Ambulatory health care visits by children: principal diagnosis and place of visit.

OBJECTIVES: This report presents national estimates of ambulatory health care use by children under 15 years of age according to principal diagnosis, place of visit (physician office, hospital outpatient department, and hospital emergency department), and patient characteristics (age, sex, and race). METHODS: Data were from the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey. Data were from 1993-95. RESULTS: In 1993-95 children under 15 years of age made 165.3 million visits per year (289 visits per 100 children). Visit rates were highest among infants and varied inversely with age. Visit rates were 43 percent higher among white children than black children. Three-quarters of ambulatory visits occurred in physician offices, 8 percent in hospital outpatient departments, and 14 percent in hospital emergency departments. Visits by white children were more likely to occur in physician offices than visits by black children (81 percent and 54 percent). Conversely, visits by black children were more likely to occur in hospital outpatient departments (19 percent and 7 percent) and hospital emergency departments (28 percent and 12 percent) than visits by white children. The following principal diagnoses accounted for almost 40 percent of visits: well-child visit, 15 percent; middle ear infection, 12 percent; and injury, 10 percent. Rates for well-child visits were almost 80 percent higher among white infants than black infants. Continued monitoring of these differences in use of ambulatory care among children are needed, particularly in view of the possible impact of changes in the health care system on these differences.

Statistical issues in analyzing the NHANES I Epidemiologic Followup Study. Series 2: Data evaluation and methods research.

This report presents alternative strategies for analysis of data from the NHANES I Epidemiologic Followup Study (NHEFS) using Cox proportional hazards and person-time logistic regression models. Analytic issues related to the complex survey design of the NHANES I and the variable length of followup of NHEFS participants are discussed.

Health service areas for the United States.

The objectives of this report are to document methods used to identify health service areas for the United States and to describe and evaluate these areas. A health service area is defined as one or more counties that are relatively self-contained with respect to the provision of routine hospital care. Service areas that include more than one county are characterized by travel between the counties for routine hospital care.

Is weight loss a modifier of the cholesterol-heart disease relationship in older persons? Data from the NHANES I Epidemiologic Follow-up Study.

The relationship between cholesterol and 14-year incidence of coronary heart disease was compared for men and women of two age groups, 25 to 64 years and 65 to 74 years. While cholesterol levels of 6.2 mmol/L or higher were associated with a risk of coronary heart disease in the younger group, this was not true for either men or women aged 65 to 74. Further analyses for older persons showed that weight loss modified the cholesterol-heart disease relationship. Those with stable weight showed a positive relationship between cholesterol and coronary heart disease, similar to the younger age group (relative risk [RR] = 1.8 [95% confidence interval: 1.1, 2.9] for men; RR = 1.6 [.7, 3.4] for women). Among those with a weight loss of 10% or more, the relationship of cholesterol to heart disease was inverse (RR = .8 [.5, 1.2] for men; RR = .6 [.3, 1.0] for women). These data suggest that the relationship of cholesterol to coronary disease in healthier older persons may be similar to that in younger persons, and that health status should be considered in analyses of cholesterol risk in old age.

Erythrocyte sedimentation rate and coronary heart disease: the NHANES I Epidemiologic Follow-up Study.

Erythrocyte sedimentation rate (ESR) is a simple and relatively inexpensive laboratory test. Data were examined to determine whether elevated ESR was a predictor of CHD incidence and death in a large U.S. national sample of persons aged 45-74 at baseline. In the NHANES I Epidemiologic Follow-up Study cohort, white men aged 45-64 years with ESR in the upper quintile at baseline had increased incidence of CHD (RR = 1.73, 95% CL 1.12, 2.68) over a 15 year follow-up after controlling multiple risk factors compared to white men with ESR in the lowest quintile. Furthermore, men aged 45-64 with ESR in the upper quintile had more than twice the risk of CHD death (RR = 2.73, 95% CL 1.21, 6.15) of men with ESR in the lowest quintile after adjusting other risk factors. No significant associations were seen in white women. The mechanism of this association is unclear. Further studies are needed to replicate this finding and elucidate the mechanism for this association in longitudinal studies in which plasma fibrinogen, HDL cholesterol, as well as ESR are measured.

