Calcium intakes and femoral and lumbar bone density of elderly U.S. men and women: National Health and Nutrition Examination Survey 2005-2006 analysis

OBJECTIVES

This analysis was aimed at assessing the benefits of total calcium intake from diet and supplements on both femoral neck and lumbar vertebral bone mineral density (BMD) in a representative sample of older U.S. women and men.

DESIGN

For 1384 women and men aged 50-70 and 71+ yr, quintiles of total calcium intake were tested for their association with hip and spine BMD after adjusting for body mass index. All data in this observational study were cross-sectional.

DATA SOURCE

Subjects included elderly residents statistically representative of the United States, women and men aged 50 yr and older in the National Health and Nutrition Examination Survey 2005-2006 cohort.

MAIN OUTCOME MEASURES

Calcium intakes and femoral and lumbar BMD were evaluated.

RESULTS

Total calcium intakes ranged from means of 400+ mg/d in quintile 1 to 2100+ in quintile 5. Little difference in hip or lumbar BMD was found in relation to total calcium consumption in women and men across five quintiles, especially for those aged 50-70, in models adjusted for body mass index only. Femoral hip BMD in men 71 and older increased slightly with high calcium intake (3.6% higher density, P = 0.0391), whereas femoral BMD in women 71 and older decreased slightly with high calcium intake (-3.2%, P = 0.0132). Lumbar BMD remained fairly consistent across all quintiles, but greater variation within each quintile was found compared with the hip.

CONCLUSIONS

A usual high calcium intake beyond the recommended dietary allowance of elderly women and men, most commonly achieved by calcium supplements, did not provide any benefit for hip or lumbar BMD. A dietary intake of calcium approaching or meeting the current recommendations was not related to higher BMD of the hip or lumbar spine in late life compared with lower intakes of calcium in older adults.

Using mixture models with linear predictors to identify incorrect gestational age in state birth records

BACKGROUND

Birthweight distributions for early last-menstrual-period-based gestational ages are bimodal, and some birthweights in the right-side distribution are implausible for the specified gestational age. Mixture models can be used to identify births in the right-side distribution. The objective of this study was to determine which maternal and infant factors to include in the mixture models to obtain the best fitting models for New Jersey state birth records.

METHODS

We included covariates in the models as linear predictors of the means of the component distributions and the proportion of births in each component. This allowed both the means and the proportions to vary across levels of the covariates.

RESULTS

The final model included maternal age and timing of entry into prenatal care. The proportion of births in the right-side distribution was lowest for older mothers who entered prenatal care early, higher for teen mothers who entered prenatal care early, higher still for older mothers who entered prenatal care late, and highest for teens who entered prenatal care late. Over 44% of births were classified as incorrect reported gestational age.

CONCLUSION

These results suggest that (1) including these two covariates as linear predictors of the means and mixing proportions gives the best model for identifying births with incorrect reported gestational age, (2) late entry into prenatal care is a mechanism by which erroneously short last-menstrual-period-based gestational ages are generated, and (3) including linear predictors of the mixing proportions in the model increases the validity of the classification of incorrect reported gestational age.

Micronutrient intakes in two US populations of older adults: lipid research clinics program prevalence study findings

Dietary intakes of several minerals and vitamins were assessed in two US sub-populations of older men and women between 60 and 80 years as part of the Lipid Research Clinics Program Prevalence Study conducted in the mid-1980s prior to widespread fortification. Dietary intakes were analyzed from 24-hour recalls using the Minnesota Nutrition Coding Center. Descriptive statistics on the two diverse sub-populations were generated for the elderly subjects at the two clinic sites, southern California and Oklahoma. Regression analyses of specific micronutrients were performed while controlling for several variables, namely, age, sex, clinic (region), education, Body Mass Index (BMI), alcohol consumption, and smoking status. Compared to current (1999-2004) Estimated Average Requirements (EARs) and Adequate Intakes (AIs) for three micronutrients without EARs for the US and Canada, several micronutrients were consumed at or close to their EAR values. Exceptions include intakes of vitamin A, vitamin E, folic acid, potassium and calcium which were very low; intakes of thiamin, riboflavin, niacin, and vitamin C were low but closer to the published EAR or AI values. High intakes approaching cut-offs for practically all subjects were found for both groups of elders at the two clinic sites for iron, phosphorus, and sodium. In general, California elderly had somewhat better consumption patterns for the vitamins, but the Oklahomans, males at least, had higher overall mineral intakes. The micronutrient deficits found in this small study suggest that most elderly US citizens were likely to be deficient in five micronutrients and marginally insufficient in four others in the mid-1980s and, despite even greater fortification currently, elderly intakes seem not to have improved substantially since the 1980s, except for subjects who are regular multi-supplement users.

