Elsevier

Social Science & Medicine

Volume 67, Issue 9, November 2008, Pages 1456-1464
Social Science & Medicine

Marital and cohabitation status as predictors of mortality: A 10-year follow-up of an Italian elderly cohort

https://doi.org/10.1016/j.socscimed.2008.06.026Get rights and content

Abstract

The relationship between mortality and marital status has long been recognized, but only a small number of investigations consider also the association with cohabitation status. Moreover, age and gender differences have not been sufficiently clarified. In addition, little is known on this matter about the Italian elderly population. The aim of this study is to examine differentials in survival with respect to marital status and cohabitation status in order to evaluate their possible predictive value on mortality of an Italian elderly cohort. This paper employs data from the Italian Longitudinal Study on Aging (ILSA), an extensive epidemiologic project on subjects aged 65–84 years. Of the 5376 individuals followed-up from 1992 to 2002, 1977 died, and 1492 were lost during follow-up period. The baseline interview was administered to 84% of the 5376 individuals and 65% of them underwent biological and instrumental examination. Relative risks of mortality for marital (married vs. non-married) and cohabitation (not living alone vs. living alone) categories are estimated through hazard ratios (HR), obtained by means of the Cox proportional hazards regression model, adjusting for age and several other potentially confounding variables. Non-married men (HR = 1.25; 95% CI: 1.03–1.52) and those living alone (HR = 1.42; 95% CI: 1.05–1.92) show a statistically significant increased mortality risk compared to their married or cohabiting counterparts. After age-adjustment, women's survival is influenced neither by marital status nor by cohabitation status. None of the other covariates significantly alters the observed differences in mortality, in either gender. Neither marital nor cohabitation status are independent predictors of mortality among Italian women 65+, while among men living alone is a predictor of mortality even stronger than not being married. These results suggest that Italian men benefit more than women from the protective effect of living with someone.

Introduction

The influence of marriage on health and survival has been repeatedly investigated in a large number of studies reporting an overall greater longevity and better health status of married as compared to unmarried individuals (Goldman et al., 1995, Ikeda et al., 2007, Johnson et al., 2000, Manzoli et al., 2007, Martikainen et al., 2005, Valkonen et al., 2004).

Explanations for differences in mortality by marital status have been usually divided into two broad categories, which refer to a selection and a protection link between marriage and health. According to the first mechanism, physically and psychologically healthier individuals are more likely to be selected for marriage and remarriage, with a consequent concentration of health problems among the non-married groups. On the other hand, marriage should have a protective effect on health status through the provision of social and economic support. As a consequence, better health behaviours and a healthier life style may be in turn the result of both selection and protection mechanism of marriage. In addition, the excess mortality among non-married subjects could be attributable to the stress of bereavement or of marital dissolution experienced by widowed or divorced/separated individuals (Bowling and Charlton, 1987, Martikainen and Valkonen, 1996, Nagata et al., 2003, Williams and Umberson, 2004).

Only a small number of investigations on this specific subject examine the association with cohabitation status, living arrangements or social networks, and in general they show a protective effect of larger networks on mortality of elderly individuals (Giles et al., 2005, Lund et al., 2002, Rodriguez-Laso et al., 2007). Lund et al. (2002) also find that cohabitation status is a more relevant indicator of social support than marital status, and suggest replacing marital status with cohabitation status in future studies on social networks and mortality, since it may account for more of the variation in mortality. This result appears particularly relevant because living with a partner, without formal marriage, or with a friend, has become relatively common in developed countries, including Italy, and the share of single, divorced and widowed persons who actually cohabit with someone else (partner, friend, relative, caretaker, etc.) is increasing even among older subjects (ISTAT, 2006).

As regards age and gender differences in the association between marital and cohabitation status and health, the results of previous studies are rather conflicting and the real magnitude of the phenomenon has not been sufficiently clarified. In general, men are reported to benefit from the advantages of marriage more than women (Goldman et al., 1995, Ikeda et al., 2007, Munch and Svarer, 2005, Williams and Umberson, 2004) and the positive influence of marital status on health seems to be weaker among elderly subjects than among younger individuals (Ikeda et al., 2007, Johnson et al., 2000, Manor et al., 2000, Manor et al., 1999, Williams and Umberson, 2004). On the other hand, some studies find no significant gender differences in relation to marital status (Johnson et al., 2000, Manor et al., 2000, Manzoli et al., 2007), while Lund et al. (2002) find neither gender nor age differences in the association between living arrangements and mortality. Moreover, Valkonen et al. (2004), in a demographic study carried out on mortality from 1970 to mid 1990s in 10 western developed countries (not including Italy), show that for subjects aged 65–74 years there has been a trend towards increasing mortality disadvantage among non-married persons; but this trend, which is evident only among single elderly men, is more systematic among women of all non-married sub-groups.

