How about this..............
DECLARE @BIRTH_DATE DATETIME, @STPR_START_DATE DATETIME
SET @BIRTH_DATE = '2008-02-29'
SET @STPR_START_DATE = '2013-02-28'
SELECT CASE WHEN YEAR(@STPR_START_DATE)%400 != 0 AND DAY(@STPR_START_DATE)= 28 THEN
DATEDIFF(YEAR, @BIRTH_DATE, @STPR_START_DATE) - CASE WHEN MONTH(@BIRTH_DATE)*100 + (DAY(@BIRTH_DATE) -1) > MONTH(@STPR_START_DATE)*100 + DAY(@STPR_START_DATE) THEN 1 ELSE 0 END
ELSE
DATEDIFF(YEAR, @BIRTH_DATE, @STPR_START_DATE) - CASE WHEN MONTH(@BIRTH_DATE)*100 + DAY(@BIRTH_DATE) > MONTH(@STPR_START_DATE)*100 + DAY(@STPR_START_DATE) THEN 1 ELSE 0 END
END AS AGE