The multistate life table method: an application to contraceptive switching behavior

In many demographic behaviors (e.g., those relating to marriage, contraception, migration, and health), people change among multiple statuses through time, sometimes leaving and then returning to the same status. Data on such behaviors are often collected in surveys as censored event histories. The multistate life table (MSLT) can be used to properly describe, in a single analysis, these complex transitions among multiple states measured in such data, but MSLT is rarely applied in the demographic literature because practical guidance is lacking on how to compute MSLTs with such data. We provide methods for computing MSLT quantities using censored event-history data: namely, transition intensities and probabilities, "state occupancy" probabilities and standard errors, average time spent in specified states, and average number of visits to specified states. Applying these methods to contraceptive use, we find high levels of switching back and forth, particularly between barrier methods and non-use, resulting in high rates of unintended pregnancy.

Macronutrient intakes of elderly in the Lipid Research Clinics Program Prevalence Study

As part of the Lipid Research Clinics (LRC) Program Prevalence Study of coronary heart disease risk factors, nutrient intakes of two US populations over 59 years of age were determined by 24-hour recalls in the 1970s. Characteristics of the populations were (1) California: suburban, upper-middle class, 95% high school graduates, 10% blue collar occupations; (2) Oklahoma: rural lower-middle class, 75% high school graduates, and 40% blue-collar occupations. Macronutrients consumed by both populations were similar, except for alcohol. For both men and women, energy intake was approximately 25 kcal/kg/day (body weight) sources of energy were approximately 40% from carbohydrate, 16% from protein, 37% from fat, and 4% from alcohol. The Oklahoma population, however, consumed significantly less alcohol than did Californians. Percentages of calories from fatty acids were approximately 14% from saturated and 6% from polyunsaturated, which yielded a polyunsaturated: saturated ratio of 0.48. The intake of cholesterol for women was 190 mg/1000 kcal and for men, 210 mg/1000 kcal. Between the ages of 60 and 69, the Oklahoma men consumed more energy than did the California men. Both sexes demonstrated lower energy intakes with advancing age and with increasing body mass index. The higher energy intake of the Oklahoma cohort aged 60-69 was attributed to the greater physical demands of their occupations, but this difference disappeared after age 70. The California and Oklahoma women had similar caloric intakes beyond age 60. In summary, the LRC findings suggest that geographically diverse American populations consumed in the late 1970s remarkably similar intakes of macronutients and cholesterol, with the only major exception being energy from alcoholic beverages.

Some analytical models to estimate maternal age at birth using age-specific fertility rates

"A class of analytical models to study the distribution of maternal age at different births from the data on age-specific fertility rates has been presented. Deriving the distributions and means of maternal age at birth of any specific order, final parity and at next-to-last birth, we have extended the approach to estimate parity progression ratios and the ultimate parity distribution of women in the population.... We illustrate computations of various components of the model expressions with the current fertility experiences of the United States for 1970."

Influences of mother's work, childhood place of residence, and exposure to media on breast-feeding patterns: experience of Nigeria and Uganda

This study uses data from the Nigerian Demographic and Health Survey collected in 1990 and the Ugandan Demographic and Health Survey collected in 1995 to examine the implications of mother's work, childhood place of residence, and exposure to the media for breast-feeding patterns (exclusivity and intensity) in Nigeria and Uganda. Nigeria and Uganda present an interesting contrast because Nigeria is more modernized and economically developed than Uganda, thus providing a good indication of the influence of modernization on breast-feeding patterns. Mother's work status is defined by considering whether mothers earned cash from work and took their children to work, hence emphasizing the compatibility of work with child care. Work least compatible with child care had a negative effect on breast-feeding intensity in Nigeria. The negative effect of mother's work on exclusive breast-feeding (that is, if the mothers used formula or milk instead) observed for some working mothers in Nigeria and Uganda was partly confounded by urban residence, exposure to media, and other socioeconomic factors. Mother's work did not have a negative effect on breast-feeding intensity in Uganda. The relationship between mother's work, urban residence, media exposure, and breast-feeding practice seems to be stronger in Nigeria than Uganda.

Using the overdispersed exponential family to estimate the distribution of usual daily intakes of people aged between 18 and 28 in Taiwan

