I think I want to downtune my guitar to A standard (from E standard), do I need a higher gage of strings to do this?

Short answer yes.

Longer answer. That's going to be really difficult.

First you'll need heaviest strings you can find I'd suggest. Then you're probably going to find the nut will need adjusting, ie the slots widened to accommodate the new gauge of strings.

Even then A is a very long way down. I have some standard guitars tuned down to Eb standard or D standard. But any lower I'd recommend getting a baritone guitar with longer scale. This helps keeps the strings at a tension that is OK to play too short a scale and whatever gauge of strings they will just be too floppy to hold tune, intonate correct and sounds OK.

A Baritone with a longer scale preferably a 30" scale as your dropping a tone from even a standard Baritone tuning of B standard.

Another alternative would be a 7 string, again string with heavy gauge strings and drop it all a tone. Then essentially on the bottom six strings you'll have A standard sort of.