Withdrawal, "serosorting" and "strategic positioning": use of risk reduction strategies with casual sex partners in men who have sex with men (MSM) in Switzerland, 2007

Introduction: 1) Withdrawal before ejaculation, "serosorting" (to choose a partner of same serostatus) and "strategic positioning" (only insertive vs. only receptive role in anal sex according to serostatus) are known to be used by MSM as alternatives to condom use. 2) Despite their questionable levels of effectiveness they are collectively labelled as "risk reduction strategies" (RRS). Objectives: The aim of this study is to estimate the prevalence and factors related to RRS in men who report unprotected anal intercourse (UAI) with occasional partners in the last 12 months. Methods: 1) In 2007, a module on RRS was included in a repeated national survey conducted among readers of gay newspapers, members of gay organizations and visitors of gay websites (N=2953). 2) Using an anonymous self-completed questionnaire, participants were asked whether, with the aim of avoiding HIV infection, RRS were used with occasional partners. Analysis: 1) Prevalences were calculated in participants who reported UAI with occasional partners in the last 12 months (n=416). 2) A logistic regression was performed, using "at least one RRS" as dependent variable. Number of partners in the last 12 months, HIV-status and usual socio-demographic characteristics were used as independent factors. Result : 1) 70% (292/416) of the participants reporting UAI used at least one RRS when they had unprotected sex with casual partners in the last 12 months (Table 1). 2) Withrawal before ejaculation was the most frequently reported strategy, followed by serosorting and strategic positioning (Table 1). 3) Participants who reported at least one RRS were more likely to be over 30 years and to belong to a gay organisation. HIV-positive and non-tested participants were less likely to report RRS than HIV-negative participants (Table 2). Conclusions: 1) The majority of MSM who reported UAI in the last 12 months tried to reduce risk of HIV transmission by using specific strategies (withdrawal, serosorting, strategic positioning). It is not known, however, to what extent the use of these strategies was systematic. 2) It is necessary to provide MSM with balanced information on these strategies and their respective level of effectiveness. 3) It is important to monitor the use of RRS in HIV behavioural surveillance surveys in MSM.

Preference intensities and risk aversion in school choice: a laboratory experiment

We experimentally investigate in the laboratory two prominent mechanisms that are employed in school choice programs to assign students to public schools. We study how individual behavior is influenced by preference intensities and risk aversion. Our main results show that (a) the Gale-Shapley mechanism is more robust to changes in cardinal preferences than the Boston mechanism independently of whether individuals can submit a complete or only a restricted ranking of the schools and (b) subjects with a higher degree of risk aversion are more likely to play "safer" strategies under the Gale-Shapley but not under the Boston mechanism. Both results have important implications for the efficiency and the stability of the mechanisms.

Investor protection and income inequality: risk sharing vs risk taking

This paper studies the relationship between investor protection, entrepreneurial risk taking and income inequality. In the presence of market frictions, better protection makes investors more willing to take on entrepreneurial risk when lending to firms, thereby improving the degree of risk sharing between financiers and entrepreneurs. On the other hand, by increasing risk sharing, investor protection also induces more firms to undertake risky projects. By increasing entrepreneurial risk taking, it raises income dispersion. By reducing the risk faced by entrepreneurs, it reduces income volatility. As a result, investor protection raises income inequality to the extent that it fosters risk taking, while it reduces it for a given level of risk taking. Empirical evidence from a panel of forty-five countries spanning the period 1976-2000 supports the predictions of the model.

Brain structure in asymptomatic FMR1 premutation carriers at risk for fragile X-associated tremor/ataxia syndrome.

Fragile X-associated tremor/ataxia syndrome (FXTAS), a late-onset movement disorder affecting FMR1 premutation carriers, is associated with cerebral and cerebellar lesions. The aim of this study was to test whether computational anatomy can detect similar patterns in asymptomatic FMR1 premutation carriers (mean age 46.7 years) with qualitatively normal -appearing grey and white matter on brain MRI. We used a multimodal imaging protocol to characterize brain anatomy by automated assessment of gray matter volume and white matter properties. Structural changes in the hippocampus and in the cerebellar motor network with decreased gray matter volume in lobule VI and white matter alterations of the corresponding afferent projections through the middle cerebellar peduncles are demonstrated. Diffuse subcortical white matter changes in both hemispheres, without corresponding gray matter alterations, are only identified through age × group interactions. We interpret the hippocampal fimbria and cerebellar changes as early alterations with a possible neurodevelopmental origin. In contrast, progression of the diffuse cerebral hemispheric white matter changes suggests a neurodegenerative process, leading to late-onset lesions, which may mark the imminent onset of FXTAS.

Sentinel lymph node involvement and a high Breslow index are independent factors of risk for early relapse of melanoma.

AIM: The clinical relevance of sentinel lymph node (SLN) analysis was evaluated prospectively and compared with other known risk factors of relapse in early stage melanoma. METHODS: Surgery was guided by lymphoscintigraphy, blue dye and gamma probe detection. SLN were analysed by haematoxylin eosin (HE) histochemistry and multimarker immunohistochemistry (IHC). Disease free survival (DFS) was evaluated with Kaplan-Meier plots according to different parameters and Cox analyses of variance. RESULTS: From 210 patients a total of 381 SLN were excised. Lymphoscintigraphy identified all excised SLN with only 2 false positive lymphatic lakes. Fifty patients (24%) had tumour positive SLN. With a mean follow-up of 31.3 months, 29 tumour recurrences were observed, 19 (38%) in 50 SLN positive and 10 (6%) in 160 SLN negative patients. Strong predictive factors for early relapse (p < 0.0005) were SLN positivity and a high Breslow index. CONCLUSION: SLN tumour positivity is an independent factor of high risk for early relapse with a higher power of discrimination than the Breslow index.