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‘Scoping’ location: the role of ‘place’/’space’ as an influence on HIV outcomes amongst young MSM

14 Mar, 17 | by Leslie Goode, Blogmaster

Bauermeister & Stephenson (B&S) is a scoping review addressing the impact of location – ‘space’ and ‘place’ – on HIV prevention and care outcomes for young MSM (YMSM).  It owes much to Diaz & Ayala and their concern to view human behaviour in terms of ‘social location’ ‘within a context of social oppressive factors’ rather than in terms of ‘individual identity’.  It focuses on 17 studies, selected for inclusion much as in a systematic review, but analyzed according to scoping methodology (i.e. with a view to mapping out the investigative territory rather than addressing a specific question).  Social location is translated by this study into concepts of ‘space’ and ‘place’.  Space here refers to the physical and geographical aspects of location such as proximity to services and transportation, and place to more socially constructed aspects – ‘the interpersonal exchanges and dynamics that result in physical and social resources in space’.

It is perhaps on account of the breadth of these goals and the methodology of scoping that no very conclusive findings emerge.  Where location assumes the more geographically defined characteristics of ‘space’, the findings underscore the importance of geographic information system (GIS) approaches (see also: Simms & Petersen (STIs editorial); Petersen & Simms (STIs)).  But elsewhere – especially where the concept of location shades into less physical definitions of context (i.e. ‘place’) – the evidence is more contradictory and sometimes appears counter-intuitive.   For example, there are studies that find a positive correlation between social disadvantage and higher levels of adherence to HIV prevention and care recommendations.  Apparently, however, income inequality (as measured by Gini ratio or male-to-female ratio of earnings) stands out across studies as an indicator of poorer YMSM outcomes.

In discussing the limitations of their study, the authors make the interesting point that in a field of investigation as hard to define and as open to fresh hypotheses as this, the tendency for studies reporting an insignificant or null finding not to make their way into the literature could contribute to a serious distortion of our understanding (i.e. ‘publication bias’).  As is evident from their discussion of the review findings, well-conducted studies reporting non-significant findings on the influence of location can make a valuable contribution to the debate (such as, for example,  Haley & Cooper (STIs), a paper published online on the related issue of influence of location on STIs).

A second intriguing question is raised by this review, even if it is perhaps not adequately discussed in it: whether social context is always translatable in terms of ‘geospatial’ location.  Does the concept of ‘place’, for example, really extend to the case of ‘virtual space’ – or does virtual space effectively break free of any geospatial definition?  The question is, of course, very pertinent, given the importance for this population in particular, of dating apps.  Interestingly, Yu & Shang (STIs), in a paper published online, make a case for characterizing an important category of YMSM (occupying a specific ‘place’ in contemporary China society) in terms of extreme geospatial mobility.  One would like to know how B&S would accommodate the paradoxical existence of social ‘places’ defined by the loss of geospatial definition.  Are we still really talking about place?

Location of HIV-2 emergence determined by distribution of indigenous cultural practices of male circumcision

16 Jan, 17 | by Leslie Goode, Blogmaster

Sousa & Vandamme demonstrate a robust correlation between HIV-2 prevalence at the time of the 1980s surveys and the absence of indigenous practices of male circumcision earlier in the century.  This is a complex and interdisciplinary study, involving some of the earliest large-scale, West African serological surveys of HIV-2 (1980s) and extensive ethnography of the region throughout the twentieth century.

HIV-2 seems to have crossed the species barrier into humans from a primate called the ‘sooty mangabey’.  The two epicentres of the 1980s HIV-2 epidemic – south-west Côte I’Ivoire and Guinea Bissau – correspond to the two points along the band of sooty mangabey territory where ethnic groups were to be found who did not practice circumcision (Côte I’Ivoire), or performed it only late in life or very intermittently (Guinea Bissau).  The complexity of this study arises from the fact that, thanks to waves of islamicization, male circumcision has been widely adopted across the region even in areas where it was traditionally prohibited.  Hence investigation of the correlation with HIV-2 emergence, probably in the 1940s, required the authors to go back to ethnographic accounts preceding islamicization.