The low cholesterol-mortality association in a national cohort.

The relationship of low serum cholesterol and mortality was examined in data from the NHANES I Epidemiologic Followup Study (NHEFS) for 10,295 persons aged 35-74, 5833 women with 1281 deaths and 4462 men with 1748 deaths (mean (followup = 14.1 years). Serum cholesterol below 4.1 mmol/l was associated with increased risk of death in comparison with serum cholesterol of 4.1-5.1 mmol/l (relative risk (RR) for women = 1.7, 95% confidence interval (CI) = (1.2, 2.3); for men RR = 1.4, CI = (1.1, 1.7)). However, the low serum cholesterol-mortality relationship was modified by time, age, and among older persons, activity level. The low serum cholesterol-mortality association was strongest in the first 10 years of followup. Moreover, this relationship occurred primarily among older persons (RR for low serum cholesterol for women 35-59 = 1.0 (0.6, 1.8), for women 70-74, RR = 2.1 (1.2, 3.7); RR for low serum cholesterol for men 35-59 = 1.2 (0.8, 2.0), for men 70-74, RR = 1.9 (1.3, 2.7)). Among older persons, however, the low serum cholesterol-mortality association was confined only to those with low activity at baseline. Factors related to underlying health status, rather than a mortality-enhancing effect of low cholesterol, likely accounts for the excess risk of death among persons with low cholesterol. The observed low cholesterol-mortality association therefore should not discourage public health programs directed at lowering serum cholesterol.

Is the serum cholesterol-coronary heart disease relationship modified by activity level in older persons?

Although coronary heart disease remains a leading cause of death and disability in old age, the relationship of serum cholesterol level to risk of coronary heart disease in old age is controversial. Data for 2,388 white persons aged 65-74 who participated in the National Health and Nutrition Examination Survey (NHANES) I Epidemiologic Follow-up Study (NHEFS) were examined to determine the relationship of serum cholesterol level to coronary heart disease incidence and whether activity level would modify this relationship. While there was no overall relationship between serum cholesterol level and coronary heart disease risk in either men or women, the relationship between serum cholesterol level and coronary heart disease differed within activity groups. For persons who were more active, serum cholesterol level was associated with a graded increase in risk of coronary heart disease, from 1.3 (95% CI 0.7, 2.3) in those with serum cholesterol level of 4.7-5.1 to 1.7 in those with serum cholesterol level of 6.2 mmol/L or more (95% CI 1.0, 2.7), when compared with those with serum cholesterol level below 4.7. For the least active persons, all levels of cholesterol were associated with a significant inverse relative risk, including cholesterol of 6.2 mmol/L or more (Relative risk = 0.4 (95% CI 0.2, 0.7]. These data suggest that factors such as activity level may modify the serum cholesterol-coronary heart disease association in old age. The serum cholesterol-coronary heart disease association in more active older persons resembles that seen in younger populations, whereas the association in less active persons is that of serum cholesterol level and risk of cancer or death. The modification of the serum cholesterol-coronary heart disease association by activity level may have implications for appropriate clinical management as well as appropriate design of research studies of this association.

Service areas for ambulatory medical care.

This article evaluates three alternative definitions of physician service areas using data from the 1978 National Health Interview Survey. The three types of areas are county aggregations based on different data sources: the Bureau of Economic Analysis Economic Areas (BEAAs), Ranally Basic Trading Areas (RBTAs), and Health Care Commuting Areas (HCCAs). The three types of areas differ substantially in size, population, urbanization, and the availability of physicians. The overall percentage of physician visits outside each of the three areas was small, ranging from 3 percent for BEAAs to 5 percent for RBTAs and HCCAs. Visits by nonmetropolitan residents were about four times as likely as those by metropolitan residents to occur outside of each area. The results suggest that HCCAs are the most appropriate primary care physician service areas because they are the smallest in size and population and have the greatest variability in physician supply, yet they exhibit an amount of outside-area travel for care similar to that of the two larger types of areas.