Assessment of usual dietary intake of a population is essential to understand the nutrition status of the population. Methods like 24-hour dietary recall and food records are commonly used for this task. However, within-individual variation exists in the food record data. Methods considering measurement errors have been used to evaluate the association between nutrient intakes and diseases. Few have been devoted to estimating the distribution of usual daily intakes. This paper proposes applying the formulation of the overdispersed exponential family to estimate the distribution of usual nutrient intake and applies the adjustments developed by Liu to reduce the variance of the distribution. The proposed method has the advantages of working on the original scale of data and implementation convenience. The adjustment of the variance is carried out by dividing the variance into within-individual variance and among-individual variance. The adjusted variance, then, is used to estimate the distribution of the usual daily intake. Sampling weights are considered in all the steps, except the estimation of the ratio of within to among variance. The data for this study are from the Nutritional and Health Survey in Taiwan conducted between 1993 and 1996 (NAHSIT, 1993-1996). An independent external set of data for people aged between 18 and 28 years (49 males and 20 females) is used to estimate the ratio of within to among individual variance. Due to the availability of data in estimating the ratio of within to among individual variance, 430 males and 422 females in the NAHSIT sample are used to estimate the distribution of usual daily intakes for people aged between 18 and 28 in Taiwan. The distribution also allows us to estimate the proportion of people who do not meet the recommended daily nutrient allowance (RDNA). The results show that the intakes of calcium and vitamin E of this group of people fall far below RDNA.

The paucity of effects in community trials: is secular trend the culprit?

BACKGROUND

The most recent major U.S. trials that evaluated community-level programs to influence risk factors and health behaviors identified secular trends in the risk factors and health behaviors among the factors that might have limited community-level effects. The research reported in this paper uses data from one of the trials to examine the secular trend explanation directly.

METHODS

Data from the 22-community Community Intervention Trial for Smoking Cessation (COMMIT) were analyzed to test a hypothesis based on secular trend reasoning: program effects for smoking prevalence were larger for treatment communities matched to control communities with small declines in smoking than in treatment communities matched to control communities with larger declines in smoking.

RESULTS

Consistent with the secular trend explanation, program effects were larger when control communities had relatively small declines in smoking prevalence.

CONCLUSIONS

The findings suggest that secular trends masked community-level program effects in COMMIT.

Risk factors for horizontal transmission of hepatitis B virus in a rural district in Ghana

Most hepatitis B virus (HBV) infections in sub-Saharan African infants and children are acquired through horizontal transmission, but the exact mechanisms of spread have not been documented. The authors conducted a study in rural Ghana which determined seroprevalence in a probability sample of 1,385 individuals of all ages, and evaluated risk factors for horizontal transmission of HBV in a subsample of 547 children aged 1-16 years who were not hepatitis B surface antigen (HBsAg) carriers. Most residents in this district live in compounds which typically contain 2-4 households each. Overall prevalence of HBV seropositives (any HBV marker) was 74.7% (95% confidence interval (CI) 72.5%-76.9%). Prevalence of HBsAg was 20.9% (95% CI 18.8%-23.1%). The data suggest a continuous nonuniform acquisition of HBV infection with advancing age predominantly through horizontal transmission in childhood, with the household, rather than the domestic compound, being the primary place for transmission. The behaviors most strongly associated with prevalence of HBV were sharing of bath towels (OR = 3.1, 95% CI 2.1-4.5), sharing of chewing gum or partially eaten candies (OR = 3.4, 95% CI 2.3-5.0), sharing of dental cleaning materials (OR = 2.5, 95% CI 1.3-4.6), and biting of fingernails in conjunction with scratching the backs of carriers (OR = 2.5, 95% CI 1.6-4.3).

Analysis of contraceptive discontinuation in six developing countries from durations of use at survey

We conduct a cross-national study of contraceptive discontinuation among currently married nonsterilized contracepting women in Bolivia, Egypt, Kenya, Sri Lanka, Thailand, and Zimbabwe using the Demographic and Health Surveys (DHS). Since the DHS contains no true completed epochs of contraceptive use, the distribution of use times at survey is used to approximate the distribution of the completed epochs using the renewal theorem. Two techniques based on this approximation are used. The first technique uses local linear regression smoothing of a histogram estimate of the use time at survey pdf which is converted into an estimate of the discontinuation probability function. The second technique poses a proportional hazards Weibull distribution for the discontinuation probability function which is then converted into a model for the use times at survey. This second technique is used to model the observed variations in use across countries while controlling for other sociodemographic factors such as children ever born, age, and education, as well as a variable which encodes knowledge of the fertility cycle. Pill discontinuation probabilities range from 0.12 to 0.47 in the first year. IUD discontinuation probabilities range from 0.18 to 0.53 in the first year. Discontinuation probabilities in Egypt over all methods are in agreement with those reported in Ali and Cleland (1995). Logged relative risks of pill discontinuation range from -0.94 (Sri Lanka) to 0 (Kenya), while logged relative risks of IUD discontinuation range from -0.53 (Sri Lanka) to 0.41 (Zimbabwe). The ordering of risks of pill discontinuation among the six countries considered is in agreement with the ordering of total fertility rates excerpted from Westoff (1991).