Of course, the certainty of a causal link cannot be established.  But Sousa & Vandamme discover a strong negative correlation between male circumcision and HIV-2 (Spearman rho = -0.546).  Their results are supported by studies that establish the same negative relationship with HIV-1, both in sub-Saharan Africa (Moses and Plummer) and, more recently in Papua New Guinea (MacLaren & Vallely/STIs).  A likely causative mechanism might be the prevalence of ulcerative sexually transmitted infections (Weiss & Hayes/STIs).

So Sousa & Vandamme offer an additional ‘ecological’ reinforcement of the public health rationale for encouraging voluntary male medical circumcision (VMMC).  Yet what is also interesting, from a public health perspective, is the importance their study attributes to culture in the adoption of a practice like male circumcision.  In the present case, for once, the impact would appear to have been very positive from the medical point of view. The authors speak, for example, of islamicization, along with ethnic intermarriage in the cities, as having given rise to ‘social pressure to be circumcised in order to be accepted by women’, and the ‘abandonment of traditional prohibitions of male circumcision’. Of course, the impact of indigenous culture may often be less benign from a medical point of view – as the source of conservative attitudes that tend to hold back and limit the uptake of VMMC.  As, for example, where males have seen male circumcision as the practice of potentially hostile neighbouring groups (Cultural constraints on uptake of circumcision/STI/blogs), or as a practice uniquely suited to those younger age groups on whom it was traditionally performed (Mbabazi/STIs).  But, either way, it is noteworthy that the influence of local culture would often seem to be so decisive.  So there may be an argument, for electing to promote infant circumcision, as an evidently medical practice that runs less risk of falling foul of prevailing cultural attitudes that restrict ‘demand’ (Gray & Kigozi/STIs; Feasibility of infant circumcision/STIs/blogs).




Prevention of anogenital cancers in women may be an additional benefit of HPV vaccination

14 Oct, 16 | by Leslie Goode, Blogmaster

Cervical cancer is evidently the most important, but by no means the only, health risk that vaccination against HPV aims to avert. The potential impact of vaccination on other cancers (not to mention genital warts) may also be a factor in estimating the cost benefit of achieving higher vaccination coverage, as well as determining priorities for vaccination programmes (e.g. the relative importance of achieving high coverage for males).  Recent studies have investigated the role of HPV in the rising incidence of head and neck – especially oropharyngeal – cancers (Field & Lechner/STIs; King & Sonnenberg/STIs), and in the development of anal cancers amongst MSM (Poynten & Garland/STIs).  The dramatic impact of vaccination programmes on the prevalence of genital warts has already been attested both in Australia, where vaccination was introduced in 2007 (Chow & Fairley/STIs ), and, more recently in the UK (Canvin & Mesher/STIs ).

In addition to these benefits of HPV vaccination, a recent Danish nationwide cohort study (Sand & Kjaer (S&K)) draws attention to another relatively limited, but nevertheless significant, benefit in the shape of a range of anogenital cancers in women – i.e. anal, vaginal and vulvar cancers.  These seem to be strongly associated with the occurrence of high grade cervical intraepithelial neoplasia (CIN2 & 3), and should therefore be numbered amongst the adverse effects of HPV that vaccination may help to prevent.  Given the relative rarity of these cancers (total yearly incidence in UK, both male and female, is currently about a quarter of that of oropharyngeal cancers), an important advantage of S&K’s study is its impressive scale.  It investigates no less than 2.8 million women born 1918-1990 over the period from 1978 to 2012. Also, unlike similar studies, it is able to control not only for age, but for a range of potential confounders such as socio-economic status and smoking.  The use of CIN2/CIN3 as a proxy for HPV infection seems well supported by the evidence (Tachezy & Vonka/STIs; Azwa & Harun (STIs)).

