Do Men and Women React to Information on HIV Risk Differently?

This is the meta-subject of a new paper in PLoS ONE by myself and my buddy/co-author Brendan Maughan Brown. Here is the abstract, which mostly explains everything:

Objectives
We examined whether knowledge of the HIV-protective benefits of male circumcision (MC) led to risk compensating behavior in a traditionally circumcising population in South Africa. We extend the current literature by examining risk compensation among women, which has hitherto been unexplored.

Methods
We used data on Xhosa men and women from the 2009 Cape Area Panel Study. Respondents were asked if they had heard that MC reduces a man’s risk of contracting HIV, about their perceived risk of contracting HIV, and condom use. For each gender group we assessed whether risk perception and condom use differed by knowledge of the protective benefits of MC using bivariate and then multivariate models controlling for demographic characteristics, HIV knowledge/beliefs, and previous sexual behaviors. In a further check for confounding, we used data from the 2005 wave to assess whether individuals who would eventually become informed about the protective benefits of circumcision were already different in terms of HIV risk perception and condom use.

Results
34% of men (n = 453) and 27% of women (n = 690) had heard that circumcision reduces a man’s risk of HIV infection. Informed men perceived slightly higher risk of contracting HIV and were more likely to use condoms at last sex (p<0.10). Informed women perceived lower HIV risk (p<0.05), were less likely to use condoms both at last sex (p<0.10) and more generally (p<0.01), and more likely to forego condoms with partners of positive or unknown serostatus (p<0.01). The results were robust to covariate adjustment, excluding people living with HIV, and accounting for risk perceptions and condom use in 2005.

Basically, our results show that women react to information on circumcision's protective benefits in a manner consistent with risk compensation, which is a phenomenon where individuals undertake risky behaviors if they feel that they are protected from its consequences somehow. Why do women respond differently from men? We aren't sure, but we theorize that it could be related to (some combination of):

-Misinformation among women about the protective benefits of circumcision as far as male-to-female HIV transmission (circumcision has only been shown to impact female-to-male transmission).
-Lack of opportunities for women to discuss circumcision, sex, and HIV in public places.
-Higher prior probabilities of contract HIV in women (which means risk information will be more likely to shift beliefs about HIV on the margin - good ole' Bayes's Theorem)
-A sense of reduced need among women to have to negotiate condoms, which could be tricky in a world where there is imbalance in power across genders.

Some new research by other groups (more on this in a later post) provides evidence that the first of these could be at play. Watch this space for more, as we attempt to find some explanations!

PEPFAR on the Mind

The July 31st issue of Health Affairs devotes itself to the President's Emergency Plan for AIDS Relief (PEPFAR) and explores the aid program from a number of interesting viewpoints. The highlights for me includes a piece by Harsha Thirumurthy and coauthors on the economic benefits of treating HIV and a wonderful piece of research by Karen Grepin examining the effects of PEPFAR aid on other domains on health care (she finds positive spillovers for certain maternal health services, but crowd-out for child vaccines). The article by John Donnelly discusses the origin of PEPFAR within the (W) Bush administration, which I am sure would make most send some positive vibes to this otherwise beleaguered president.

The articles on the future of PEPFAR (how the funding streams can be better targeted, how much funding is needed and for how much longer) are quite interesting, as well. Certainly, if you have a particular interest in PEPFAR, the whole issue is worth reading.

Global Health Focus in This Week's JAMA

Some interesting new op-ed and research pieces on global health in the latest issue of JAMA. Perhaps the most interesting is this piece by Eran Bendavid and co-authors, who examine PEPFAR (The United States President's Emergency Plan for AIDS Relief) and its impact on all-cause mortality in Africa. This is important because some have argued that intense spending on HIV in this manner has crowded out spending on other important health problems. The authors use a differences-in-differences strategy (comparing mortality rates within countries before and after PEPFAR, with some areas getting funding and others not as much, holding context fixed factos across countries) and find that increased PEPFAR funding was associated with lower all cause mortality rates. (HT: Paula Chatterjee)

Preventing HIV and STDs with Cash Transfers - Both Abroad and Here?

So on the heels of my post a few days ago comes a brand new study in The Lancet where women in Malawi randomized to receive unconditional cash transfers were less likely to contract HIV or other STDs than their unpaid counterparts. Here is a very nice summary piece on the study.