Low income, race, and the use of mammography.

OBJECTIVE: To describe national trends in mammography use by race and income and to test whether higher use of mammography among low-income African American women than low-income white women can be explained by health insurance coverage, usual place of health care, or place of residence. DATA SOURCES/STUDY SETTING: Data from five years of the National Health Interview Survey spanning the period 1987-1994. STUDY DESIGN: Trends in the percentage of women 50-64 years of age with a mammogram within the past two years were analyzed by race and income. Data for 1993-1994 were pooled, and with logistic regression analysis, variation in use of recent mammography for low-income women was investigated. Independent variables are age, race, family income, education, health insurance coverage, place of usual source of health care, metropolitan residence, and geographic region. DATA COLLECTION/EXTRACTION METHODS: The National Health Interview Survey is a cross-sectional national survey conducted by the National Center for Health Statistics. Data are collected through household interviews. [Editor's note: in keeping with HSR policy, the term black is used to conform to its use in the surveys studied. In other references to race, the term African American is used.] PRINCIPAL FINDINGS: Among women 50-64 years of age use of recent mammograms increased rapidly between 1987 and 1991 for all groups of women, and between 1991 and 1994 the increases slowed. However, increases between 1991 and 1994 have been more rapid among low-income black women than among low-income white women. In 1993-1994, low-income black women were about one-third more likely than low-income white women to report mammography within the past two years. This difference could not be explained by health insurance coverage, usual source of health care, metropolitan status, or region of residence. CONCLUSIONS: These results, which provide some evidence of success for screening programs targeted to the poor, raise the question of why low-income black women appear to be to more likely than low-income white women to have benefited from recent efforts to promote mammography. Continued evaluation of mammography programs focused on women who are underserved as well as the monitoring of trends and variations in service use by race and income are needed.

10 years after NHANES I: mortality experience at initial followup, 1982-84.

The NHANES I Epidemiologic Followup Study (NHEFS) was initiated jointly by the National Center for Health Statistics and the National Institute on Aging in collaboration with other National Institutes of Health and Public Health Service agencies. The goal of NHEFS is to examine the relationship of baseline clinical, nutritional, and behavioral factors assessed in the first National Health and Nutrition Examination Survey (NHANES I-1971-75) to subsequent morbidity and mortality. Tracing for the initial followup began in 1981 and ended in 1984. This article compares the mortality experience of the NHEFS cohort with survival probabilities and cause-of-death distributions derived from U.S. vital statistics data. The analysis was done for 28 age-race-sex specific subgroups. The survival of each group of the NHEFS cohort corresponds quite closely to that expected on the basis of the U.S. life table survival probabilities. Mortality differentials by age, race, and sex are also quite similar between NHEFS and U.S. vital statistics. In addition, the cause-of-death distributions among NHEFS participants are quite similar to those expected based on national vital statistics. Thus, there do not seem to be any serious biases in the mortality data. The NHEFS, therefore, provides a unique resource for assessing the effects of baseline sociodemographic, health, and nutritional factors on future mortality in a large, heterogeneous sample that is representative of the nation's population.

Parental employment, family structure, and child's health insurance.

