What is the relationship between communicable illnesses and drug use?
Applying the mathematical tools of management science to health care policy, Margaret Brandeau and her colleagues are challenging conventional wisdom about the best strategies for reducing the spread of HIV, hepatitis C and other communicable illnesses.
In particular, they are seeking to understand the relationship between these deadly diseases and illicit drug use.
Can “diversion” programs, which provide alternatives to jail for people arrested for drug possession or prostitution, slow the HIV contagion? Is methadone treatment a cost-effective strategy for treating heroin addiction? Is community-based education more cost-effective than giving prophylactic drugs to people before they have been infected with HIV?
Brandeau, a professor of management science and engineering, has been working with colleagues at Stanford School of Medicine to answer a long list of such questions. The intertwined epidemics of drug addiction and HIV comprise what she calls “nonlinear dynamic systems” — processes that spread at different speeds and in different ways, but can be modeled with mathematical tools.
In a series of papers, funded primarily by the National Institutes of Health, Brandeau and her colleagues have been exploring the most cost-effective ways to decrease the substantial fraction of HIV cases that are spread among people who inject drugs, their sexual partners or their offspring.
The cost-effectiveness of a strategy depends on how many additional years of life it brings to how many people —both people who are infected and those they are at risk of infecting – and how much a particular strategy can drive down the need for future medical care. That requires a complex prediction, drawing on social data about the way people interact with one another, epidemiological data about the chance of transmission associated with different types of interactions, and clinical data about treatments.
“What we’re trying to answer is not how HIV and related diseases spread but the costs and health effects of different policies for controlling these diseases and controlling the harm caused by drug injection,” Brandeau says. A key point, she says, is that there is no single HIV epidemic. In some communities, HIV spreads primarily through injection drug use but is compounded by sexual transmission. In others, it spreads primarily through male homosexual activity. In many African countries, it spreads mainly through heterosexual relations. Thus, the best strategy for controlling HIV in one community may not be the best strategy elsewhere.
Brandeau has been applying her tools to such questions for more than a decade. Back in 2000, she and her colleagues analyzed the cost-effectiveness of methadone maintenance programs. At the time, methadone studies had only focused on the extent to which methadone programs reduced unemployment, criminal activity and emergency room visits for heroin overdoses.
Brandeau and her colleagues asked a different question: Would methadone treatment slow the spread of HIV because it reduced the frequency at which drug addicts injected heroin with dirty needles? The researchers found that methadone treatment substantially slowed HIV infection among addicts and thus the cost of future medical care for AIDS. They estimated that methadone could deliver an extra year of life for about $10,000 – a bargain compared to many other health interventions.
Heroin addiction is now surging again, in part because many people have become addicted to prescription painkillers and sought out heroin as a cheaper alternative. That in turn has led to astonishing surges of HIV in seemingly unlikely communities. Last year, in fact, the Kentucky General Assembly passed legislation allowing municipal governments to launch needle-exchange programs for drug addicts. The state of Ohio is helping fund a number of needle-exchange programs in cities such as Columbus.
In a study last year, Brandeau and her colleagues used mathematical modeling to figure out the best way to allocate scarce budgets for HIV treatment and prevention. Their conclusion: It makes sense to focus first on inexpensive but relatively effective programs such as community-based education, then on rapidly treating infected people with antiretroviral drugs that suppress the HIV virus. A third strategy – giving high-risk people an HIV “pre-exposure prophylaxis” drug before they are infected – was far less cost-effective.
Indeed, the newest paper by Brandeau and her colleagues challenges a current recommendation by the U.S. Centers for Disease Control and Prevention, which calls for HIV pre-exposure prophylaxis for people who inject drugs. Clinical studies indicate that the prophylactic drug (Truvada) reduces a high-risk drug injector’s likelihood of contracting HIV, perhaps by as much as 50%. But Truvada costs $27 per day per person which, if provided to 25% of drug injectors in the United States, would translate to $2.2 billion per year, or 9% of the current federal budget for HIV and AIDS. The cost for a single year of additional life, the researchers estimate, would be $253,000, substantially higher than for most accepted medical interventions.
Brandeau’s newest project is to investigate the health impact of a jail-diversion program called LEAD (Law Enforcement Assisted Diversion), which is currently being pioneered in Seattle. City and county jails in the U.S. process more than 11 million people each year, and the prevalence of communicable diseases such as HIV, hepatitis C and tuberculosis is much higher in jails than in the general population. Brandeau and her team are simulating the flow of at-risk people through the criminal justice system and drug treatment programs, comparing those who get into the diversion program with those who do not. Their goal is to estimate the costs and health benefits of the diversion program, and its impact on public health as well as on the criminal justice system.
“There are many problems of social importance where the tools of operations research and mathematical systems analysis can help improve decision making,” says Brandeau. “We’ve only just begun to scratch the surface.”
