count the number of patients that were diagnosed since 3 years ago with oth/uns inf-cen ven cath.
select count( distinct admissions.subject_id ) from admissions where admissions.hadm_id in ( select diagnoses_icd.hadm_id from diagnoses_icd where diagnoses_icd.icd9_code = ( select d_icd_diagnoses.icd9_code from d_icd_diagnoses where d_icd_diagnoses.short_title = 'oth/uns inf-cen ven cath' ) and datetime(diagnoses_icd.charttime) >= datetime(current_time,'-3 year') )