Women outlive men on average in every country where reliable records exist. The size of the gap varies considerably, and that variation is what makes the causes traceable.
The gap is universal but not fixed
A consistent difference across societies with very different economies, diets and healthcare systems points to a biological component.
The width of the gap nevertheless differs substantially between countries and has changed over time within the same country.
A universal floor with large variation on top is the signature of biology plus behaviour, and both parts have been studied.
Sex hormones affect cardiovascular risk differently
Cardiovascular disease tends to develop later in women, with the difference narrowing after menopause.
Oestrogen influences circulating lipids and the behaviour of blood vessel walls, and its decline is followed by a rise in risk.
Male mortality is weighted earlier in life for this reason, and cardiovascular disease is the single largest contributor to the overall gap.
Two chromosomes provide a spare copy
Females carry two X chromosomes and males one, so a damaging variant on the X has no counterpart to compensate in males.
This explains why several conditions linked to that chromosome occur predominantly in men.
Immune function also differs, with women mounting stronger responses to infection, a pattern that carries its own trade-off in higher rates of autoimmune conditions.
Behaviour accounts for much of the variation
Smoking and heavy drinking have historically been more common among men, and the difference in smoking prevalence tracks the size of the mortality gap over time closely.
Deaths from accidents, violence and suicide are higher among men in most countries, and these are concentrated in younger age groups where each death removes many years.
Occupational exposure to physical hazards has also been unevenly distributed, though that distribution has shifted.
Help-seeking patterns compound the rest
Men present later with symptoms on average and attend routine appointments less often, which shifts diagnoses towards more advanced stages.
Late presentation limits which treatments remain available, and the effect is largest for conditions where early detection changes the outcome.
Symptoms are also reported differently. Descriptions offered to a clinician tend to be briefer and to omit context, which affects what gets investigated.
This part of the gap is the most modifiable, which is why screening participation and prompt assessment of symptoms are emphasised in men's health specifically. The biological component sets a floor; the rest of the difference has moved before and can move again.