The mechanism linking cash transfers to reduced HIV may have something to do with the fact that women with access to such resources need not depend on men for the same. That is, women who are cash strapped or who lack opportunities in the labor market may need to depend on relationships where the partner can support them financially. Financial support, in turn, may reduce their ability to negotiate safe sex practices (this is the so-called "transactional sex").

Cash transfer programs of this nature may not just be useful overseas. A forthcoming article in the Journal of Adolescent Health shows that young African American women in Atlanta who have boyfriends who give them gifts are less likely to use condoms than those without such boyfriends or those with boyfriends who go on to find another source of spending money. The authors conclude that "receiving spending money from a boyfriend is common among adolescent women in populations targeted by pregnancy and sexually transmitted infection prevention interventions, and may undermine interventions' effectiveness." (HT: Paula C for the Atlanta paper).

Male Circumcision, HIV/AIDS and the "Real World"

This past week, PLoS Medicine put forth multi-piece expose (start with this lead/summary article) on medical male circumcision, its cost-effectiveness in combating HIV/AIDS and methods and challenges to scaling up this practice in Sub-Saharan Africa, where the epidemic is at its worst. The upshot of this series of papers was covered in a recent Scientific American piece (which quotes yours truly). To summarize, the argument is that medical male circumcision works (as demonstrated in three large randomized clinical trials, all conducted in Africa) and is cost-effective. Indeed, it may even be cost-saving, with high upfront costs that are easily recovered over a 10 year period. Challenges to scale-up include finding health care workers to carry out circumcisions (in a way that doesn't crowd-out provision of other important health care services), getting people to adopt the practice in a respectful, non-coercive yet effective way, especially in areas where there are strong traditional norms over circumcision, and dealing with any risk compensating behavior (if circumcised individuals think circumcision is protective, they may be more likely to engage in riskier sexual behaviors than they otherwise would - more on this in a later post).

Circumcision is one of those topics that seems to always bring with it a vociferous debate. Those opposed to the practice make their stance known quite vehemently. In my opinion, much of what is being spouted against medical male circumcision as a tool for HIV prevention is based on an incomplete understanding of the available evidence and already strong negative priors against the practice that are almost impossible to shift (for example, see this clip or refer to any of the comments to the aforementioned Scientific American article).

However, I think there is one oft-cited argument against medical male circumcision that is worth discussing further. In particular, opponents point to evidence from a 2009 UNAIDS study that uses recent survey data from 18 African countries and concludes that "there appears no clear pattern of association between male circumcision and HIV prevalence—in 8 of 18 countries with data, HIV prevalence is lower among circumcised men, while in the remaining 10 countries it is higher." This is contrast to the large randomized clinical trials mentioned above which show that circumcision reduces HIV rates by greater than 50%. The fact that the clinical trial results are not borne out in the sample survey data, opponents argue, means that circumcision does not work in "real world settings."

In a recent study, Brendan Maughan-Brown, Nicoli Nattrass, Jeremy Seekings, Alan Whiteside and I offer a different explanation for this differential set of findings. It has to do with the fact that the UNAIDS study looks at population that were circumcised in a multitude of settings (clinics, traditional healers) whereas the clinical trials focus on medical circumcision only. In practice, there great deal of heterogeneity in traditionally circumcising populations: some people do not have all of their foreskin removed, and others are circumcised several years after their peers. In our study population of blacks living in the Cape Town metro area, when we don't account for this heterogeneity, we find only a weak negative effect of circumcision on HIV positivity. However, once we "unpack" circumcision, we find that the practice actually has a strong negative association with the probability of testing HIV positive, provided it is done earlier and that there is complete removal of the foreskin.

These results suggest that the UNAIDS results may simply be due to measurement error. In a traditional setting, a circumcision is not a circumcision is not a circumcision. Treating every circumcised person the same introduces measurement error, and statistically it is well known that this would deflate the estimates of the impacts of the practice towards zero. So, the differential results between the UNAIDS findings and the randomized clinical trial findings is not that circumcision doesn't work in the real world. Rather, it is that we really need to understand better the heterogeneity in male circumcision and what can be done to ensure better outcomes for everyone involved.