Sudden infant death syndrome and local meteorologic temperature in North Carolina

The association between meteorologic temperature and sudden infant death syndrome was investigated in the 1982-1983 North Carolina birth cohort. Maximum daily temperatures recorded at weather stations in the subject's county of residence for each day of the first year of life were entered into hazards models as time-dependent covariates. Risk ratios for a maximum temperature of < or = 53 degrees F (12 degrees C) 5 days before the event compared with a maximum temperature of > 53 degrees F were 2.3 (95% confidence interval 1.6-3.3) for blacks and 1.5(95% confidence interval 1.0-2.1) for whites. Similar results were found for minimum daily temperature. The analysis controlled for season of birth, sex, maternal age, maternal education, parity, and birth weight.

The National Epidermolysis Bullosa Registry

Since its inception in 1986, the NEBR has proved to be an excellent example of how a relatively small allocation of federal research funds for the development of a registry of cases of a single rare disease can have a major impact on the rapid expansion in the depth of knowledge of not only the disease itself but of a number of associated biologic principles, including keratinization and epithelial cell-extracellular matrix interactions. At present, the NEBR is generating extensive clinical, laboratory, and demographic data, both from cross-sectional and longitudinal perspectives, as well as establishing a centralized cell and tissue bank that will serve the scientific community at large as a valuable resource for future basic research on this oftentimes devastating genetic disease.

Smoothed breastfeeding durations and waiting time to conception

Breastfeeding beyond the resumption of mother's menstruation plays a significant role in the proximate determinants of fertility. Breastfeeding and postpartum amenorrhoea data collected from retrospective surveys usually exhibit digit preferences. Here, these heaping errors were smoothed by B-spline and used in multivariate models of risk of conception to investigate the contraceptive effect of breastfeeding. The data used come from a 1987 Indian survey. Results show that lactation, after mother's menses resume, reduces the risk of conception. Heaping in breastfeeding data attenuates this relationship. When adjustment is made, breastfeeding reduced the rate of conception by 47 per cent; the reduction, with adjusted data, was 63 per cent.

Plasma triglyceride level and mortality from coronary heart disease

BACKGROUND

Whether the plasma triglyceride level is a risk factor for coronary heart disease has been controversial, and evaluation of the triglyceride level as a risk factor is fraught with methodologic difficulties.

METHODS

We studied the association between plasma triglyceride levels and the 12-year incidence of death from coronary heart disease in 10 North American populations participating in the Lipid Research Clinics Follow-up Study, while adjusting for the potential confounding effects of other risk factors for cardiovascular disease, including the level of high-density lipoprotein (HDL) cholesterol. All analyses were sex-specific, and separate analyses were performed in high and low strata of HDL cholesterol, low-density lipoprotein (LDL) cholesterol, fasting plasma glucose, and age.

RESULTS

The rates of coronary death in both men and women increased with the triglyceride level. In Cox proportional-hazards models adjusted for age, in which the natural log of the triglyceride levels was used to give a normal distribution, the relative risk per natural-log unit of triglyceride (e.g., a triglyceride level of 150 mg per deciliter vs. a level of 55 mg per deciliter) was 1.54 (95 percent confidence interval, 1.19 to 1.98; P < 0.001) in men and 1.88 (95 percent confidence interval, 1.19 to 2.98; P < 0.007) in women. After an adjustment for potential covariates, however, these relative risks were not statistically significant. Analyses based on lipoprotein cholesterol levels revealed a positive association between the triglyceride level and coronary mortality in the lower stratum of both HDL and LDL cholesterol, but not in the higher stratum. Conversely, the HDL cholesterol level was unrelated to coronary mortality in the lower stratum of LDL cholesterol, but was strongly inversely associated with coronary death in the higher stratum of LDL cholesterol. The relative risk of coronary death associated with triglyceride level was higher at younger ages. The associations between the triglyceride level and coronary mortality in the lower HDL cholesterol, LDL cholesterol, and age strata were small and were further reduced by an adjustment for the fasting plasma glucose level.

CONCLUSIONS

Overall, the plasma triglyceride level showed no independent association with coronary mortality. However, in subgroups of subjects with lower HDL and LDL cholesterol levels and in younger subjects, defined a priori, an association between the triglyceride level and coronary mortality was observed, although this association was small and was not statistically significant after an adjustment for the plasma glucose level.

Analysis of birth intervals in India's Uttar Pradesh and Kerala States

Life tables of birth intervals and median birth intervals in two Indian states, Uttar Pradesh and Kerala, were computed for several subgroups of the study population. Multivariate hazards modelling technique was used to examine the net effect of each of the variables studied. The results show a substantial effect of socioeconomic variables in child-spacing after controlling for the major intermediate variables.

Estimation of fecundity and secondary sterility from survey data on birth intervals in Egypt

Data on the last closed and open birth intervals have been used to ascertain the current potential of childbearing for women in terms of estimating fecundity and secondary sterility by age, residence, and educational subgroup. Under the assumption that after a specific period from the last birth a certain proportion of women become secondarily sterile, we propose and apply an inflated model of open birth interval to obtain the proportion of women who are secondarily sterile. The data used for the analysis are extracted from the Egyptian Fertility Survey conducted in 1980.

