The findings are based on a community study of the older inhabitants of Dubbo, a town in NSW, Australia. Researchers found that there was an increase in mortality of all causes in later life in childless women while the more children women had, the more likely they were to live for longer.
The study examined the association of parity (the number of times a woman has given birth) with mortality in later life. 1233 men and 1571 women aged 60 or over entered the study in 1988-89. Each participant stated the number of children they had produced. The study population was broadly representative of the Australian population born before 1930 by gender, age, employment, socioeconomic status, housing tenure, tobacco use, mean blood pressure and other variables. All participants underwent standard demographic, psychosocial, physical disability, self-rated health and cardiovascular risk assessments when they entered the study. For the next 16 years, hospitalisation and death records were monitored continuously, with postal surveys conducted every two years to confirm vital status.
Researchers looked at links between parity and the following variables: age, cigarette smoking, any alcohol intake, body mass index (BMI), serum lipids and lipoproteins, diabetes, hypertension, peak expiratory flow, prior coronary heart disease or stroke, atrial fibrillation, depression score, physical activities of daily living and self-rated health.
The study showed that all-cause mortality rate declined with increasing parity. It was highest in nulliparous women (women with no children), progressively falling until women had 3 or more children. Women with six or more children had a risk of death of 40% lower than in nulliparous women.
The findings confirm results of studies in Norway and Israel, but contrast with a previous study conducted in England and Wales and published in 2005 which suggested that both nulliparous women and those with five or more children had increased mortality. The Dubbo study produced no statistically significant evidence linking male mortality with number of children fathered.
Professor Simons said: “There is increasing interest in associations between women’s childbearing history, parity in particular, and late-life mortality. The underlying mechanisms as to why the more children women have the longer they will live are unclear. Since high degrees of parity are now relatively uncommon in Western societies, the finding of reduced all-cause mortality and increasing parity is not of immediate practical application to public health. However, it would be interesting to investigate further the reasons behind the finding as there could be implications for improving maternal health.
“The conflicting findings of our study with the earlier study undertaken in England and Wales cannot be easily resolved. The differences may be related to study design or population socio-demographics.”
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Notes to Editors
1. Age and Ageing is an international journal publishing refereed original articles and commissioned reviews on geriatric medicine and gerontology. Its range includes research on ageing and clinical, epidemiological, and psychological aspects of later life. It is the official scientific journal of the British Geriatrics Society and is published by Oxford University Press.
2. The article, Childbearing history and late-life mortality: the Dubbo Study of Australian elderly, was written by Professor Leon Simons, University of New South Wales, Sydney, Australia, Judith Simons, University of New South Wales, Sydney, Australia, Yechiel Friedlander, Hebrew University-Hadassah, Jerusalem, Israel and John McCallum, National Health & Medical Research Council, Canberra, Australia and first published on 29 March 2012.
3. The Dubbo Study has received past support from the Australian National Health & Medical Research Council and National Heart Foundation, but the present analysis received no specific grant support.
4. The Dubbo Study has received approval from institutional ethics committees at St Vincent’s Hospital Sydney, the University of NSW and the University of Western Sydney and all subjects gave informed, written consent.
5. Fertility history and health in later life: a record linkage study in England and Wales was authored by E Grundy and C Tomassini and was published in Social Science and Medicine in 2005; 61:217-28.
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