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Results for “Intermediate Variables”

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At least 19 recordsLinked to original sources
PubMed1996

Fructose-1,6-bisphosphatase. Primary structure of the rabbit liver enzyme. 'Intermediate' variability of an oligomeric protein.

The primary structure of rabbit liver fructose-1,6-bisphosphatase was determined by peptide analysis of digests with different proteases. The results establish the primary structure, complete data bank entries, and show that this enzyme variant is indeed homologous with other liver fructose-1,6-bisphosphatases. Residue differences with the enzymes from other mammals are 9-15%, with those from plants and yeasts about 50%, and with those from characterized prokaryotes up to 70%, showing an enzyme variability intermediate between those of 'variable' and 'constant' oligomeric dehydrogenases. Structural relationships, conformations and catalytic mechanisms are consistent within the family of fructose-1,6-bisphosphatases, and the rabbit protein is a typical rather than an aberrant form of the enzyme.

Adenosine Monophosphate↗
PubMed1998

Causal pathways to infant mortality: linking social variables to infant mortality through intermediate variables.

Using a conceptual model that integrates social and biomedical models of causation, this paper delineates the pathways through which social factors ultimately influence infant mortality in the African-American community. Two social factors, maternal education and marital status, are shown to influence the risk of infant death through the following intermediate variables: bio-demographic (maternal age, birth order, birth interval and outcome of last pregnancy), health care (prenatal care utilization) and proximate infant health status at birth (preterm delivery and low birth weight). While the impact of maternal education is largely explained by the intermediate variables, marital status remains a significant, albeit a weak, predictor net of all other variables.

Black or African American↗
PubMed1982

Intermediate variables and educational differentials in fertility in Korea and the Philippines.

This analysis compares the effects of contraceptive use and infant and fetal mortality on the pace of fertility in Korea and the Philippines and explores the mediating effects of these intermediate variables on educational differentials in childspacing. For both intervals initiated in a recent period before a sample survey, second, third and higher-order intervals are examined. Transitions within successive segments of interval exposure (qx values) are examined rather than cumulative transitions (1 - lx values). This methodological choice is substantively important because breastfeeding should primarily affect early segments of exposure and because it allows empirical examination of the timing of the effects of other variables such as contraceptive use. Further, this choice allows multivariate analysis within the structure of the life-table perspective. The results show substantial differences in patterns between Korea and the Philippines, indicate clearly the effect of each intermediate variable, and illustrate how educational differentials in fertility are affected by contraception and infant and fetal mortality.

Adult↗
PubMed1989

The control of confounding by intermediate variables.

In epidemiologic studies of the effect of an exposure on disease, the crude association of exposure with disease may fail to reflect a causal association due to confounding by one or more covariates. Most previous discussions of confounding in the epidemiologic literature have considered only point exposure studies, that is, studies that measure exposure and covariate status only once, at start of follow-up. In this paper we offer definitions of confounding suitable for longitudinal studies that obtain data on exposure, covariate, and vital status at several points in time. An important difference between longitudinal studies and point exposure studies is that, in longitudinal studies, a time-dependent covariate can be simultaneously a confounder and an intermediate variable on the causal pathway from exposure to disease. In this paper I propose an estimator, the extended standardized risk difference, that provides control for confounding by a covariate that is simultaneously a confounder and an intermediate variable.

Data Interpretation, Statistical↗
PubMed1994

Intermediate variables as determinants of adverse pregnancy outcome in high-risk inner-city populations.

A probability sample survey of high-risk inner-city women with a live birth in the last 3 years shows that maternal medical risks and health behaviors during pregnancy are important intermediate variables influencing preterm delivery and birthweight. Women who developed two or more medical risks had about three-and-a-half times the risk of preterm delivery and two-and-a-half times the risk of low birthweight compared to those without such risks. Women with prior fetal loss had twofold increase in the risk of preterm delivery and low birthweight. Unintended pregnancy resulted in one-and-a-half to twofold increase in preterm delivery and low birthweight, respectively. Inadequate gestational weight increased the risk of preterm delivery by about 50%. Smoking during pregnancy raised the risk of low birthweight slightly more than one-and-a-half times.

