Age is not a factor to consider for that specific subject. You know what REALLY makes think he's around 38 or older? His voice. Just like when you're in puberty and suffer from a change in your voice, it happens again when your body begins to decline. If you listen carefully (and taking aside how much they smoke) you can see the difference in Hyde's voice which is now rougher.. there are many singers who suffer from this, which is natural, but it won't happen on early 30's.
When you have followed a singer's career, you can tell the difference in his voice. Gackt's nasal voice this days is not an experiment, I can tell you that.
I also think he's had surgery. Not as dramatic as some like to paint it, but some, you know, to help the eye area and things... ARGH!!! is so hard for me to explain in english!!!!!