Effects of breast feeding after resumption of menstruation on waiting time to next conception

We investigate the association between breast feeding after resumption of menstruation and the duration from resumption of menses to the next conception. Data from a survey, "Breast-Feeding and Its Effect on Fertility," conducted in 1987 under the auspices of the Centre of Population Studies, Banaras Hindu University, India, were used. We used hazard models of conception rates after the return of menstruation with breast-feeding duration as a time-dependent covariate. The interaction of breast-feeding duration after resumption of menses and postpartum amenorrhea have a significant effect on the rate of conception after return of menses. After resumption of menstruation, when there is no breast feeding, the risk of conception increases with the increase in postpartum amenorrhea. However, breast feeding attenuates the effects of postpartum amenorrhea. These results suggest that breast feeding beyond the resumption of menstruation plays a significant role in the proximate determinants to reduce fertility.

Age and season of birth in sudden infant death syndrome in North Carolina, 1982-1987: no interaction

Sudden infant death syndrome (SIDS) is a major cause of death in the postneonatal period. SIDS peaks in the winter and at age 3 months. The hypothesis that season and age interact to determine SIDS survival was tested in race-specific hazards models that included an interaction term for season of birth and survival time. The study population was the 1982-1984 and 1985-1987 North Carolina birth cohorts. The interaction term had null effect in all models, indicating that season and age are independent determinants of SIDS survival. These results may be confounded by exposure to cigarette smoke, for which no data were available.

Age at last birth and its components

This paper examines the ways in which the behavior of twentieth century cohorts of American women changed simultaneously in the three components of fertility that determine age at last birth--age at first birth, spacing between subsequent births, and parity progression ratios of subsequent births--to produce changes in the timing of the completion of childbearing. It decomposes changes in the mean age at last birth among cohorts and between whites and nonwhites to changes in these three components. To perform these analyses, we developed and applied a method to estimate the distributions and means of ages and last births, birth intervals, and parity progression ratios from age- and parity-specific fertility rates available from vital statistics data. Results show that the cohorts increased and decreased their age at first birth, birth intervals, and parity progression ratios of lower and higher birth orders in almost every possible combination so as to achieve a relatively young age at final birth.

Characteristics of maternal employment during pregnancy: effects on low birthweight

BACKGROUND

Although maternal employment is considered a risk factor for low birthweight (LBW), the manner in which employment might affect birthweight is poorly understood. In this analysis, selected characteristics of employment during pregnancy were examined for effects on pregnancy outcomes.

METHODS

Work characteristics included the number of hours per week, physical activities, and environmental conditions. The outcomes of interest were fetal growth retardation (less than 2500 grams at term) and preterm delivery (less than 37 weeks). The study population consisted of 2711 non-Black, married mothers who participated in the 1980 National Natality Survey (NNS). The NNS data were merged with data from the 1977 revision of The Dictionary of Occupational Titles (DOT) from which measures of occupational physical activities and environmental exposures were obtained. Logistic regression was used in the analysis.

RESULTS

Those who worked 40 or more hours per week were more likely than women who worked fewer hours to have a low birthweight delivery at greater than or equal to 37 weeks. No physical or environmental characterics of work were associated with low birthweight or preterm delivery.

CONCLUSIONS

Non-Black married American women may face a risk of delivering low-birthweight babies at or near term only if they work 40 or more hours each week. However, the lack of risk associated with other characteristics of work may be a function of measurement error in the DOT data source or of low levels of exposure in the analysis population.

Ten-year mortality from cardiovascular disease in relation to cholesterol level among men with and without preexisting cardiovascular disease

To determine the associations of total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol with mortality from coronary heart disease and cardiovascular disease, we studied 2541 white men who were 40 to 69 years old at base line and followed them for an average of 10.1 years. Seventeen percent had some manifestation of cardiovascular disease at base line, whereas the others did not. Among the men who had cardiovascular disease at base line, we found, after multivariate adjustment, that those with "high" blood cholesterol levels (above 6.19 mmol per liter) had a risk of death from cardiovascular disease, including coronary heart disease, that was 3.45 times higher (95 percent confidence interval, 1.63 to 7.33) than that for men with "desirable" blood cholesterol levels (below 5.16 mmol per liter). The corresponding hazard ratios were 5.92 (95 percent confidence interval, 2.59 to 13.51) for LDL cholesterol levels above 4.13 mmol per liter as compared with those below 3.35 mmol per liter, and 6.02 (95 percent confidence interval, 2.73 to 13.28) for HDL cholesterol levels below 0.90 mmol per liter as compared with those above 1.16 mmol per liter. All three lipid levels were also significant predictors of death from coronary heart disease alone (P less than 0.005). Total cholesterol and LDL cholesterol levels were also significant predictors of death from cardiovascular and coronary heart disease in men without preexisting cardiovascular disease, although at a lower level of absolute risk of death. Thus, the 10-year risk of death from cardiovascular disease for a man with preexisting cardiovascular disease increased from 3.8 percent to almost 19.6 percent with increasing levels of total cholesterol from "desirable" to "high," whereas the corresponding risk for a man who was free of cardiovascular disease at base line increased from 1.7 percent to 4.9 percent. Our findings suggest that total, LDL, and HDL cholesterol levels predict subsequent mortality in men 40 to 69 years of age, especially those with preexisting cardiovascular disease.