The key findings of the study were as follows.  Relative risk of anal, vulvar and vaginal cancers following CIN2/3 as against no such history was found to be greatly increased: RR 2.8, 2.5, 8.3 after CIN2; 4.1, 3.9, 17.4 after CIN3.  Risk was particularly high in the first year after CIN; but the increased risk persisted, suggesting the effect could not be attributed to surveillance bias.  So, for example, analysis showed increased risks of anal, vulvar and vaginal cancers at ≥25 years after CIN3 diagnosis of RR 4.8, 3.2, and 5.5, respectively.  In non-cervical anogenital cancer, HPV16 was the most frequently detected HPV type.  The fact that cancer risk following CIN3 is substantially greater than it was following CIN2 suggests to the authors that the cause of both may be attributable to an inadequate immune response to HPV in certain women, leading to a failure to clear the infection.  The propensity of persistent HPV to spread to the entire anogenital region explains the range of cancers (anal, vaginal, vulvar) in respect to which these women seem to be at heightened risk (see Simpson & Turner/STIs ).

Global patterns in ante-natal syphilis prevalence: Why is sub-Saharan Africa different?

18 Jul, 16 | by Leslie Goode, Blogmaster

‘Can a meaningful pattern be discerned in the large variations in syphilis rates over the last century?’ This is the question addressed by a recent systematic review – Kenyon & Tsoumanis (K&T) – based on published data on ante-natal syphilis prevalence (ASP) from those countries for which that data is available since at least 1951.   This cutoff reduces the number of countries that qualify for inclusion, but allows more recent trends in the late twentieth, and early twenty-first, centuries, to be set against the background of the impact of the introduction of penicillin in the 1950s. A pattern emerges from the data, which K&T then to seek to explain by investigating its association with various potential variables through multivariate analysis: per capita GDP; circumcision practice; health expenditure; efficacy of diagnosis/treatment; geographical region.

The pattern itself is: in most parts of the world, a more or less steep decline following the introduction of penicillin – ultimately, by the 1990s, to below 1%, and by the 2000s, to below (massively below, in many cases) 0.5%; in sub-Saharan Africa alone, a decline plateauing out at around 6% up until the end of the twentieth century, when there is a further decline to just above 1.5%.  A limitation of the study is its concentration on eleven countries for which ASP data is available from before the days of penicillin, with only two of those countries being in sub-Saharan Africa (South Africa and Zimbabwe).  So far as concerns more recent evidence for ASP prevalence, the kind of rates that the authors give for SA and Zimbabwe seem, broadly, to be replicated in other countries of sub-Saharan Africa (Otieno-Nyunya & Kaiser/STIs (Kenya); Makasa & Sandoy/STIs (Zambia); Kirakoya-Samadoulougou & Nagot/STIs (Burkina-Faso);  Ardu-Sarkodie & Peeling/STIs (Ghana), and their rates for the other regions to be replicated in other non-sub-Saharan African settings (Cheng & Cai/STIs (China); Galdava & Domeika/STIs (Georgia) Thirumoorthy & Lim/STIs (Singapore)).

As for the explanation of this pattern, the authors find no association on multivariate analysis with any of their potential variables, save with residence in sub-Saharan Africa.  This is itself an interesting negative finding, and prompts the authors to consider other population-level correlations also included in the evidence reviewed – notably, with prevalence of HIV and HSV-2; ‘the populations that in the 1990s had high prevalences of syphilis and HSV-2 went on to have high HIV prevalences’.  The correlation with prevalence of HSV-2 is of particular interest because it is unlikely that the prevalence of the one infection could have influenced that of the other (see also: Hochberg & Dandona/STIs).  To K&T, it suggests the likely importance of ‘more connected sexual networks’ and ‘greater partner concurrency’ in explaining traditionally – and currently – high relative ASP levels in sub-Saharan Africa.  However, they refer to studies that contest this hypothesis, and emphasize the need for further research to elucidate the factors underpinning difference in syphilis rates – especially given the possibility that the successful use of ART in those countries may be accompanied by the re-establishment of former sexual networks.

Where next for HIV prevention in New Zealand?

29 Jan, 16 | by Leslie Goode, Blogmaster

A recent issue of the New Zealand Medical Journal (NZMJ) (128: vol. 1426) gives pride of place to a series of papers that reconsider the way forward for HIV prevention in New Zealand (NZ) against the background of the past thirty years.  Recent contributions to STI journal by these authors analyse the behavioural surveillance data from NZ (Saxton & Hughes (STIs); Lachowsky & Summerlee (STIs); Lachowsky & Dewey (STIs)); the papers in NZMJ set these findings against a broader background (Saxton & Giola; Hughes & Saxton; Dickson & Saxton; Saxton & Ludlam).

