If you want to know how a woman will age, you are advised to look at her mother.
But the secret to looking a decade younger is not just in the genes, it has emerged, as a third of women who appear younger may simply have lived more sensibly.
A study has found getting eight hours or more of sleep a night, taking a multi-vitamin and doing regular exercise all make women more likely to look younger.
But less organised women, who forget to moisturise, sometimes leave off the sunscreen and do not manage to stay at their target weight all damage their chances of ageing well.
Research by Harvard University, with the skincare company Olay, previously found some women aged 20 to 74 were frequently told they looked more than 10 years younger, and that these women had genes which expressed themselves differently.
A follow-up study by the firm found however that only two-thirds of these women carry the two main genetic variations now found to affect skin.
Looking at the third without good genes, they found sensibly sleeping enough made someone 10 per cent more likely to appear younger. Taking multi-vitamins increased their chances by 18 per cent and regular exercise by 14 per cent.
Unsurprisingly, smoking and sunshine remain bad for your skin, the research with genetics company 23andMe found.
Of more than 155,000 women surveyed, those who reported sunbathing frequently in had around a third lower likelihood of looking a decade younger.
Despite the pollution, it means women in cities are better off than those in the countryside, who tend to spend more time outside exposed to damaging ultraviolet light.
But the results show that, despite the old adage that ageing women can save their body or their face, that being thin is not bad for your skin.
Women who are overweight, with a BMI above 25, were found to cut their chances of looking young by a fifth. The researchers said it may be that putting on weight affects overall health.
Dr Frauke Neuser, principal scientist for Olay, said: ‘The results of the study tell us that exceptional skin ageing is overwhelmingly determined by external environmental and behavioural factors that are within our control, with genetic factors playing a much smaller role.
‘It comes down to smart lifestyle choices, the most important ones being avoiding sun (UV) exposure, and daily sunscreen use to mitigate its ageing effects, keeping the skin well hydrated and having a positive mental attitude.’
The study found women who often or always had dry skin had a 30 per cent lower likelihood of looking young. But the firm said this could include women who failed to moisturise or who naturally had dry skin as their skin type.
There are 2,000 epidermal genes thought to influence how the skin ages, including those involved with DNA repair and replication and cell survival.
The latest research, which judged ‘exceptional agers’ based on whether they were frequently told or believed they looked 10 years younger, will be presented at the annual meeting of the American Academy of Dermatology.