###HUMAN: what is patient 015-7988's first diagnosis until 4 years ago?, ###ASSISTANT: SELECT diagnosis.diagnosisname FROM diagnosis WHERE diagnosis.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '015-7988')) AND DATETIME(diagnosis.diagnosistime) <= DATETIME(CURRENT_TIME(), '-4 year') ORDER BY diagnosis.diagnosistime LIMIT 1