The Puerto Rico Health Insurance Administration (ASES) contracts with private managed care organizations to provide health care services for approximately 1.5 million people, or 40% of the population of Puerto Rico. We examined the impact of the vintage (original FDA approval year) of drugs used to treat a patient on the probability of survival, conditional on demographic characteristics (age, sex, and region), utilization of medical services, and the nature and complexity of illness, using ASES data covering over half a million people. I could not control for education and income, but to be eligible for Medicaid in Puerto Rico, annual income of a family of four could not exceed $16,440 (in the year 2002).

We found that ASES beneficiaries using newer drugs during January-June 2000 were less likely to die by the end of 2002, conditional on the covariates. The estimated mortality rates are strictly declining with respect to drug vintage. For pre-1970 drugs, the estimated mortality rate is 4.4%. The mortality rates for 1970s, 1980s, and 1990s drugs are 3.6%, 3.0%, and 2.5%, respectively. The differences in mortality rates are highly statistically significant (p-value < .0001).

The actual mortality rate is about 16% (3.7% vs. 4.4%) lower than it would have been if all of the drugs utilized in 2000 had been pre-1970 drugs. This suggests that new drugs introduced during 1970-2000 reduced the mortality rate by about 0.58% per year. This is not implausible, in light of the time-series data on mortality. The introduction of new drugs appears to have accounted for a significant fraction of the long-run decline in Puerto Rican mortality.

Percentages of post-1980 and post-1990 Rx’s are much lower in ASES than they are in U.S. Medicaid. The estimates imply that if the ASES vintage distribution were the same as U.S. Medicaid’s, ASES’s mortality rate would have been 5.3% lower (3.5% vs. 3.7%). Use of older drugs in Puerto Rico’s Medicaid program may be partly attributable to the fact that, in Puerto Rico, the physician bears the costs of the drugs—the cost is deducted from the physician’s capitation payment.

In addition to estimating the model for the entire ASES population, we estimated the model separately for three groups: people with diseases of the circulatory system; people with endocrine, nutritional and metabolic diseases, and immunity disorders (primarily diabetes); and people with neoplasms. With only one exception, within each group the coefficients of all three drug-vintage variables were negative and highly significant.

In this study, we did not control for the effect of the vintage of medical products and services other than drugs on survival, and this may have affected our estimates of the effect of drug vintage. We plan to address this issue in future research.

Category: EFFECT OF DRUG VINTAGE / Tags: Clinical studies, myocardial infarction, survival rates