OBJECTIVE: To examine the impact of family structure on the relationship between parental employment characteristics and employer-sponsored health insurance coverage among children with employed parents in the United States. METHODS: National Health Interview Survey data for 1993-1995 was used to estimate proportions of children without employer-sponsored health insurance, by family structure, separately according to maternal and paternal employment characteristics. In addition, relative odds of being without employer-sponsored insurance were estimated, controlling for family structure and child's age, race, and poverty status. RESULTS: Children with 2 employed parents were more likely to have employer-sponsored health insurance coverage than children with 1 employed parent, even among children in 2-parent families. However, among children with employed parents, the percentage with employer-sponsored health insurance coverage varied widely, depending on the hours worked, employment sector, occupation, industry, and firm size. CONCLUSIONS: Employer-sponsored health insurance coverage for children is extremely variable, depending on employment characteristics and marital status of the parents.

The use of health service areas for measuring provider availability.

Measurement of the availability of health care providers in a geographic area is a useful component in assessing access to health care. One of the problems associated with the county provider-to-population ratio as a measure of availability is that patients frequently travel outside their counties of residence for health care, especially those residing in nonmetropolitan counties. Thus, in measuring the number of providers per capita, it is important that the geographic unit of analysis be a health service area. We have defined health care service areas for the coterminous United States, based on 1988 Medicare data on travel patterns between counties for routine hospital care. We used hierarchical cluster analysis to group counties into 802 service areas. More than one half of the service areas include only nonmetropolitan counties. The service areas vary substantially in the availability of health care resources as measured by physicians and hospital beds per 100,000 population. For almost all of the service areas, the majority of hospital stays by area residents occur within the service area. In contrast, for 39 percent of counties, the majority of hospital stays by county residents occur outside the county. Thus, the service areas are a more appropriate geographic unit than the county for measuring the availability of health care.

Medicaid-eligible children who don't enroll: health status, access to care, and implications for Medicaid enrollment.

We estimate that 17% of Medicaid-eligible children in the United States are uninsured, with 27% covered by private insurance. Uninsured children have become a target for state outreach and enrollment efforts. However, the effort may not be a worthwhile use of resources if these children have sufficient access to primary care and are able to enroll in Medicaid should serious health problems arise. This analysis of health status, access to care, and use of preventive and other services suggests otherwise. Although the uninsured Medicaid-eligible children are slightly healthier than their enrolled counterparts, they face reduced access to care and lower rates of service use. After controlling for health status and other characteristics, we find that being uninsured increases the likelihood of being without a usual source of care by eight percentage points, and increases reporting of unmet needs by seven percentage points. Being uninsured also decreases by nine percentage points the proportion of children with any health provider visits, and increases by 12 percentage points the proportion with family out-of-pocket expenses exceeding $500. These findings lend support to the hypothesis that the enrollment process is onerous for some families. Targeted efforts to enroll uninsured Medicaid-eligible children could help in reducing the effect of barriers and reducing differences in access to care.

Travel for ambulatory medical care.

This article describes travel patterns for ambulatory care based on the 1978 National Health Interview Survey. The county where a physician visit occurs has been compared with the county of patient's residence. Nearly 20 per cent of physician visits occur outside the county of residence, with substantial variation according to metropolitan status and proximity to an SMSA. Visits by nonmetropolitan residents are twice as likely to occur in another county as visits by metropolitan residents. The proportion of visits that occur outside the county of residence increases with decreasing population density, both among metropolitan and nonmetropolitan areas. Travel patterns for the usual source of care are similar to those for primary care physician visits. The results are used to estimate adjusted physician-population ratios by allocating physicians to each county type in proportion to their use by residents. These adjusted ratios exhibit substantially less variation than the unadjusted ratios.

Parental employment and health insurance coverage among school-aged children with special health care needs.