Broadly speaking, the situation in NZ resembles, both in nature and scale, what we find in Western European countries: namely, persistent but relatively low-level epidemics concentrated in the MSM population (above all, in Auckland), and among heterosexual individuals of foreign extraction (Dickson & Saxton).

The distinctiveness of the NZ epidemics, as against those of Western Europe, lies primarily in geo-political factors: such as migration from sub-Saharan Africa, which reached a peak in 2006 before abruptly declining – or the changing demography of Auckland with its large populations of South Asians and people of Pacific origin (Dickson & Saxton: Lachowsky & Summerlee (STIs)).  The main emphasis of the NZMJ papers, however, is on issues that will have a familiar ring to West European readers – such as the importance of achieving a balance between public health and clinic-based approaches to HIV control.

Overall, their account suggests some considerable degree of success on the part of health interventions – but in the face of a public health challenge that is constantly evolving and may yet prove intractable.  As regards the success, some behavioural surveillance data indicate levels of condom use with casual partners of 85% (Hughes & Saxton; Saxton & Hughes (STIs));  The challenge is represented by the growing minority who do not perceive HIV as a threat on account of new treatments (Hughes & Saxton; Saxton & Ludlam). There also remain, as elsewhere, the problems of high levels of undiagnosed HIV (c. 20%) and relatively late presentation to health services (over a third of MSM at CD4=<350/mm3).  A things stand, the worst kind of scenarios seen amongst gay communities in Thailand or the US would appear to have been averted.  Nevertheless, the epidemics show every sign of persisting, and, given a level of diagnosis that it is marginally higher than seen hitherto, may still turn out to be on an upward trajectory.

A key focus of the NZMJ editorial (Saxton & Giola) is on the continued importance of behaviour-based interventions in a world where the momentum seems to have shifted to clinic based control involving pharmaceuticals.  They highlight the danger that the medicalization of HIV prevention could lead to a disinvestment in behaviour-based interventions, which, they imply, would not be conducive to controlling the epidemic.   In this regard, the authors cite Phillips & Cambiano who argue that a mere 10% reduction in condom use would, without improvements in testing levels and ART initiation, result in a doubling of HIV incidence over 15 years.

The varied nature of the US HIV/AIDS epidemic: what makes the South so different?

27 Feb, 15 | by Leslie Goode, Blogmaster

As of 2011, 38% of all US citizens diagnosed with HIV were from a block of nine states in the south-east, sometimes referred to as “the South”: Louisiana, Alabama, Florida, N. and S. Carolina, Georgia, Texas, Mississippi and Tennessee. Death rates among those living with HIV in this region were, by far, the highest of any US region.  A recent study (Reif & Wilson) uses CDC HIV surveillance data to seek to assign characteristics to the large number of persons in that region diagnosed with, and frequently failing to survive, HIV/AIDS, in order to determine what it is about this region of the US that makes it peculiarly vulnerable to the epidemic.

A number of these characteristics were not specific to the South, but shared by all the southern states: the high proportion of those diagnosed who are female (27%: US average 20.9%), who have contracted HIV through hetero-sexual relations (14.5%: US average 11.7%) and who fall in the 13-24 yr age group. What differentiates the South more particularly, is the considerably higher percentages of diagnoses among those living in rural (11%) and suburban (17%) areas, though even urban rates (29.6 per 100,000) are higher in the South than in other regions.  Five-year survival following AIDS diagnosis, at 73%, is considerably lower than the US average (77%), and lower than for any other region. Survival rates following HIV diagnosis were considerably lower for rural (82%) than for urban (86%) areas.  Above all, the death, rate at 27.3 per 1000, was considerably higher than in any other region of the US. (HIV mortality in the UK fell from 21.8 to 8.2 per 1000 over the years 1997-2008 (Smith & Delpech (STI))).

