study_id	patient_id	gender	age_years	age_months	date_inclusion	x
x	4	F	2	27	2011-01-01
1	x	F	2	25	2011-01-01
1	1	x	2	27	2011-01-01
1	2	M	x	61	2011-01-01
1	3	F	9	x	2011-01-01
1	3	M	1	17	2011-01-01
1	4	M	2	25	2011-01-01	x
2	1	M	200	32	2011-01-01
2	2	M	3	24	2011-01-01
2	3	F	7	90	2011-01-01
2	4	F	1	14	2011-01-01
2	5	F	2	25	1999-13-01
2	6	M	2	25	1999-12-32