instruction: until 24 months ago, list the monthly average systemicsystolic of patient 008-57160.
response: SELECT AVG(vitalperiodic.systemicsystolic) FROM vitalperiodic WHERE vitalperiodic.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '008-57160')) AND NOT vitalperiodic.systemicsystolic IS NULL AND DATETIME(vitalperiodic.observationtime) <= DATETIME(CURRENT_TIME(), '-24 month') GROUP BY STRFTIME('%y-%m', vitalperiodic.observationtime)