Table 1 Overview of studies reviewed (in alphabetical order)

Adams, Soumerai, & Ross-Degnan, 2001a

4439 Medicare beneficiaries with hypertension

national longitudinal survey (MCBS 1995); inferential statistic

Association between types of drug coverage, consumption & costs per tablet; Findings: income

Blustein, 1995a

4110 female Medicare beneficiaries

probability survey based on multistage, stratified cluster sample of Medicare (MCBS 1991-1992); multiple inferential statistic

Use of mammography during first 2 years of Medicare offered benefit; Findings: income, education

Blustein, 2000b

4334 Medicare beneficiaries with hypertension

nationally-representative face-to-face survey of Medicare; multiple inferential statistic

Sexual differences in burden for prescription drugs; Findings: sex

Chandra et al., 2007

70912 CalPers plan members

Panel of Medicare supplemental plan Members (CalPers 2000-2003); multiple inferential statistic

Influence & consequences of price elasticity in patient cost-sharing; Findings: income

Crystal, Johnson, Harman, Sambamoorthi, & Kumar, 2000b

7886 Medicare beneficiaries

nationally representative survey of Medicare, stratified, multistage, area probability sample (MCBS 1995); multiple inferential statistic

Overview on size, distribution & burden of OOPP; Findings: income, education

Davis, Poisal, Chulis, Zarabozo, & Cooper, 1999a

12.000 Medicare beneficiaries

Panel Survey (MCBS 1995); descriptive

Overview on sources & extent of drug coverage among Medicare beneficiaries; Findings: income

Dowd et al., 1994a

2891 Medicare HMO & fee-for-service members

Survey; multiple inferential statistic

Characteristics of Medicare beneficiaries & influence on choice of health plan; Findings: income

Fahlman, Lynn, Doberman, Gabel, & Finch, 2006d

4602 Medicare beneficiaries

Cross-sectional, retrospective review & 1990 Census data; multiple inferential statistic

Drug spending by disease & demographics in last year of life; Findings: income

Gellad, Huskamp, Phillips, & Haas, 2006a

5596 Medicare beneficiaries

Panel Survey, nationally representative sample (MEPS-HC 1996-2000); multiple inferential statistic

Estimation of change of OOPP for drugs after Part D implementation; Findings: income

Goldman & Zissimopoulos, 2003b

7836 Medicare beneficiaries

Cross sectional survey of 4th wave of Panel survey (HRS 1998); inferential statistic

Examination of OOPP health-care spending; Findings: income

Guidry, Aday, Zhang, & Winn, 1998b

593 Texan cancer patients

analytical cross-sectional survey; inferential statistic

Prevalence of barriers to cancer treatment; Findings: income

Hwang, Weller, Ireys, & Anderson, 2001a

22.326 patients with chronic condition

cross-sectional survey (MEPS 1996); descriptive

Impact of chronic condition & demographics on OOPP spending; Findings: sex

Klein, Turvey, & Wallace, 2004i

6535 participants of AHEAD-study

cross-sectional study of 2nd wave of AHEAD study 1997; inferential statistic

Reasons for delay in medication use because of cost; Findings: income, sex

Lapsley, March, Tribe, Cross, & Brooks, 2001a

113 patients with osteo-arthritis in Australia

prospective-cohort study; inferential statistic

OOPP expenditures related to osteo-arthritis; Findings: sex

McGarry & Schoeni, 2005b

3821 >70 years old Americans (271 widowers, 3550 married)

national panel survey (2 Waves) (HRS); descriptive

Financial gap between widowed and married Elders; Findings: sex

Miller & Champion, 1993a

161 women

convenience sample, mailed survey; inferential statistic

Relationship of patient's characteristics and mammography utilization; Findings: income, education

Mitchell, Mathews, Hunt, Cobb, & Watson, 2001a

499 patients with at least one regular prescription medication

cross-sectional survey; mutliple inferential statistic

extent of mismanaging of prescription drugs among rural Elders; Findings: income

Mojtabai & Olfson, 2003c

10.413 Medicare beneficiaries

cross-sectional (HRS 2000); multiple inferential statistic

Association between drug coverage & adherence; cost-related poor adherence & health outcomes; Findings: income

Ness, Cirillo, Weir, Nisly, & Wallace, 2005b

1099 participants of HRS study

cross-sectional (HRS 2000); inferential statistic

Correlates of complementary & alternative medicine (CAM) utilization among Elders; Findings: sex

Pourat, Rice, Kominski, & Snyder, 2000d

15.103 Medicare beneficiaries

cross-sectional (MCBS 1996); inferential statistic

Comparison of supplemental insurances to examine impact of socioeconomics; Findings: income, education

Rector & Venus, 2004a

1500 Medicare+Choice plan beneficiaries

cross-sectional, random sample in eight Medicare+Choice Plans; inferential statistic

Influence of drug benefits on affordability for beneficiaries; Findings: income

Rice & Desmond, 2006e

9278 Medicare beneficiaries

cross-sectional (SIPP 2001); descriptive

Number and characteristics of Medicare beneficiaries excluded from low-income subsidies because of failed asset test; Findings: education, sex

Riley, 2008b

4000 Medicare beneficiaries at a time

panel 4 waves (MCBS 1992, 96, 2000, 04); inferential statistic

Trends in OOPP health-care costs for MediCare beneficiaries; Findings: income

Rogowski, Lillard, & Kington, 1997b

996 Elders

cross-sectional (PSID 1990); multiple inferential statistic

Amount & influence of supplemental insurance on burden of prescription drug OOPP costs; Findings: income, education, sex

Sambamoorthi, Shea, & Crystal, 2003b

8814 Medicare beneficiaries

cross-sectional (MCBS 1997); multiple inferential statistic

Total and OOPP burden for prescription drugs in relation to characteristics of elderly population; Findings: income, education

Saver, Doescher, Jackson, & Fishman, 2004d

4492 Medicare+Choice enrollees

cross-sectional survey and administrative data from Medicare, 2000; multiple inferential statistic

Relationship between drug benefit status & access to medications + influence of income; Findings: income, education

Selden & Banthin, 2003b

5733 (1987), 2549 (1996) >65 years old beneficiaries

stratified random samples (NMES 1987 and MPES 1996), longitudinal; descriptive

Amount health-care burden for Elders; Findings: income, sex

Soumerai et al., 2006a

13.835 Medicare beneficiaries

stratified, multistage sample (MCBS 2004), cross-sectional; multiple inferential statistic

Prevalence of cost-related medication non-adherence prior to Medicare Part D; Findings: income

Wei, Akincigil, Crystal, & Sambamoorthi, 2006a

76.440 person-years (30.375 beneficiaries) of Medicare beneficiaries

longitudinal (MCBS 1992-2000); multiple inferential statistic

Gender differences in OOPP expenditures & burden for medication; Findings: sex