Multiple scores per subject

This may be a simple question, but I am new here.

I am doing a linear regression in which I have a number of subjects but each subject has multiple dependent variable scores (single variable, multiple scores per subject, not repeated measure), and each subject does not have the same number of these dependent scores. I want to see if factors like age or BMI impact these scores, but to do this in SPSS I would have to enter the subjects age and BMI multiple times in the same row as their dependent scores. My concern is that this is counting these factors multiple times, and an unequal number of times. Simply put a subject with 6 scores would have their age entered 6 times and a subject with 4 scores would have their age entered only 4 times.

Can I do this?