Volume 60, Part 1, 2006 - March 2006

Authors: M. Giovanna Merli, Sara Hertog, Bo Wang, and Jing Li
Title: Modelling the spread of HIV/AIDS in China: The role of sexual transmission

The study presented here is an exploration of the implications of patterns of sexual behaviour for the spread of HIV in China, using a bio-behavioural macrosimulation model.

To reflect the uncertainty surrounding key parameters, analyses of varied scenarios are used to show a range of possible outcomes consistent with variations in selected biological and behavioural inputs. The latter are estimated from a nationwide survey of sexual behaviour recently conducted in China, a country with an emerging HIV/AIDS epidemic, where it is feared that HIV/AIDS will spread to the general population via heterosexual transmission. The results highlight the primacy of the levels and distribution of sexual activity in the population.

They offer some guidelines for understanding and interpreting the potential implications of current and prospective changes in sexual behaviour for the spread of HIV/AIDS in the world's largest population, and also highlight the need to collect better data on sexual behaviour for the estimation of key model inputs.

Keywords: HIV; AIDS; modelling; sexual behaviour; China
pp. 1-22

Authors: Jona Schellekens and Frans van Poppel
Title: Religious differentials in marital fertility in The Hague (Netherlands) 1860-1909

Previous studies of the marital fertility transition in Europe have found religious differentials. Using data collected from the population registers of The Hague, our aim in this study is to search for answers to the following questions: whether religious differentials result from socio-economic characteristics; to what extent religious ideology explains the behaviour of religious groups; which proximate determinants account for the religious differentials; and whether the Jews were forerunners in the marital fertility transition in Europe.

The results provide some evidence of relatively low levels of parity-dependent fertility control among Jews before the transition and among Catholics during the transition. Religious ideology probably accounts for the low level of fertility control among Catholics. The ultimate reason for the relatively high marital fertility among Jews before the transition remains unclear. Our findings do not support the hypothesis that Jews were forerunners in the marital fertility transition.

Keywords: marital fertility; religious differentials; minority-group status; parity-dependent fertility control; population registers; discrete-time repeated events history model.
pp. 23-38

Authors: Robert F. Schoeni, Jersey Liang, Joan Bennett, Hidehiro Sugisawa, Taro Fukaya, Erika Kobayashi
Title: Trends in old-age functioning and disability in Japan, 1993-2002

Disability is a burden to individuals and society. Population ageing, combined with the fact that disability is most common among the elderly, has focused attention on trends in old-age disability.

This study estimates trends in functioning and disability among Japanese elderly from 1993 to 2002 and contrasts the patterns with those found in the US. Japan is an especially interesting country because its age structure is relatively old, and it currently has the highest life expectancy in the world despite the fact that just 50 years ago its life expectancy was in the bottom half of all countries. Like the US, disability rates have fallen.

If it were not for the gains in disability between 1993 and 2002, there would have been 1.1 million more disabled elderly in 2002. The reductions were experienced broadly across socio-demographic and economic groups. Increases in education across cohorts are associated with the declines in disability.

Keywords: disability; trends; elderly; Japan
pp. 39-53

Authors: L.S. Hurt, C. Ronsmans, S. L. Thomas
Title: The effect of number of births on women's mortality: Systematic review of the evidence for women who have completed their childbearing

Mortality in women who have completed their childbearing may increase with the number of births experienced because of maternal depletion or a trade-off between reproduction and mortality. We report a systematic review of the evidence on this association. We searched Medline, Embase, Popline, and the Science Citation Index for published and unpublished studies up to September 2003, and the book catalogues of relevant London libraries.

Where necessary we also contacted authors for additional information. Mortality declined with increasing numbers of births in twelve historical cohorts but, in eight contemporary cohorts, the highest mortality was seen in the nulliparous and in women with more than four births. All effects seen were small and there were few statistically significant results.

Studies examining the relationship in other ways (such as by linear trends or by mean number of births by age at death) found inconsistent associations. We discuss methodological, social, and biological factors that may have affected these associations.

Keywords: reproductive history; childbearing; parity; women; survival; mortality
pp. 55-71

Author: Alessandro Rosina
Title: A model with long-term survivors for the analysis of current-status nuptiality data

The model proposed in this paper combines a logistic regression model and a Weibull regression model for the analysis of current-status data. This joint model allows a simultaneous estimation of two sets of effects on the covariates: one on the probability that the event occurs (also known as quantum) and the other on the timing of the event.

Thus, the model can be seen either as an extension of a survival-analysis model for use with current-status data where a survival fraction is added in order explicitly to take into account the possibility that the event may never occur, or as an extension of survival analysis with long-term survivors to the analysis of current-status data. As an illustrative application we apply our model to a study of nuptiality in seventeenth-century Italy. .

Keywords: survival analysis; event-history analysis; current-status data; long-term survivors; mixture models
pp. 73-81

Authors: Barthélémy Kuate-Defo and Julie DaVanzo
Title: Reliability of reasons for early termination of breastfeeding: Application of a bivariate probability model with sample selection to data from surveys in Malaysia in 1976-77 and 1988-89

Although extensively collected, data on people's reasons for their behaviour provided retrospectively have been met with some scepticism on the grounds that they may be subject to biases and errors that jeopardize their usefulness. This study investigates, for a sample of 1,327 births, the reliability with which women in Peninsular Malaysia recalled, at intervals 12 years apart, reasons for not initiating or for stopping breastfeeding less than three months after a birth. Overall, we find low to moderate reliability of recall.

Levels of reliability are relatively high for some reasons (the child died and no or insufficient milk) but low for some others (child ill, breastfeeding inconvenient). Results from selection models show that reliability does not vary with the length of time since the child's birth but is inversely related to socioeconomic status (proxied by education and employment). Social status, social norms, and health-related factors appear to be significant influences on women's consistency of reporting.

Keywords. Breastfeeding, data quality, reasons, reliability, reproducibility, Malaysia, attrition bias, bivariate probit selection models, sample selection bias, selection model.
pp. 83-98

Authors: Jean-Marie Robine, Graziella Caselli, Domenica Rasulo, and Amandine Cournil
Title: Differentials in the femininity ratio among centenarians: Variations between northern and southern Italy from 1870

Significant differentials have been observed between Italian regions in the distribution of centenarians by sex, from two women per man in the south to over eight in certain regions in the north. In order to explain these differentials we studied the evolution of the femininity ratio (FR), using a longitudinal approach to follow the ageing process in two cohorts, and making use of nearly all the statistical data available since the time of the Unification of Italy in 1870.

Significant differentials in the FR observed at the age of 100 are mainly due to mortality differentials among men over the age of 60. The high mortality of men in the north and their low mortality in the south are the main explanations of why the FRs are higher in the north and lower in the south. Mortality differentials among women have only a marginal impact.

Keywords: centenarians; sex ratio; femininity ratios; age pattern; cohort study; Italy; mortality; regional differences
pp. 99-113