Black-white differences in exercise blood pressure. The Lipid Research Clinics Program Prevalence Study

After exclusion of persons on blood pressure medication or with prevalent cardiovascular disease, we studied 83 black and 2,548 white men and 113 black and 1,519 white women 20-69 years old from the Lipid Research Clinics population sample who had performed a standardized treadmill exercise test. Resting systolic and diastolic blood pressures were similar in black and white men, but the diastolic pressure was significantly higher in black than in white women (81.4 vs 77.4 mm Hg). Body weight was higher in black than in white women, and reported physical activity was higher in black than in white men. The proportion of smokers was somewhat higher in blacks than in whites. During the treadmill exercise test with a modified Bruce protocol, mean systolic blood pressure at stage 2 was 174 mm Hg in black men and 166 mm Hg in white men (p less than 0.02), but stage 2 blood pressures did not differ between black and white women (153 and 152 mm Hg, respectively). Even after adjustments were made for levels of baseline characteristics (age, weight, resting systolic blood pressure, smoking, low density lipoprotein cholesterol, physical activity, and alcohol intake), black men responded with a 7-mm Hg higher systolic blood pressure during exercise than white men (p less than 0.01). Another new finding was a highly significant positive association between stage 2 systolic blood pressure and low density lipoprotein cholesterol in men. The findings suggest a higher systemic vascular resistance during exercise in the selected sample of black men, which is consistent with the higher incidence of hypertension in black men.

Statistical modeling of selected aspects of the childbearing process with application to World Fertility Survey countries

"A mathematical model for estimation of certain aspects of the childbearing process, which requires only data on age-specific fertility rates, is developed. Synthetic maternal childbearing indices, namely, mean ages at first and last birth, length of reproductive life span, inter-birth spacing, and proportion of childless women, in addition to the well-known mean age at childbearing, for the WFS [World Fertility Surveys conducted in developing] countries are obtained using the proposed model. The indices are free from age truncation effects, and, under certain assumptions, provide information about a cohort's completed fertility before the women stop reproducing. The effects of women's residence and education on fertility are also examined." (SUMMARY IN FRE)

Coronary heart disease morbidity and mortality in hypercholesterolemic men predicted from an exercise test: the Lipid Research Clinics Coronary Primary Prevention Trial

A positive exercise electrocardiogram (ECG) has been proved to predict cardiovascular events in asymptomatic normolipidemic men. To study whether it is also predictive for hypercholesterolemic men, data from 3,806 asymptomatic hypercholesterolemic men in the Lipid Research Clinics Coronary Primary Prevention Trial were analyzed. All the men had performed a submaximal treadmill exercise test at baseline, before they were assigned to the cholestyramine or placebo treatment group. Because of missing or inconclusive data, 31 men were excluded from the analyses. A test was positive if the ST segment was displaced by greater than or equal to 1 mm (visual code) or there was greater than or equal to 10 microV-s change in the ST integral (computer code), or both. The prevalence of a positive test was 8.3%. During the 7 to 10 year (mean 7.4) follow-up period, the mortality rate from coronary heart disease was 6.7% (21 of 315) in men with a positive test and 1.3% (46 of 3,460) in men with a negative test (placebo and cholestyramine groups combined). The age-adjusted rate ratio for a positive test, compared with a negative test, was 6.7 in the placebo group and 4.8 in the cholestyramine group. With use of Cox's proportional hazards models, it was found that the risk of death from coronary heart disease associated with a positive test was 5.7 times higher in the placebo group and 4.9 times higher in the cholestyramine group after adjustment for age, smoking history, systolic blood pressure, high density lipoprotein cholesterol and low density lipoprotein cholesterol. A positive test was not significantly associated with nonfatal myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Male infertility in inflammatory bowel disease

We examined fertility in men with inflammatory bowel disease (IBD) to determine whether the reported deficit in pregnancies in their spouses was due to reduced reproductive capacity. The cases were 106 men with Crohn's disease and 62 with ulcerative colitis drawn from the rosters of North Carolina chapters of the National Foundation for Ileitis and Colitis. The 140 normal controls were neighbors identified by the cases. There were 186 pregnancies among the spouses of men with Crohn's disease, 110 among the ulcerative colitis group, and 300 among the controls. The mean number of pregnancies among the Crohn's disease patients (1.75 +/- 0.12) was significantly lower than the number for controls (2.14 +/- 0.11), p less than 0.02. The reduction in the mean number of pregnancies among patients with ulcerative colitis (1.77 +/- 0.18) was not significantly different from controls (p less than 0.07). Analysis of waiting time to conception showed that fecundability (the probability of pregnancy in a menstrual cycle) was not different in spouses of IBD patients and controls. We conclude that the overall reproductive capacity of men with IBD is not markedly diminished.

