It is the time of life that a woman should be able to feel her most confident.
Once she reaches her 50s, she has experienced the ups and downs of relationships, taken responsibility at work or home and seen a little - or even a lot - of the world.
Yet it seems that many women of this age don't feel confident at all, especially when it comes to the opposite sex.
In fact, by the time they reach 51, many women believe they have become invisible to men.
The days of admiring glances and appreciative smiles ebb away and they are left feeling unnoticed and even ignored.
This worrying portrait of an invisible middle age - starting at 51 - emerged in a study of 2,000 women.
More than two thirds of those over 45 told how they had walked into a room and been "completely unnoticed" by the opposite sex.
More than half said they felt "left on the shelf" and judged negatively simply because of their age.
Only 15 per cent of those over 45 declared themselves as having high or very high confidence while nearly half described themselves as not very confident at all.
But why, with all their achievements and experience, were these women so lacking in self-belief?
Four in ten said missing out on male attention was a factor while for more than half, the presence of younger women at a social event was totally confidence sapping.
Many blamed greying hair, having to wear glasses or even struggling to find fashionable clothes.
Six in ten felt modern life was geared towards younger women while 46 per cent believed that the problems faced by older women - such as the menopause, weren't spoken about.
The research, commissioned by herbal remedies company, A.Vogel, also examined the effect the menopause has on women's confidence as they age.
Health expert Eileen Durward, who offers advice through the company's website, was sympathetic to the older woman's plight. "The world can feel very geared toward appreciating younger women, leaving those of a certain age to feel neglected or less worthy. These women are not invisible and neither are their concerns," she said.
"They are often the driving engine behind a family, juggling careers, looking after older relatives and bringing up children, all the while dealing with the ageing process. They need to be supported, not made to feel washed up."
Actress Kristin Scott Thomas, 53, has spoken frankly about her fears that she will "just disappear" into middle age.
Last year she told how she felt like an "old ragbag" compared to younger co-stars and confided that she felt "invisible" while surrounded by young actresses at the Cannes Film Festival.
"I'm not talking about in a private setting, at a dinner party or anything. But when you're walking down the street, you get bumped into, people slam doors in your face - they just don't notice you," she said.
"Somehow, you just vanish. It's a cliché, but men grow in gravitas as they get older, while women just disappear."