overall descriptive findings in relation to mean blood pressure and calcium intake were virtually identical in the two surveys. Based on "quantile" analysis, neither mean levels of blood pressure nor the prevalence of hypertension was related to calcium intake. Only among black men in NHANES I was a relationship between calcium intake and blood pressure noted. This finding was not apparent among black men in NHANES II or among any of the other sex-race groups in either survey. We conclude that the data of NHANES I and II do not show an association between low calcium intake and blood pressure.

SUMMARY Intensive efforts by practicing physicians and public health workers to identify and treat persons with hypertension have been underway for many years. In this report, changes in blood pressure levels in the United States are assessed based on nationally representative health (and nutrition) examination surveys conducted by the National Center for Health Statistics in 1960Statistics in to 1962Statistics in , 1971Statistics in to 1974Statistics in , and 1976Statistics in to 1980. Analysis of age-adjusted data for adults aged 18 to 74 years (including those on antihypertensive medication) indicates that between the first and third surveys for whites and blacks, respectively, mean systolic blood pressure declined 5 and 10 mm Hg; the proportion of persons with systolic blood pressure of 140 mm Hg or higher fell 18 and 31 %; the proportion with undiagnosed hypertension decreased 17 and 59%; and the proportion taking antihypertensive medications rose 71 and 3 1 % . These differences between the first and third surveys were all statistically significant (p<0.05 or better). Changes in diastolic blood pressure levels were generally not significant among race-sex groups. The proportion of persons with definite hypertension (i.e., systolic blood pressure > 160 mm Hg, and/or diastolic blood pressure a 95 mm Hg, and/or taking antihypertensive medication) declined among blacks but rose slightly among whites. Study results are consistent with the recent decline in cardiovascular disease mortality. (Hypertension 10: 226-233, 1987) KEY WORDS • blood pressure • hypertension • health surveys • United States A FTER many years of substantial efforts to edu-/ \ cate the public and health care providers A. \ . about hypertension and to identify and treat persons with the disease, it is useful to assess the overall impact of such programs on blood pressure levels in the U.S. adult population. This report presents changes in blood pressure levels based on data from three large representative national health surveys conducted in the period

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