Heterogeneous risk models

"This paper briefly reviews the heterogeneous risk models in demography. With a specific model, it is shown that in a heterogeneous population, the marginal hazard need not be monotonic. Procedures described in the literature to recover individual hazards from marginal hazards without precise knowledge of structural parameters can lead to biased results. Strategies of parameter estimation and testing are discussed. The results are extended to [the] multistate life table."

Maternal age at last birth in Egypt

A proportional hazards regression model was applied to data on women aged 45–49 from the Egyptian Fertility Survey, to assess the effects of women's education, residence, and marital experience on their age at the birth of their last child. When age at marriage and parity were controlled, well-educated urban women tended to stop reproducing earlier than less educated rural women. Compared to intact first marriages, marital dissolution (divorce, widowhood, or separation) with remarriage tended to prolong the age at last birth, while failure to remarry tended to hasten it.

Cardiovascular mortality and noncontraceptive use of estrogen in women: results from the Lipid Research Clinics Program Follow-up Study

A cohort of 2270 white women, aged 40-69 years at baseline, were followed for an average of 8.5 years in the Lipid Research Clinics Program Follow-up Study. There were 44 deaths due to cardiovascular disease among the 1677 nonusers of estrogens and six cardiovascular disease deaths among the 593 estrogen users. The age-adjusted relative risk (RR) of cardiovascular disease deaths in users compared with nonusers was 0.34 (95% confidence limits 0.12 to 0.81). After multivariable adjustment for potential confounding factors (age, blood pressure, and smoking), the estimated RR for estrogen use was 0.37 (95% confidence limits 0.16 to 0.88). Analyses were done to explore whether these results could be due to selection bias for estrogen use. However, the prevalence of cardiovascular disease at baseline was slightly higher in estrogen users (12%) than in nonusers (10%); furthermore, the exclusion of all women with prevalent cardiovascular disease at baseline did not alter the apparent protective effect of estrogen use on cardiovascular disease mortality (RR = 0.42, 95% confidence limits 0.13 to 1.10). Additional analyses examining the complex association between estrogen use, lipoprotein levels, and cardiovascular disease mortality suggest that the protective effect of estrogen is substantially mediated through increased high-density lipoprotein levels.

Customary diet, anthropometry, and dyslipoproteinemia in selected North American populations. The Lipid Research Clinics Program Prevalence Study

The intake of nutrients, determined by 24 hr diet recall, and body measurements were obtained in 8250 free-living white study participants divided into 20 to 49 and 50 + age groups for males and female nonusers and users of gonadal hormones. They were classified into dyslipoproteinemia (DLP) phenotypes: hyperHDL, hypoHDL, IIA, hpypoLDL, IV, and normal. The dyslipoproteinemia DLP phenotypes, compared with the normal, had biologically meaningful differences in nutrient intake and indexes of obesity that were most marked for males aged 20 to 49 years as shown in the table (below). Those with the hyperHDL phenotype were thinner and ingested more energy and more alcohol and less carbohydrate as percent kilocalories (%kcal). Individuals classified as hypoHDL were fatter and tended to ingest less energy and less alcohol as %kcal. Persons with the type II phenotype were fatter and ingested less energy. Those with hypoLDL tended to be thinner and ingested more energy. Individuals with the type IV phenotype were fatter, ingested less energy and carbohydrate and more alcohol as %kcal. Similar trends were observed in female nonusers of hormones aged 20 to 49 and to a lesser extent in the 50 + age groups and in female users of hormones. Dietary protein, cholesterol, total fat, and polyunsaturated and saturated fatty acids had no consistent associations with DLP phenotype, and sucrose and starch had no association independent of total carbohydrate. This is the first evidence of an association of customary diet and DLP phenotypes in the free-living population. Equating energy intake with energy expenditure, persons with the high-risk phenotypes, IIA, IV, and hypoHDL, compared with the normal, had decreased energy expenditure and were fatter, whereas those with the low-risk phenotypes, hyperHDL and hypoLDL, had increased energy expenditure and were thinner.