Adolescent↗
PubMedDate not supplied

Reproductive change in Sri Lanka: analysis of intermediate variables, 1982 and 1987.

This study examines the intermediate determinants of fertility in Sri Lanka by making use of the data collected in the 1982 Sri Lanka Contraceptive Prevalence Survey and the 1987 Sri Lanka Demographic and Health Survey. The analysis shows that the most important inhibitor of potential fertility is deliberate control. The marital structure of the population is also an important fertility-inhibitor, but lactational infecundability is increasingly becoming an unimportant contributor. The findings show the success of the family planning program in Sri Lanka, which propelled fertility to a substantial lower level. Achievement of the replacement level fertility by the turn of the century, set by the Sri Lankan government, would largely depend on the efforts to increase the quality and quantity of contraceptive use and the duration of breastfeeding.

Adolescent↗
PubMed1980

Natural fertility and associated intermediate variables in some Arab countries.

"This paper will discuss the factors which affect natural fertility in the Middle East and North Africa based on data collected recently in selected countries of the region. First, however, it will consider conceptual approaches to the study of the intermediate fertility variables and problems in applying the concept of natural fertility to contemporary populations."

Africa↗
PubMedDate not supplied

Determinants of fertility decline in China, 1981: analysis of intermediate variables.

This study examines the proximate determinants of fertility in China by making use of the data collected by the One-per-Thousand Sample Fertility Survey of 1982. The results indicate that the most important inhibitor of potential fertility is deliberate control. Its contribution to fertility change has been far greater than all other proximate determinants. The marital structure of the population is also an important factor, while lactational infecundability and induced abortion are relatively unimportant. Comparative results by using data from the In-depth Fertility Survey conducted in Shanghai Municipality, Hebei and Shaanxi Provinces in April 1985 agree well in the ranking of the four intermediate factors. The findings point to successful family planning program and government population policies, which propelled the fertility transition to a substantial degree. Further research needs and policy implications of the results of the study are discussed.

Adolescent↗
PubMed1993

A study on socio-economic and intermediate variables on fertility.

"In this paper an attempt has been made to examine fertility differentials of currently married rural women [in Bangladesh] by their socioeconomic (viz, education of women, land ownership and family type) and demographic (viz, age at the first marriage, duration of breast feeding and duration of post partum amenorrhoea for the child) characterisation. This study is based on data collected from 995 currently married women of childbearing age. It has been found that women's (i) level of education (ii) age at first marriage (iii) duration of breastfeeding and (iv) duration of post-partum amenorrhoea, are inversely related with fertility. Joint family shows higher fertility than that of nuclear family and land ownership reveals [a] U-shaped relationship with fertility."

Amenorrhea↗
PubMed1982

Association of marital status and years of schooling with perinatal outcome: the influence of pre-natal care as an intermediate variable.

The association between mother's education and perinatal mortality, and between marital status and proportion of preterm deliveries was analyzed using data from 20,000 women and newborns delivered at the Hospital Barros Luco-Trudeau in Santiago, Chile. A highly significant correlation was found, but after being controlled by pre-natal care, that association disappeared for those mothers with good pre-natal care, remaining only as a part of the association for women who did not attend the pre-natal clinics or did not follow minimal standards of care. The definition used for "good pre-natal care" was much less demanding than WHO recommendation. We required a minimum of only 5 visits, starting before the 5th month of the pregnancy and with blood pressure and body weight registered at each visit. Pre-natal assistance was provided mostly by registered midwives, with occasional consultation by physicians. The efficiency of a low cost health activity, such as pre-natal care, in improving infant health is held in contrast with the inefficiency of high cost technology when applied to developing countries' health problems.

Chile↗