Forget being over the hill at 40 - you’re now officially 'old' at just 28, a new survey has found. Almost half of all respondents to the survey said 28 was the age they considered to be when they stop being 'young' and finally grow up. Respondents were also asked to nominate the ten most popular changes in behaviour which show that you are no longer young. The most popular answer was the fact that your career becomes more important than your sex life. The second most popular reason was that you prefer listening to BBC Radio 2 rather than Radio 1. Another key pointer to show you have left your youth behind is that you have no idea what is number one in the charts. According to the findings, pop beauty Katy Perry, who turns 28 on October 25, has just over a week left of her youth. Actress Keira Knightley, meanwhile, only has a few months to go, as she turns 28 in March next year. Singer Cheryl Cole, who was 29 in June, is already fast heading to middle age. Dating site www.SeekingArrangement.com polled 1,000 male and female members to find out exactly when youth ends. A total 37 percent of women and 39 percent of men nominated 28 as the key age when you are no longer young. The second most popular answer was 30 - chosen by 27 percent of women and 24 percent of men. TEN SIGNS YOU ARE TRULY GROWN UP 1 Your career is more important than your sex life. 2 You switch from listening to BBC Radio 1 to Radio 2. 3 You want to buy a property rather than rent. 4 You have no idea what is number 1 in the charts. 5 You start looking for a husband/wife rather a boyfriend or girlfriend. 6 You prefer Strictly Come Dancing to X Factor. 7 You would rather go on holiday with a person you are in a relationship with than a group of friends. 8 You would rather cook for yourself than rely on a ready meal or takeaway. 9 You would rather live on your own than share a flat or house. 10 You stop going to nightclubs. 有人说40岁是一个人走向衰老的开始，忘了这句话吧，一项新调查发现，你从28岁就开始正式变老了。 该调查的应答者中有近一半称28岁是他们认为自己不再年轻、终于长大的年龄。 该调查还让应答者说出表明一个人不再年轻的十大行为变化。 最普遍的回答是，一个人的事业开始变得比性生活更重要。 不再年轻的第二大理由是你更喜欢收听BBC第二电台的节目而非第一电台的节目。 另一个表明你已青春不再的重要事实是你完全不知道音乐排行榜第一名的歌曲是什么。 根据这一调查结果，到10月25日就满28岁的流行天后凯蒂•佩里只剩下一周多的青春了。 与此同时，女演员凯拉•奈特利的青春也只余下几个月了，她明年三月就满28岁了。 6月份满29岁的歌手谢丽尔•科尔已经向中年飞奔而去。 约会网站www.SeekingArrangement.com对1000名男女会员进行了调查，以找到青春结束的准确年龄。 共有37%的女性和39%的男性指出28岁是一个人从此不再年轻的关键年龄。 第二大普遍的答案是30岁——有27%的女性和24%的男性选择了这一答案。 表明你真正长大的十个迹象： 1. 你的事业变得比你的性生活更重要。 2. 你收听的广播节目从BBC第一电台换成第二电台。 3. 你想要买房而不是租房。 4. 你不知道音乐排行榜上第一名的歌曲是什么。 5. 你开始找寻丈夫或妻子，而非男友或女友。 6. 你觉得《舞动奇迹》比《英国偶像》更好看。 7. 你更喜欢和自己的恋人一起去度假，而不是和一帮朋友去度假。 8. 你更喜欢自己下厨做饭，而不是吃即食餐或外卖。 9. 你宁愿自己一个人住，而不是和他人合住公寓或房子。 10. 你不再去泡夜店。