Ben Stiller finds it difficult staying relevant.

The Hollywood star will turn 50 in November and admitted he has found ageing tough because he always wants to stay current.

He confessed: ''It's hard to stay current to whatever the current hipster hipness is.

''Pop culture moves so quickly now and people's attention spans are so short.''

The 'Night at the Museum' actor says getting older has been particularly difficult in the last few years, as it has felt like time has being moving quicker, and he is unable to remember as much as he did as a youngster.

He explained: ''I'm just amazed as I get older how time - you know that thing of how time goes faster? - I definitely feel that. And being able to hang on to the experience of things, I find that a little bit harder, too. Retaining memories.''

However, Ben - who has 12-year-old daughter Ella and nine-year-old son Quinlin with wife, actress Christine Taylor - revealed he is hoping to revisit his youthful side in the sequel to his popular 2001 film 'Zoolander', which he is directing and starring in.

Speaking to the Daily Telegraph newspaper's review section, he added: ''I've never directed a sequel - you want to try to make something that's fresh and new and also honours what people loved about the first one. I'm just trying to go back to what makes us laugh.''