Progeny's lipid and lipoprotein levels by parental mortality. The Lipid Research Clinics Program Prevalence Study

Using data from Lipid Research Clinics study participants at visit 2 (3972 and 2346 adult men and women), we examined the hypothesis that parental mortality from cardiovascular disease (CVD) or cancer before age 60 predicts their adult progeny's lipid and lipoprotein levels. Weighted regression analysis was used to control for the potential effect of progeny's other CVD risk factors (age, systolic blood pressure, Quetelet index, cigarette smoking, and alcohol consumption), and to assess for the effect of progeny's parental cause-specific mortality status on progeny's lipids and lipoproteins. Nearly all of the statistically significant parent-progeny predictions were for sons. Paternal death from CVD before age 60 years was associated with significantly higher plasma total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels in sons and (at marginal significance) in daughters, when compared with those in reference progeny with paternal survival over age 60 or over age 75. Maternal death from CVD before 60 was associated with lower levels of high-density lipoprotein cholesterol (HDL-C) in sons. Paternal and maternal death from cancer before age 60 years were associated with higher triglyceride levels in adult sons than in sons whose parents had lived beyond ages 60 and 75. Paternal all-cause mortality before age 60 was associated with higher cholesterol and triglycerides in sons; maternal all-cause mortality before age 60 was associated with depression of HDL-C in sons. Familial aggregation of lipids and lipoproteins may account, in part, for familial aggregation of CVD. Knowledge of family history facilitates identification of progeny at higher risk for CVD by virtue of elevated cholesterol or LDL-C, or reduced HDL-C.

Dyslipoproteinemia in black participants. The Lipid Research Clinics Program Prevalence Study

A comparison of blacks and whites 6 to 49 years old revealed striking differences between races with respect to the prevalence of various dyslipoproteinemias and mean plasma lipid levels. Compared with whites, juvenile and adult blacks of both sexes had higher mean levels of high-density lipoprotein cholesterol (HDL-C), with correspondingly higher prevalences of the hyperHDL and hypoLDL (low-density lipoprotein) phenotypes. In contrast, whites showed a much higher prevalence of type IV hyperlipoproteinemia and higher mean triglyceride levels in most age-sex groups. Although juvenile blacks had higher mean levels of LDL-C than did whites, this race difference was reversed in men, while women showed inconsistent differences between races. Adult black men and juvenile blacks of both sexes had a somewhat higher prevalence of the type IIA phenotype than whites. The distribution of major HDL-C predictors in this population could not account for the difference in prevalence of hyperHDL between races. These findings suggest that health professionals may find differences in plasma lipid and lipoprotein patterns between their black and white patients, but additional research is needed to ascertain the disease risks associated with dyslipoproteinemia among blacks.

Factors affecting infant and child mortality

This paper examines the determinants of infant and child mortality variations in four near east countries using data from WFS surveys. The analysis considers biological correlates of mortality—mother's age, birth order, birth interval, and previous infant loss—and several social factors—mother's and father's education, mother's residence, father's occupation, and mother's work experience since marriage. A multivariate analysis using a logistic regression model is carried out to obtain the net effect of each factor on mortality. Separate models are constructed for infant mortality and childhood mortality and for each country.

The four countries show large variations in mortality, but this is persistently higher in female than male children. All four demographic characteristics affect mortality significantly, especially the length of the preceding birth interval. Among the socioeconomic variables, only rural–urban residence is influential.

Demographic, behavioral, biochemical, and dietary correlates of plasma triglycerides. Lipid Research Clinics Program Prevalence Study

Few studies have simultaneously examined the relationship of triglyceride levels with a wide variety of potential covariates. Thus, the present study was designed to assess in a large, free-living population the association of fasting plasma triglyceride values with selected demographic, behavioral, biochemical, and dietary measures. These analyses were done using data obtained from 5189 white men and women aged 20 to 69 years who participated in the Lipid Research Clinics Program Prevalence Study. Of the eight nondietary factors examined, age, Quetelet Index, fasting plasma glucose, and cigarette smoking were strongly, positively associated (p less than 0.0001) with triglycerides in men and in women not using gonadal hormones. Among women using oral contraceptives or estrogens, only Quetelet Index (p less than 0.01) and cigarette smoking (p = 0.01) were significantly related to triglyceride values. Physical activity was inversely associated (p less than 0.0001) and use of diuretic medications was positively related (p less than 0.01) to triglycerides only in men. Results of analyses of triglycerides and six selected dietary measures varied by age, sex, and hormone-use subgroups. Although none of the dietary variables showed consistent associations with triglycerides across all of the subgroups, triglycerides tended to be inversely associated with total calories per kilogram of body weight and the percentage of calories as dietary fat.

Childbearing and family in remarriage

Proportional hazards models are used to test hypotheses about the effect of women’s prior childbearing on the probability of having a birth in remarriage and to analyze the effects of other factors. Results indicate that the number of children at the time of remarriage has no effect on childbearing probabilities, but the age of the youngest child has a significant effect. These findings support the view that having a child is important to confirm the marriage, but that individual and family life course factors also affect the decision to have a child in a remarriage.