OBJECTIVES: This study examined parental employment and health insurance coverage among children with and without special health care needs. Special needs were defined as conditions likely to require a high amount of parental care, potentially affecting parental employment. METHODS: Data from the 1994 National Health Interview Survey were analyzed for 21,415 children aged 5 to 17 years, including 1604 children with special needs. Logistic regression was used to estimate the effect of special needs on the odds of full-time parental employment and on the odds of a child's being uninsured, having Medicaid, or having employer-sponsored insurance. RESULTS: Parents of children with special needs had less full-time employment. Their children had lower odds of having employer-sponsored insurance (adjusted odds ratio [OR] = 0.7) than other children. Children with special needs had greater odds of Medicaid coverage (adjusted OR = 2.3-5.1, depending on family income). Children with and without special needs were equally likely to be uninsured. CONCLUSIONS: Lower full-time employment among parents of children with special needs contributes to the children's being less likely to have employer-sponsored health insurance. Medicaid covers many children with special needs, but many others remain uninsured.

Analysis of interrupted time series mortality trends: an example to evaluate regionalized perinatal care.

Interrupted time series designs are frequently employed to evaluate program impact. Analysis strategies to determine if shifts have occurred are not well known. The case where statistical fluctuations (errors) may be assumed independent is considered, and a segmented regression methodology presented. The method discussed ia applied to the assessment of changes in local and state perinatal postneonatal mortality to identify historical trends and will be used to evaluate the impact of the North Carolina Regionalized Perinatal Care Program when seven years of post-program mortality data become available. The perinatal program region is contrasted with a control region to provide a basis for interpretation of differences noted. Relevant segmented regression models provided good fits to the data and highlighted mortality trends over the last 30 years. Considerable racial differences in these trends were identified, particularly for postneonatal mortality. Segmented regression is considered relevant for the analysis of interrupted time series designs in other applications when errors can be taken to be independent. Thus, the methodology may be regarded as a general statistical tool for evaluation purposes.

Serum albumin, coronary heart disease, and death.

To confirm a reported association between elevated serum albumin concentrations and reduced risk of death in middle-aged white men and to determine whether such associations exist for CHD incidence in white men and CHD and death in white women and black men and women, data were examined from the NHANES I Epidemiologic Follow-up Study. Over a follow-up period of 9 to 16 years, serum albumin concentrations of 4.5 gm/dl or more were associated with reduced risk of CHD incidence in white men aged 45 to 64 years (RR = 0.51; 95% CL = 0.36, 0.73) and in white women aged 45 to 74 years (RR = 0.70; 95% CL = 0.55, 0.88), independent of baseline risk factors. Independent reductions in risk of death from all causes, cardiovascular diseases, and noncardiovascular diseases were also seen in white men and women. Relative risk of death from all causes at ages 45 to 74 years in the white population was 0.73 (95% CL = 0.62, 0.85) for men and 0.71 (95% CL = 0.59, 0.85) for women. Similar reductions in risk of death from all causes and cardiovascular diseases were seen in black men and women, despite the small numbers. Further studies are needed to confirm these findings for women and black persons and to elucidate mechanisms for the effect of serum albumin.

National trends in the use of preventive health care by women.

This study investigates national changes between 1973-74 and 1985 in women's use of three preventive health services based on data from the National Health Interview Survey. Smoothed proportions of women with recent preventive care were estimated using weighted least squares for subgroups categorized by age (20-39, 40-59, 60-79), race (White, Black), income (poor, nonpoor), and year of interview. Older women and Black women experienced the largest increases in recent use of clinical breast examinations and Pap tests. Between 1973 and 1985 changes in recent breast examination ranged from zero for White women ages 20-39 years to a 23 percentage point increase (95% CI = 17,30) for Black women ages 60-79 years. A similar pattern was found for Pap testing. Changes between 1974 and 1985 in recent blood pressure testing ranged from zero for women ages 20-39 years to an 8 percentage point increase (95% CI = 6, 10) for women ages 60-79 years. Despite the increases among older women, in 1985 recent use of breast exams and Pap tests remained lower among older women. Further, the poor remained less likely than the nonpoor to have recent preventive care (except blood pressure testing among older women). Most women without recent cancer screening tests had a recent physician contact, highlighting the need for greater emphasis on cancer prevention by health care providers.