Increase in life expectancy at birth was accompanied by the emergence of a gap in favour of women which progressively
widened to about 6-7 years: the longevity gender gap. On the other hand, excess of disability is currently observed to the
detriment of women, cancelling their longevity advantage: the disability gap. Many researchers simply conclude that
women live longer but in poorer health than men [42, 43]. The female survival advantage can be tracked back to conception
with a very large ratio of male per female conception leading to the actual ratio of 105 males for 100 females at birth [44].
A small longevity gap, between 1 and 3 years, in favour of women has been observed in pre-transitional societies in line
with studies suggesting the existence of a small female survival advantage in many species possibly due to similar genetic
and hormonal processes impacting on cholesterol levels and immune functions and possibly also related to parenting
and child rearing. In fact, the widening of the human gender gap is a very recent phenomenon, probably due to 20th
century social and economic transformation, benefiting apparently women more than men. The widening of the gap
corresponds to a transitional period between conditions when the greatest danger to life was starvation and infectious
diseases to modern conditions when the greatest danger is opulence and high caloric intake leading to metabolic imbalance.
The question then is why women can derive a greater or a faster benefit from these changes in living conditions.
Another question is what will be the residual gap when men will possibly have caught up with the transition [4547].
A number of biological and social factors have been put forward to explain gender-specific behaviours, habits and beliefs
which can lead to the observed longevity gaps. Most researchers focus only on the longevity gap and favour a simple biological
or social theory such as the chromosomal, hormonal, oxidative and replicative theories on the biological side, and stress-related
job and gender roles, smoking and risk behaviour, social constructionist and feminist theories on the social science side
[45, 4850]. Only a few look for a coherent explanation working both for the longevity and the disability gaps.
Indeed, everything that distinguishes men and women can contribute to explain the longevity and disability gap [42].
A number of these conditions have changed over time and can contribute to explain the widening of the gaps. On the other hand,
women have a lower level of functioning. Studies consistently show that a greater percentage of women are disabled compared to
men. Although it is not clear whether there are gender differences in the reporting of disability, the prevalence of total
disability in older women can be estimated to be approximately 50 percent higher than in men. At every level of co-morbidity
women have greater disability [47]. Women have been presented as the sicker gender. The use of behavioural indices
(bed rest, sick leave, number of contacts, health care utilisation, self reported morbidity) will confound our understanding
of morbidity because they actually represent how men and women cope with illness rather that representing their true
health status. Depression provides a good example. Despite the fact suicide rates are much higher for men than for women,
depression is thought of as a female problem because women are seeking more help for depression. Instead,
men tend to engage in private activities, including drinking and drug abuse, designed to alleviate their depression [47, 50].
Several hypotheses have been raised on the biological side to explain the gender gaps [46, 5156].
But none of the basic biological factors has significantly changed through the 20th century and cannot contribute to explain
the widening of the gaps [45]. According to Stindl, the longevity gap could be explained by the difference in body size between
men and women, needing a different number of replications and then leading to a different length of telomeres. Change in body
size through the 20th century would explain the widening of the gaps, men being closer to their replicative limits [57].
Women may also be better able to cope with overnutrition than men. Indeed, female advantage for survival may arise in
prosperous countries by innate ability of the female body to mobilise and transport nutrients for the benefit of the foetus
in pregnancy, giving them a better excretory system. In this case caloric restriction may be more efficient for males [58].
On the social science side, smoking has been the main explanation for many years. According to the tobacco theory,
the longevity gap should continue reducing as women approach the same total smoking years as men [45]. While men
and women engage in different social practices to demonstrate their masculinities and femininities respectively, male beliefs
and behaviours undermine their health whereas female beliefs and practices reinforce their longevity. In traditional
Western societies, men should be independent, strong and tough, taking risks (from street violence to skydiving,
according to social class), refusing to acknowledge physical discomfort and need of help, and refusing positive health
behaviour such as using sunscreen. Moreover, health care utilization and positive health beliefs or behaviors can be
viewed as a form of idealized femininity [50].
Box 1: A sampling of hypotheses regarding the gender gap in health and longevity.