Thus, the links between marital status and health are not definitely understood, with findings varying by community, gender, age and sub-types of non-married individuals investigated. It is not clear if this may be due to the real effect of cohabitation and marital status, to socio-cultural differences between countries, to differences in the study design and selection of variables or also to the different analytical strategies adopted.

In addition, little is known on this matter about Southern European countries and the Italian elderly population in particular. Apart from an extensive study on mortality differentials among Israeli men (Manor et al., 1999) and women (Manor et al., 2000) aged over 45, and a recent study on the effect of social relationships on survival of a Spanish elderly sample (Rodriguez-Laso et al., 2007), almost all the investigations present in scientific literature are concentrated on populations from Northern European countries, United States, Canada, Australia, Japan. Rodriguez-Laso et al. (2007) report that having contact with all family ties is associated with a reduced mortality only among men, while the beneficial association between survival and other social relationships (having a confidant, participate in social activities, being engaged in meaningful roles, etc.) is essentially comparable for men and women. Only one, out of the 40 studies examined in a recent meta-analysis on marital status and mortality in the elderly (Manzoli et al., 2007), is conducted also by Italian researchers (Noale et al., 2005). They undertake an international comparison on predictors of mortality in six longitudinal studies on aging, including results from the Italian Longitudinal Study on Aging (ILSA) and the Spanish Longitudinal Study on Aging in Leganés after 5 years of follow-up. According to this international comparison, marital status did not show a homogeneous effect on mortality in the six countries examined: being married seems to be a protective factor in Finland, Israel, Italy, Spain but it behaves as a risk factor in Sweden, while no association is detected in the Netherlands.

On the basis of such considerations, we focus on two central issues:

  • (a)

    the association between marital and cohabitation status and mortality in a 10-year follow-up study on elderly Italian subjects;

  • (b)

    the role of other socio-demographic, biological and health factors in mediating the relationship between marital and cohabitation status and mortality in elderly subjects.

In the analysis presented below we explore these issues in the ILSA unified data set, derived from a longitudinal, multicentre, population-based study on a quite large sample of elderly persons followed-up over a period of 10 years. The ILSA contains comprehensive information on both explanatory and outcome variables, such as health history, life habits, disability, biological characteristics, depression, cognitive status, and mortality, that may be essential to assess whether and to what degree marital and cohabitation status influence survival in elderly Italian subjects.

Section snippets

Study population

The present work is part of the Italian Longitudinal Study on Aging (ILSA) that has been described in detail elsewhere (Maggi et al., 1994, The Italian Longitudinal Study on Aging Working Group, 1997). The ILSA main objectives are to investigate frequency, risk and protective factors of major age-associated conditions, and to study physical and functional changes among an Italian elderly cohort. A random sample of 5632 subjects aged 65–84 years, both community dwelling and institutionalized,

Results

A total of 4514 subjects (2199 women and 2315 men) out of the original study population answered the question on marital status. Among women 10.0% were unmarried, 37.7% married, 1.0% separated or divorced, 50.8% widows, and 0.5% clergywomen. The corresponding figures for men were 4.6%, 78.8%, 1.1%, 15.0% and 0.5%. After classification into the two main groups of married and non-married, 37.7% of women resulted married and 62.3% non-married, 78.8% of men were married and 21.2% non-married.

The

Discussion

The results of the 10-year survival follow-up of a sample of Italian elderly suggest that living alone, even more than being non-married, is a strong predictor of mortality for men, while, after age-adjustment, women's survival seems to be influenced neither by marital nor by cohabitation status. Adjustment for several potential confounding variables (biological measures, life habits, education, procreation, disabilities in activities of daily living, depression, and cognitive impairment) does

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    As part of the Progetto Finalizzato Invecchiamento, the ILSA was supported by the Italian National Research Council, with annual grants to each research unit from 1991 to 1995. The study was then supported by two grants from the Italian Ministry of Health (D.L. 502/92, 1998): “Epidemiologia dell'anziano” and “Previsione del fabbisogno sanitario dell'anziano”. The authors wish to thank Sonia Martire for her administrative support and assistance in preparing the manuscript.

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