The high death rates for the South suggest, the authors claim, a fundamental “disconnect” between diagnosis and maintenance of care in the region. Moreover, when the figures are adjusted to take account of characteristics of individuals living with HIV, including sex, race, mode of transmission etc., the disparity remains substantively unchanged or accentuated. This likely indicates underlying structural factors affecting the states of the South.  Obvious candidates would be lower insurance coverage, lower levels of income and education. On the basis of the convergence of high death rates and the high proportion of rural and suburban HIV cases in the region, the authors also evoke, more speculatively, the “class system unique to the US South” which has traditionally allowed little social mobility.  They argue this may have contributed towards a social environment among lower strata characterized by a combination of stigmatization and distrust of medical services, which is very unconducive to retention in care.

Living dangerously in the Dominican Republic and Mexico City: can cash transfer payments be used to counteract the “risk premium”?

17 Dec, 14 | by Leslie Goode, Blogmaster

The Caribbean has the highest levels of HIV outside sub-Saharan Africa – and the Dominican Republic (DR), which together with Haiti accounts for 70% of all people living with HIV in the Caribbean region, is a hotspot.  While there has been a 73% reduction in the rate of new infections in the DR between 2001 and 2011, prevalence of HIV remains high among key populations of MSM (6%) and female sex-workers (3%).  A recent qualitative study has sought to investigate the relations between the drug trade, sex tourism, and risk taking which may hold the secret of the obstinately high-levels of HIV in these key populations (Guillamo-Ramos & Robles).  In-depth interviews, along with drug screening, were conducted with 30 local drug users in Sosua, known for its tourist sex industry.

Three major themes emerge.  First, drugs are freely available as a result of diversion from the major drug routes running from N to S America through the DR.  Second, they have become integral to the local tourist industry – specifically as a vital component of sex work.  Third, the engagement of locals, along with tourists, in commercial sex fuelled by drug use gives rise to the kind high-risk behaviours that sustain the spread of HIV in the local population.

What, from the public health angle, seems particularly challenging in this situation is that the element of risk-taking isn’t merely an incidental effect of the sexual activity; it is precisely the element that makes that activity attractive, and – from the locals’ point of view – lucrative.  Participants associate sex work and drug use with improved livelihood, and describe how risk behaviours are part of the economic negotiating process.

This is the same general kind of problem described in the reported base-line study of a pilot trial of an intervention among male sex workers in Mexico City (STI/Galarraga & Sosa-Rubi).  These male sex-workers are at particular risk of infection because they receive market-based inducements from clients to engage in condomless sex.  It is not simply that MSW are neglecting to take precautions; the average price for a sex transaction is 35% higher for condomless sex – and, given MSW may be unemployed (16%), or dependent for their income on sex work (37%), the economic pressures to engage in unsafe practices are considerable.

The Punto Seguro pilot trial, based at the Clinica Condesa, an HIV centre in Mexico City, is considering as a potential solution the idea of a conditional cash transfer (CCT) whereby MSW are rewarded for keeping themselves free of curable STIs over a six-month period.  Within Mexico CCT has been employed, since the 1990s to provide incentives for poor people to keep their children in school, and to attend preventative check-ups, though not apparently in the sphere of HIV.  In the US, however, it has been used to prevent persistent STIs and pregnancy amongst the Latino population (STI/Minnis & Padian), in Pakistan to encourage infected men to disclose to their wives, and have them tested (STI/Khan & Khan).

The paper sets out the procedures and the baseline data for investigating the effectiveness of a form of this kind of intervention.  The 267 participants have been randomized to four groups: control; medium conditional incentive ($50); high conditional incentive ($75); unconditional incentive ($50). Previous formative work established the incentive levels necessary for behaviour change ($156 per year).  It is also hoped that CCT interventions may benefit participants by helping to link them into care – since of the participants in the trial who knew they were infected with HIV, only 40% were on treated, and of these, only 61% had achieved viral suppression.

Tracking the origin, early spread, and ignition of pandemic #HIV-1 through new approaches to phylogenetic analysis

17 Nov, 14 | by Leslie Goode, Blogmaster

“Distribution of HIV-1 subtypes in a population”, state Mumtaz & Raddad (STI) in a study of the HIV pandemic in the Middle East, “tracks the spread and evolution of the epidemic”.  Various studies covered in our previous blogs have attempted to read the history of the progress of the HIV epidemic through the evidence of the distribution of HIV genetic sub-types: Tatem & Salemi (STI/blogs) have investigated its spread throughout Africa; Zhao & Roca (STI/blogs) pass beyond the human epidemic to consider the genetic evidence for repeated transmission from chimpanzees to humans.

