The claim that it's a man's world may soon be put to test. A leading scientist sounds a warning today that social, sexual and health trends are driving the male of the species towards extinction.

As their gender weakens, men could become socially and biologically redundant leaving women in the ascendancy, according to Professor Siegfried Meryn, chairman and president of the First World Congress on Men's Health opening in Vienna this week.

To head off this impending disaster – for men – the congress will mark Men's World Day tomorrow with the launch of a series of research initiatives to investigate why male supremacy is in decline.

Writing in the British Medical Journal, Professor Meryn of the Institute of Medical Education at the University of Vienna, and Alejandro Jadad of the University of Toronto, Canada, say one of the great medical mysteries is why women live on average seven years longer than men when most of the social determinants of health are in men's favour.

Women face the exigencies of bearing and raising children, carry most of the burden of running the home, have poorer jobs and pay and gain less from marriage than men. Yet men have higher death rates from all 15 leading causes of death, including heart disease, cancer, suicide, accidents and Aids, and are twice as likely to die before they are 65.

Despite men's physical fragility, their social dominance has gone unchallenged for decades, but that too is now under threat. The authors say that as women improve their social position they are likely to extend their physical advantage.

"Although there is still a long way to go in most societies around the world, it is clear that women can perform (and on most occasions outperform) pretty much all the tasks reserved for men," they write. "In most of the developed world women are ... making rapid gains in terms of equality in compensation and opportunities in the workforce. Will we see the gaps in life expectancy widen as the gaps in social determinants of health become narrower? The answer is probably yes."

Advances in reproductive health – sperm banks, in vitro fertilisation, independent fertilisation of eggs with somatic cells – threaten redundancy for men as sexual partners while changes in social roles raise questions about their place in the home and the family. "Will men be needed at all?" the authors ask.

A sharp rise in psycho-social disorders, including alcohol and drug abuse, depression, domestic and other forms of violence add to the catalogue of men's ills. The authors point out that more than 30 wars and conflicts are raging around the world "mostly created, maintained and aggravated by men".

Separate figures published yesterday by the Department of Health show men compulsorily detained in mental hospitals now outnumber women, having risen 76 per cent in a decade. There were 7,100 men and 8,600 women sectioned under the Mental Health Act in 1990-91. By 2000-01 the balance had shifted with 12,500 men and 11,500 women.

Ian Banks, president of the European Men's Health Forum, writes in the journal that one cause of men's poorer health is their reluctance to consult a doctor. Deaths from melanoma, the severe form of skin cancer, are 50 per cent higher in men but the disease is 50 per cent commoner in women.

"Health and the lack of it is perceived by many men ... to be the domain of women."