The study included data on 315 adults aged 65 years and older, representing a recruitment rate of 43%. Comparison of respondents and non-respondents was possible for a limited number of variables. Those who declined to participate were similar to those included in the study in age (77.1 years vs. 73.7 years, p = 0.27), gender (74.3% vs. 76.3% female, p = 0.51), and ethnicity (49.3% vs. 51.6% Hispanic, p = 0.52). The percent of African-Americans who declined (33.1%) and those who participated (16.4%) was different (p < 0.0001).
Among study participants, more than half (50.1%) had house-hold incomes at or below $750 per month, and more than half (59.9%) had Medicaid coverage (). As expected with patients seen in a hospital-based outpatient practice, poor health and heavy illness burden were common. Sixty percent reported fair or poor general health and 26.8% reported having five or more chronic illnesses. Although 51.1% reported routinely using six or more prescription medications, only 12.3% reported out-of-pocket prescription costs in excess of $100 per month due to the predominance of Medicaid beneficiaries in the study sample.
Patient characteristics (n = 315)
3.1. Scale performance
The 4-item scale of beliefs about generics had a mean of 14.2 (S.D. 4.0), median of 14 (range 4-20), and followed an approximately normal distribution (kurtosis -0.35 and skewness -0.35). The mean belief score was not significantly higher after January 1, 2006 when USA implemented the voluntary prescription drug benefit (Medicare Part D) for older (≥65 years) and disabled adults in the federal Medicare health insurance program (pre- vs. post-implementation of Part D, mean score 13.9 (4.1) vs. 14.5 (4.0); p = 0.21). The scale demonstrated concurrent validity: having a preference for brand name medications and having requested a brand name agent were both significantly associated with negative beliefs about generic drugs (p = 0.0001 and p = 0.02, respectively).
3.2. Beliefs about generic drugs
shows the frequency of responses to each item used to assess beliefs about generics. Fewer than half of respondents reported that generics are as effective or as safe as brand name drugs or have the same number of side effects. In contrast, only 3.8% of respondents disagreed that generics are less expensive than brand name drugs. Many study participants were uncertain about whether generic and brand name drugs are equivalent in terms of effectiveness, safety, ease of use, side effects, and cost. For example, 19.4% were uncertain whether generics were less expensive than brand name drugs and 41.8% were uncertain whether generics have more side effects.
Self-reported beliefs about generic drugs (n = 315)
Unfavorable views of generic medications were more common among those of lower socioeconomic status (). Unfavorable views were associated with non-white race, lower education, lower levels of health literacy and lower income, having Medicaid, worse functional status, and worse physician communication scores. Age, sex, English language proficiency, health status, and out-of-pocket prescription drug spending were not statistically associated with views about generic drugs.
Multivariable analysis of correlates of generic drug beliefs
In multivariable linear regression analysis (), only black race and inadequate health literacy were significantly associated with negative beliefs about generics (black race, β = -2.00, p = 0.03; inadequate health literacy, β = -2.06, p = 0.001). Poor physician communication skill was associated with negative beliefs about generics, although the association did not achieve statistical significance at all levels of communication scores.
shows the domains of the beliefs about generic drugs scale, as well as beliefs about generic drug costs, stratified by level of health literacy. In this analysis we dichotomized the belief domains as disagree vs. uncertain or agree to facilitate interpretation of the data. Health literacy was significantly associated with all domains of beliefs about generic drugs. Individuals with inadequate health literacy were nearly half as likely to question their effectiveness and half as likely as those with marginal or adequate health literacy to say that generics are as safe as brand name drugs.
Percent agreement with statements about generic drugs, stratified by health literacy
These associations remained statistically significant in multivariable logistic regression analyses (). Individuals with inadequate health literacy had less than half the odds of those with adequate health literacy of reporting that generics work as well as brand name drugs. In other words, study participants with inadequate health literacy were more likely to question the effectiveness of generic drugs. They were also more likely to agree that generics have more side effects than brand name drugs.
Adjusted association of health literacy with individual beliefs about generic drugs
Regarding racial differences in beliefs about generic medications, black adults were significantly less likely than whites to state that generics work as well as brand name drugs (adjusted OR 0.28, 95% CI 0.10-0.79, p = 0.02). They were also less likely to say that generics are as safe as brand name drugs (adjusted OR 0.38, 95% CI 0.14-1.05, p = 0.06) and more likely to say that generics are more difficult to take (adjusted OR 2.78, 95% CI 0.94-8.19, p = 0.06), though these associations did not reach the level of statistical significance. In adjusted analyses, black race was not significantly associated with beliefs about the costs or side effects associated with associated generic drugs.