Small for Gestational Age and Age at Puberty: Evidence From Hong Kong's "Children of 1997" Birth Cohort

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

Related collections

Most cited references 45

Record: found
Abstract: found
Article: not found

Using the outcome for imputation of missing predictor values was preferred.

Karel Moons, Rogier A. R. T. Donders, Theo Stijnen … (2006)

Epidemiologic studies commonly estimate associations between predictors (risk factors) and outcome. Most software automatically exclude subjects with missing values. This commonly causes bias because missing values seldom occur completely at random (MCAR) but rather selectively based on other (observed) variables, missing at random (MAR). Multiple imputation (MI) of missing predictor values using all observed information including outcome is advocated to deal with selective missing values. This seems a self-fulfilling prophecy. We tested this hypothesis using data from a study on diagnosis of pulmonary embolism. We selected five predictors of pulmonary embolism without missing values. Their regression coefficients and standard errors (SEs) estimated from the original sample were considered as "true" values. We assigned missing values to these predictors--both MCAR and MAR--and repeated this 1,000 times using simulations. Per simulation we multiple imputed the missing values without and with the outcome, and compared the regression coefficients and SEs to the truth. Regression coefficients based on MI including outcome were close to the truth. MI without outcome yielded very biased--underestimated--coefficients. SEs and coverage of the 90% confidence intervals were not different between MI with and without outcome. Results were the same for MCAR and MAR. For all types of missing values, imputation of missing predictor values using the outcome is preferred over imputation without outcome and is no self-fulfilling prophecy.

0 comments Cited 326 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

On the pitfalls of adjusting for gestational age at birth.

Clarice R. Weinberg, Olga Basso, Allen Wilcox (2011)

Preterm delivery is a powerful predictor of newborn morbidity and mortality. Such problems are due to not only immaturity but also the pathologic factors (such as infection) that cause early delivery. The understanding of these underlying pathologic factors is incomplete at best. To the extent that unmeasured pathologies triggering preterm delivery also directly harm the fetus, they will confound the association of early delivery with neonatal outcomes. This, in turn, complicates studies of newborn outcomes more generally. When investigators analyze the association of risk factors with neonatal outcomes, adjustment for gestational age as a mediating variable will lead to bias. In the language of directed acyclic graphs, gestational age is a collider. The theoretical basis for colliders has been well described, and gestational age has recently been acknowledged as a possible collider. However, the impact of this problem, as well as its implications for perinatal research, has not been fully appreciated. The authors discuss the evidence for confounding and present simulations to explore how much bias is produced by adjustments for gestational age when estimating direct effects. Under plausible conditions, frank reversal of exposure-outcome associations can occur. When the purpose is causal inference, there are few settings in which adjustment for gestational age can be justified.

0 comments Cited 118 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Menstrual cycles: fatness as a determinant of minimum weight for height necessary for their maintenance or onset.

Todd J. McArthur, R E Frisch (1974)

Weight loss causes loss of menstrual function (amenorrhea) and weight gain restores menstrual cycles. A minimal weight for height necessary for the onset of or the restoration of menstrual cycles in cases of primary or secondary amenorrhea due to undernutrition is indicated by an index of fatness of normal girls at menarche and at age 18 years, respectively. Amenorrheic patients of ages 16 years and over resume menstrual cycles after weight gain at a heavier weight for a particular height than is found at menarche. Girls become relatively and absolutely fatter from menarche to age 18 years. The data suggest that a minimum level of stored, easily mobilized energy is necessary for ovulation and menstrual cycles in the human female.

0 comments Cited 100 times – based on 0 reviews      Review now

Bookmark

All references

Author and article information

Journal

Title: American Journal of Epidemiology

Abbreviated Title: American Journal of Epidemiology

Publisher: Oxford University Press (OUP)

ISSN (Print): 0002-9262

ISSN (Electronic): 1476-6256

Publication date Created: October 26 2012

Publication date (Print): October 16 2012

Volume: 176

Issue: 9

Pages: 785-793

Article

DOI: 10.1093/aje/kws159

SO-VID: 4f597021-fafb-4654-9ed8-8ec3558f4d9d

History

Data availability:

Comments

Comment on this article

scite_

Cited by 7

See all cited by

Most referenced authors 501

See all reference authors

Small for Gestational Age and Age at Puberty: Evidence From Hong Kong's "Children of 1997" Birth Cohort

Read this article at

Abstract

Related collections

Biomarkers for Inflammatory Lung Disease

Most cited references 45

Using the outcome for imputation of missing predictor values was preferred.

On the pitfalls of adjusting for gestational age at birth.

Menstrual cycles: fatness as a determinant of minimum weight for height necessary for their maintenance or onset.

Author and article information

Journal

Article

History

Comments

Comment on this article

Similar content 777

Cited by 7

Most referenced authors 501