Retrospective Studies human 43 retrospective study 43 Article 42 Humans 42 female 40 male 40 major clinical study 38 Female 35 Male 35 Middle Aged 30 middle aged 30 United States 29 aged 29 controlled study 29 cohort analysis 28 adult 27 Aged 25 health care cost 25 economics 24 health care utilization 19 Adult 18 Aged, 80 and over 17 Health Care Costs 17 medicare 17 very elderly 17 follow up 16 Medication Adherence 15 medication compliance 15 insurance 14