Now Faria & Lemey (F&L), in a paper recently appearing in Science, offer an account of the critical early phase of limited spread within Central Africa and the ignition of pandemic HIV-1 around 1960, bringing statistical approaches to bear to HIV-1 sequence data.  F&L produce a time-scaled phylogenetic “tree” of HIV-1 group M lineages, matching these up in each case with the geographical location of their earliest manifestation.

This approach points to the very strong likelihood (PP = 0.99) of an origin of the HIV1 epidemic in Kinshasa around 1920. Study of lineage migration shows comparatively early spread from Kinshasa to Brazzaville (Republic of Congo (RC)), and Mbuji-Mayi and Lubumbashi (southern Democratic Republic of Congo (DRC)) along the railway network, and its arrival around a decade later in Bwamanda and Kisangani (northern DRC).  The crucial period around 1960 (1952-1968) sees, for group M HIV-1, an exponential growth in levels of M-group transmission, while growth in group O transmission remains at previous levels.

But the most interesting aspect of the study relates to conditions around the sudden surge in group M HIV-1 transmission, as indicated by the accelerated ramification of viral lineages during the crucial period.  The authors consider the hypothesis that associates this ramification with the geographic dispersal of the epidemic, with the lineages emerging in the more widely distributed populations now being infected.  They reject this hypothesis, however, on the grounds that, when the epidemic history of lineages maintaining ancestry within Kinshasa is constructed, these turn out to exhibit phylo-genetic characteristics that are comparable to those of lineages in central Africa.

They conclude that the crucial explosion of pandemic HIV-1 transmission probably occurred in Kinshasa as a result of a historic contingency affecting a particular population subgroup.  Prime contenders are iatrogenic transmission as a result of the administration of unsterilized injections at STI clinics, and/or post-independence changes in sexual behaviour e.g. among commercial sex-workers.  The authors find support for the iatrogenic hypothesis in a study of the hepatitis C virus in the DRC which shows that it exhibits an age cohort effect, and in reports of an epidemic of hepatitis B in Kinshasa around 1951-2.

“Hispanic” label masks the specificity of the Puerto Rican #HIV problem in US Northeast

12 Nov, 14 | by Leslie Goode, Blogmaster

Interventions for HIV prevention should be informed by an understanding of the long-term source of infection, and not just by recent distribution (Mishra & Boily (STIs)).  Amongst recent studies that have sought to inform future interventions are investigations of known subgroups thought to be a potential bridge into the wider population – such as migrant workers, or sex workers (STI/Kissinger & Shedlin; STI/Faisel & Cleland).  There are other investigations that seek to refine on the definition of such groups (STIs/Davies & Tucker; STIs/Bayer & Coates).  But could there be instances where classifications established for the purposes of data collection actually mask the existence of the groups that could have epidemiological importance?

Puerto Ricans in the north-east of the US may be an interesting case in point.  A recent article (Deren & Santiago-Negron(D&S)) claims that the classification “Hispanic”, generally applied to Puerto Ricans for the purpose of data collection, may have obfuscated the distinctiveness of a Puerto Rican subgroup with its own specific risk profile, and considerable unmet medical health needs.   As though to illustrate the point, D&S assemble various data relating to strong correlations, for example: between AIDS diagnosis and being Hispanic; between residence in the North East of the US and IDU-associated HIV; between HIV incidence and being a Hispanic IDU.  Cumulatively – and taken along with the concentration of Puerto Ricans in the NE, and what is known of the high incidence of IDU-associated HIV in Puerto Rico itself – these data indicate the probability of a strong association, at least for the US North Eastern states, between Puerto Rican Hispanic identity and a high risk of drug-derived or heterosexually-transmitted HIV.  Furthermore, it is not only the subgroup of US Porto Ricans that have tended to slip under the net, according to D & J; high levels of IDU-transmitted HIV in the island of Puerto Rico itself have failed to attract due attention, on account of the peculiar status of Puerto Rico – which is a US territory, without being a US state.  As a result, Puerto Rico tends to figure neither in statistics for the Caribbean (as a US territory), nor in statistics for the US (since it is not a US state).

