How to get exact year difference between two dates in SQL Server?
Subtract one from each other in YYYYMMDD format, and divide by 10000 using integer division (which rounds down).

So:

(YEAR(@CurrentDate) * 10000 + MONTH(@CurrentDate) * 100 + DAY(@CurrentDate)
- YEAR(@DateOfBirth) * 10000 - MONTH(@DateOfBirth) * 100 - DAY(@DateOfBirth)
) / 10000


20150725-20000727 = 149998, and 149998 / 10000 = 14

You can also use CONVERT(int,CONVERT(char(8),@CurrentDate,112)), because style 112 is YYYYMMDD, but that's a little obfuscated in my opinion.