Sex and Measurement

We know with a good deal of certainty that unprotected sex exposes individuals to potentially life-threatening illness. We also know that all sexual encounters are not the same and, especially since the HIV/AIDS epidemic, researchers have been trying to figure out what sexual behaviors are riskiest and how to use this information towards better micro and macro-focused prevention efforts.

As with all research, a key issue is measurement. Our models to predict individual behavior are usually only as good as our data. As you might imagine, sex can be a personal topic. One may be reluctant to tell a survey interviewer/doctor/friend about their sexual activities, obscuring the whos, hows and whens that are oh-so-important for public health.

Some recent work provides insight into the scale of the measurement problem. A paper by Alexandra Minnis and colleagues compared self-reported sexual activity with biomarkers of exposure (a test based on PSA which can detect exposure to semen in the previous two days) in a sample of Zimbabwean women. The results were sobering: 52% of women who had positive biomarkers said that they engaged in protected sex in the last two days; 23% reported having no sex at all!

In another paper, Brendan Maughan-Brown and I looked at a sample of young adults in Cape Town, South Africa. Our study focused on concurrent sexual partnerships, intuitively defined as the presence of (temporal) overlap between sexual relationships with two distinct partners. There is a hot debate right now on whether such partnerships have been driving the HIV/AIDS epidemic in sub-Saharan Africa. Unfortunately, this debate has been held back by the availability of good data.

Recently, UNAIDS came out with some guidelines on how to standardize and better measure concurrency. We assessed the effectiveness of these guidelines by assessing whether individuals who reported having concurrent relations also reported more than one sexual partner. What we found was surprising: among those who reported only one sexual partner in the last year, nearly 1 out of 6 reported having concurrent sexual relations during this period! We conclude that the UNAIDS methods, which involves asking individuals about each sexual partner they've had and the start and end dates of those partnerships, may actually underestimate the prevalence of concurrency by a significant amount by not fully accounting for all sexual partners.

As both these papers suggest, we have a long way to go before we can credibly claim that we have precise, unbiased estimates of sexual behavior. It would be useful to divert some of time we all spend on linking specific sexual behaviors to health outcomes to figuring out how to get the measurements of those behaviors right in the first place.

Economic Shocks, Risky Sexual Behavior and the HIV/AIDS Epidemic

The relationship between poverty and HIV/AIDS is a tricky one to pin down empirically. Studies have found widely different associations between SES and the likelihood of having been infected, though the positive association between education and HIV risk appears to be stable across time and space (see this excellent paper by Jane Fortson).

Aside from permanent economic status, transitory shocks may have some impact on the HIV/AIDS epidemic, as well. The idea is that bad times may induce people to engage in riskier sex because of market returns to such behaviors. The possibility of transient shocks in driving sexual behavior and, consequently, the HIV/AIDS epidemic is an intriguing one, especially given the potential prominence of "transactional sex" - sex in exchange for gifts, favors, etc (i.e., not necessarily prostitution!) - in African countries.

Two recent papers having examined this issue in the context of commercial sex workers. A study by Pascaline Dupas and Jonathan Robinson looks at the effects of political instability in Kenya circa 2007, which led to civil conflict and adverse economic times, on the behavior of commercial sex workers (CSWs). They find that CSWs were more likely to engage in unprotected sex after the adverse shock. A paper by Robinson and Ethan Yeh tells a similar story: CSWs in Kenya were more likely to have a variety of different types of riskier sex in response to income shocks. Both of these studies are well done from the stand point of data collection (how many people have panel data on CSWs??) and statistics (causality is plausibly inferred from both pieces).

In some African countries, however, CSW is not a common practice while transactional sex, more broadly, is. In such areas, it would be interesting to look at how the sexual behaviors of the general population respond to income shocks. My colleague Brendan Maughan-Brown, from the University of Cape Town, and I are working on this in the context of Khayelitsha, a township of Cape Town, SA, where antenatal clinic data indicates an HIV/AIDS of over 30%. Using longitudinal data from an effectively random sample of the township, we found (from individual fixed effects models) that people responded to income shocks by reducing condom usage. Interestingly, we found the same result when looking at individuals who were on anti-retroviral therapy for HIV/AIDS (draft forthcoming - will keep you posted).

