My dataset contains ~4000 variables from a survey that collected data on upto 10 members from the same household. (AGE_01, AGE_02...AGE_10/SEX_01, SEX_02.... SEX_10/BMI_01, BMI_02.....BMI_10).

Is it possible to keep only the FIRST observation for all the variables (AGE1, SEX1, BMI1) by dropping the rest.