ReviewFrailty in older women
Introduction
The world's population is ageing. During the 19th and early 20th centuries, improvements in living conditions reduced infant mortality, resulting in greater numbers of people surviving to middle and old age; more recent medical advances have allowed older people themselves to live longer. Indeed, over the last 170 years average life expectancy has increased by three months per year in developed countries [1]. These increases have not been gained equally by men and women. In the UK, significant differences in life expectancy persist from birth (78.7 years for men and 83.6 years for women) throughout youth and middle age, becoming proportionally greatest for the oldest old (5.0 years and 6.4 years for 85 year old men and women, respectively) [2].
Although women live longer than men, they tend to have poorer health status. This well described phenomenon has been termed the male–female health-survival paradox [3]. In mid and old age, women have greater levels of disability, more psychological and physical co-morbidity and worse self-rated health. These deficits in multi-dimensional health domains can be measured by a “Frailty Index” [4]. A Frailty Index is a count of health deficits, expressed as a proportion. For example, if 50 health deficits were used to make up a Frailty Index, a person with no health deficits would have a Frailty Index of 0; someone with 20 deficits would have a Frailty Index of 0.4, and, in theory, were an individual to have all 50 health deficits – as we shall see, and intriguingly, this never happens – the maximum score of the Frailty Index would be 1.0. Frailty Indices can be calculated from most existing clinical and population health surveys, making them a feasible means of quantifying health status. Their validity is indicated by their high correlation with adverse outcomes, including institutionalisation, worsening disability and death [5]. Investigations of Frailty Indices in large population studies have consistently shown that at any given age older women have accumulated more deficits than do men, but have lower mortality [5], [6]. This is of some interest. While in both men and women, increasing values of the Frailty Index, representing accumulation of a greater number of health deficits, are associated with worse mortality, it seems clear that the vulnerability to adverse outcomes cannot be mapped directly to the number of deficits. In other words, if we understand frailty as the variable vulnerability to adverse outcomes of people of the same chronological age, there must be some mediating factors between health deficits and susceptibility. Sex could be one such factor.
Here, we briefly review the biological, social and behavioural factors that may explain women's greater longevity. We consider the factors contributing to frailty status, evaluating why older women have a greater deficit burden. The measurement of frailty by a Frailty Index is consistent with the conceptualisation of ageing as the failure of a complex system: we explore how this may afford a mechanistic understanding of the male–female health-survival paradox.
Section snippets
Why do women live longer than men?
In most countries throughout the developed and developing world, women tend to have longer life expectancy at birth and lower age-specific mortality rates [7]. There are a few exceptions: women in some South Asian countries have shorter life expectancy, thought to be secondary to preferential treatment of male children and complications associated with pregnancy and childbirth [8].
Historical evidence suggests that longer lifespans of women are not a recent phenomenon. Although some believe that
Are women more frail than men?
Just as it has been known for several centuries that women live longer lives than men, their poorer health status has also long been recognised. Physicians in 17th-century London, for example, reported that in addition to unique complications associated with pregnancy and childbirth, women generally suffered more than men from diseases [17].
The higher rates in lifetime prevalence of different diseases in women were previously attributed to the impact of their longer life expectancy on
Why is frailty important?
Frailty, as variable vulnerability to adverse outcomes, is an important concept for all those who plan and provide care for older people. It is closely linked to advanced age and disease-related processes, yet is a distinct construct. Frailty allows health status to be summarized in a parsimonious way, providing a more precise quantification of individual vulnerability than chronological age alone; those who are frail are at increased risk of death, institutionalisation and worsening disability
Why do women with health deficits live longer?
In this review, we have established that women have longer life expectancies and a greater frailty burden; the underlying reasons for these two disparate phenomena have been explored. We must now address the question of why women can tolerate this greater number of heath deficits. In one study, for example, women had an estimated 20% lesser chance of dying at a given time than did men of the same chronological age and degree of frailty [6]. The conceptualisation of ageing as the failure of a
Conclusions
In old age, women tend to have more deficits than do men, and be frailer by current definitions, but live longer lives. While many explanations have been proposed to account for these phenomena separately, there is much that still needs to be done to understand frailty and why it impacts older men and women in different ways. Complex interventions, particularly education and exercise, may modify the rate of deficit accumulation and delay the onset of frailty. Whether such interventions will
Contributors
REH wrote the first draft which was revised by KR.
Competing interests
KR has applied for funding to commercialize a version of the Frailty Index.
Funding
KR receives career support from the Dalhousie Medical Research Foundation as Kathryn Allen Weldon Professor of Alzheimer Research. Much of the work done here was supported by the Canadian Institutes of Health Research through operating grant MOP005170.
Provenance and peer review
Commissioned and externally peer reviewed.
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