We are currently trying to understand whether our results reflect a price mechanism (individuals cannot afford to pay the cost of obtaining and using condoms during bad times) or a consumption smoothing mechanism (individuals engage in riskier sex to get by during bad times). Either way, we have compelling evidence that economic shocks may play a role in driving the HIV/AIDS epidemic.

Now Online: My Talk on Disability Grants and Adherence to HAART in South Africa

You can find it here (you'll need RealPlayer or RealAlternative to view it). Here is a description of the study, conducted by myself, Brendan Maughan-Brown (University of Cape Town), Nicoli Nattrass (University of Cape Town) and Jennifer Ruger (Yale) from a previous post.

We are currently working on a new draft of this paper and should have that ready in a week or so. In the meantime, I'd love to hear your comments on how to improve upon this study.

HIV/AIDS and the Erosion of Medical Care

A new and important paper by Anne Case and Christina Paxson finds the following:

We document the impact of the AIDS crisis on non-AIDS related health services in fourteen sub-Saharan African countries. Using multiple waves of Demographic and Health Surveys (DHS) for each country, we examine antenatal care, birth deliveries, and rates of immunization for children born between 1988 and 2005. We find deterioration in nearly all of these dimensions of health care over this period. The most recent DHS survey for each country collected data on HIV prevalence, which allows us to examine the association between HIV burden and health care. We find that erosion of health services is highly correlated with increases in AIDS prevalence. Regions of countries that have light AIDS burdens have witnessed small or no declines in health care, using the measures noted above, while those regions currently shouldering the heaviest burdens have seen the largest erosion in treatment for pregnant women and children. Using semi-parametric techniques, we can date the beginning of the divergence in health services between high and low HIV regions to the mid-1990s.

Case and Paxson are unable to pin down a mechanism for why this is happening. They suggest it is not driven by an erosion of wealth (though the data they use is somewhat lacking in measures of health beyond asset ownership) or reduced demand for medical care by HIV+ mothers. On the other hand, they cannot rule out adverse impacts of HIV/AIDS on the supply of health care workers and/or the diversion of resources to those with HIV/AIDS, perhaps at the expense of other aspects of medical care. As such, the authors rightly point out that there is more work to be done and that this work needs to be done very soon.

I'll have more to say about this in a forthcoming post.

Shaan's Blog and Swine Flu

My friend, former tennis partner and former Yale MPHer Shaan Chatturvedi has just started blogging about his experiences in Guyana, where he is currently a working for the CDC Global AIDS Program. His most recent post, on the swine flu outbreak, is fantastic and promises of good things to come from his blog. Do check it out!

For more on the swine flu, check out this interesting article by Dr. Carlos del Rio, the chair of the Global Health Department of the Emory School of Public Health. There is a lot of interesting stuff in there about different control measures and the reasons why swine flu mortality might be higher in Mexico than in the US.

Kenya to Deworm, Female Bank Robbers and Other Random Links

I'm in full-scale dissertation writing mode, so all you're getting from me between now and March 16th are links (if that). Enjoy!

1. Kenya has decided to roll-out a nationwide, school-based deworming program. The impetus for this likely came from some now famous experimental research carried out by Poverty Action Lab researchers Edward Miguel and Michael Kremer, showing that deworming (a) has large effects on school attendance and that these impacts are underestimated if one doesn't account for externalities (i.e., worms are infectious) and (b) is a highly cost effective way to improve schooling.

2. Martin Anderson, a former Yale MPHer and now a PhD student in Health Economics at Harvard, has started writing for the Social Science Statistics Blog (linked in the sidebar). His first post, on Medicaid drug procurement and the market for pharmaceuticals, is awesome.

3. Will tax credits stimulate the economy? Evidence from 2008 suggests not.

4. The number or share of bank robberies committed by women: a new leading or coincident indicator?

"Dakar to Port Loko"

I recently went to a screening of Yale political science graduate student Nathaniel Cogley's extremely well-done and worthwhile documentary "Dakar to Port Loko: Perspectives from West Africa". I highly recommend this film. Nathaniel spent a few years in West Africa after college, camcorder in tow, with his goal being to "let Africans speak for themselves." And, boy, do they: the film covers everything from opinions on US international policy, to civil war, to microcredit. It's eye opening stuff all around.

Chris Blattman with more about the film and Nathaniel's very interesting background (as well as video of the film's trailer).