For Puerto Ricans – with an AIDS fatality at six times the US average and rates of new IDU and heterosexual infection twice that of the US – the problems of their anomalous status do not end with inadequate reporting.   Budgets for syringe exchange programs (SEPs) are only a fifth of what they are in the US Northeast, while Puerto Rican IDUs are only a fifth as likely to be in treatment.  SEP schemes cannot be funded by the US federal government, while the local Puerto Rican response to the drugs problem has, until recently, been largely provided through faith-based programs, with addiction defined by the Mental Health Law (2000) as a spiritual and social problem rather than a mental disorder.  Relocation to the US Northeast for drug treatment has become a commonly recommended option, with 85% of Puerto Rican admission to drug treatment taking place in the US Northeast.

In view of all this, D&S recommend partnership between federal, local and private entities to develop a cross-regional approach to the Puerto-Rican epidemic.  They also point out the challenges posed for such an approach by the unique status of Puerto Rico as a territory, without the full representation available to states in the Northeast.

How does neighbourhood impact on STI (Chlamydia) risk?

19 Jun, 13 | by Leslie Goode, Blogmaster

The influence of neighbourhood on STI (and more particularly Chlamydia) acquisition is widely recognized fact.  Biello & Nikkolai argue for UK urban populations that neighbourhood socio-economic status (SES) is more closely correlated with Chlamydia risk than individual SES (  In another UK study (Birmingham), Shahmanesh & Ross find residence in neighbourhoods having certain SES characteristics to be  strongly predictive of both Chlamydia and Gonorrhoea (

But what is it exactly about these neighbourhoods that places their residents at far greater risk of STI acquisition than other neighbourhoods?  Is it, as some sociologists have proposed, the general level of social disorganization that heightens the risk, or is it poverty itself, or maybe the degree of residential instability?  Ford & Browning, in a recent study using data on a sample of 11,460 young adults from the US National Longitudinal Study of Adolescent Health, waves 1 and 3 (1994-2002), attempt to establish the pathway whereby neighbourhood influences the risk of acquiring Chlamydia (

The nature of the data allows the researchers to capture the association of Chlamydia acquisition amongst young people in their twenties, not only to various characteristics of their current neighbourhoods (i.e. at wave 3 of the study), but also the characteristics of those neighbourhoods in which they accomplished their transition into adulthood some years before (i.e. at wave 1).  The main finding of Ford & Browning is that characteristics of the current neighbourhood show no statistically significant correlation with Chlamydia acquisition, but characteristics of neighbourhoods at the time of adolescence – especially  “poverty” (on different models OR 1.23 & 1.25 respectively) – do show a correlation.  The obvious explanation is that these associations are mediated through individual variables such as sexual behaviour or psychological factors (e.g. depression).  Yet multi-variate findingsdid not confirm this mediation.

So what potential mechanisms are there for the influence of neighbourhood on STI acquisition?  While stressing the need for further research, the authors point principally to two.  The first of these is a “network” explanation.  Maybe neighbourhood of residence during adolescence could influence opportunities for future partner selection;  young adults who lived in an impoverished neighbourhood during adolescence may have a pool of higher risk sexual partners to choose from compared to their peers from more advantaged neighbourhoods.  The other interesting possibility is the influence of chronic stress associated with adverse neighbourhood conditions resulting in impaired immune system function and increased infectious disease risk through increased inflammation and cortisol secretion.

Either way, structural factors that are largely refractory even to the most ambitious public health interventions.  I am reminded of Wilkinson and Picket’s argument in The Spirit Level ( the determinants of health outcomes are effectively located at a level that is presumably beyond of the reach of any but the most radical (indeed revolutionary) political interventions.  “The poor you will always with you.”  At the same time, sociological explanations of this kind provide justification for careful targeting of public health resources on needy populations and help us counter the “inverse care” law.


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