Longevity - If the genes fit...

Ever wondered why females tend to outlive males? Is gender a ‘short-cut’ – a proxy to behavioural differences? Eli Friedwald takes a tour of the competing theories trying to explain the difference in life expectancy between the sexes

The European Court of Justice (ECJ) has recently ruled that the use of gender in determining prices for insurance contracts will not be permitted from 21 December 2012.

The clear thrust of the ruling is that insurance companies should be charging clients explicitly for adverse behaviours and not using gender as a ­convenient short-cut.

This prompts an obvious question: to what extent are the observed mortality differentials attributable to behavioural, rather than biological differences, between the genders?

The Advocate General at the ECJ presented its arguments for recommendation that gender-specific pricing be disallowed.

The arguments included that: “The Advocate General is of the opinion that the exception in question (the derogation) does not relate to any clear biological differences between insured persons (i.e. between the genders)”.

The opinion proceeds to describe other factors that may be responsible for observed gender mortality differentials, such as profession, social environment, eating habits, and consumption of stimulants and drugs.

But there are various theories put forward to explain differences in mortality between males and females.

Both genetic and hormonal explanations have been proposed to explain gender differences in mortality.

Genetic advantages for females

■ X and Y: every human has 23 pairs of chromosomes, containing strings of genetic material. One pair of these determines the gender.

Females carry two X chromosomes, one inherited from the mother and the other from the father.

Males carry one X chromosome inherited from the mother and one smaller Y chromosome inherited from the father.

The X chromosome contains genes which govern processes other than gender determination.

It is thought that the second X chromosome gives females a ‘back-up’ for any abnormal genetic information inherited from one parent – males have only one chance to get it right

■ Ras-GRF1: this gene, which is active only in males, has been identified as having a detrimental impact on longevity

■ Telomeres: these are the ‘book ends’ of chromosomes that protect the genes when a cell divides.

At each cell division, the telomeres shorten. When these reach a critical length, the cells can no longer divide, so that tissue damage cannot be repaired and eventually leads to organ failure.

Research has indicated that telomeric shortening occurs less rapidly for females than for males. This concludes that this is why females age more slowly than males.

Hormonal advantages for females

Oestrogen, the female hormone, appears to be protective against cardiovascular risks, which represent a major cause of death among males.