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  1. 1
    Peer Reviewed

    Prediction of community prevalence of human onchocerciasis in the Amazonian onchocerciasis focus: Bayesian approach. [Prévisions portant sur la prévalence communautaire de l'onchocercose humaine au niveau du foyer amazonien de l'onchocercose : approche bayésienne]

    Carabin H; Escalona M; Marshall C; Vivas-Martinez S; Botto C

    Bulletin of the World Health Organization. 2003 Jul; 81(7):482-490.

    Objective: To develop a Bayesian hierarchical model for human onchocerciasis with which to explore the factors that influence prevalence of microfilariae in the Amazonian focus of onchocerciasis and predict the probability of any community being at least mesoendemic (>20% prevalence of microfilariae), and thus in need of priority ivermectin treatment. Methods: Models were developed with data from 732 individuals aged515 years who lived in 29 Yanomami communities along four rivers of the south Venezuelan Orinoco basin. The models’ abilities to predict prevalences of microfilariae in communities were compared. The deviance information criterion, Bayesian P-values, and residual values were used to select the best model with an approximate cross-validation procedure. Findings: A three-level model that acknowledged clustering of infection within communities performed best, with host age and sex included at the individual level, a river-dependent altitude effect at the community level, and additional clustering of communities along rivers. This model correctly classified 25/29 (86%) villages with respect to their need for priority ivermectin treatment. Conclusion: Bayesian methods are a flexible and useful approach for public health research and control planning. Our model acknowledges the clustering of infection within communities, allows investigation of links between individual- or community-specific characteristics and infection, incorporates additional uncertainty due to missing covariate data, and informs policy decisions by predicting the probability that a new community is at least mesoendemic. (author's)
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  2. 2

    Hepatitis B in St Petersburg, Russia (1994-1999): incidence, prevalence and force of infection.

    Beutels P; Shkedy Z; Mukomolov S; Aerts M; Shargorodskaya E

    Journal of Viral Hepatitis. 2003 Mar; 10(2):141-149.

    Hepatitis B (HB) is thought to be an expanding health problem in Russia. The incidence of infection was estimated from mandatorily reported HB cases in St Petersburg. The two-sided t-test for independent samples and the LOESS (locally-weighted regression) smoother were used to compare the age at infection for symptomatic, asymptomatic and chronic infections, by gender. The force of infection was estimated from seroprevalence data (907 sera taken in 1999) using a newly developed nonparametric method based on local polynomials, as well as an earlier method based on isotonic regression and kernel smoothers. With the local polynomial method, pointwise confidence intervals (95%) were constructed by bootstrapping. On average, men contracted HB infection at a significantly younger age than women (in 1999, 21.8 vs 22.7 years, respectively). The overall male to female ratio was 1.92. In 1999 the overall incidence almost doubled compared with the preceding years and tripled among the age groups with highest incidence (15–29-year olds: 85% of cases in 1999). The incidence increase was associated with a lower average age at infection (24.1 years in 1994 vs 22.1 years in 1999). The age and gender-specific force of infection estimates generally confirmed the incidence estimates and emphasized the usefulness of local polynomials to do this. Hence HB transmission in St Petersburg occurs mainly in young adults. The dramatic increase of infections in 1999 was probably due to injecting drug use. Without intervention, HB virus is expected to continue to spread rapidly with a greater proportion of female infections caused by sexual transmission. These trends may also provide an indication for HIV transmission. (author's)
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  3. 3

    Combined oral contraceptives, smoking, and cardiovascular risk.

    Farley TM; Meirik O; Chang CL; Poulter NR


    The World Health Organization (WHO) Collaborative Study of Cardiovascular Disease and Steroid Hormone Contraception has quantified the risks of idiopathic venous thromboembolism (VTE), ischemic and hemorrhagic stroke, and acute myocardial infarction (AMI) associated with use of combined oral contraceptives (OCs). The present case-control study estimated the age-specific incidence and mortality of these four diseases among women with no cardiovascular risk factors and modelled the risks attributable to OC use, smoking, and the interaction of the two. Data sources included relative risk estimates from the WHO study and observed incidence rates obtained from hospitals in UK's Oxford region in 1989-93. The increased risk of VTE associated with OC use among nonsmokers contributed over 90% of all cardiovascular events among women 20-24 years and more than 60% in those 40-44 years. Among OC users who smoked, hemorrhagic stroke and AMI accounted for 80% of cardiovascular deaths in the 20-24 year group and 97% among those 40-44 years. Cardiovascular mortality associated with smoking exceeded that associated with OC use at all ages. Attributable risk associated with OC use was 1 death/year/370,000 users aged 20-24 years, 1/170,000 users aged 30-34 years, and 1/37,000 users aged 40-44 years. Among smokers, annual cardiovascular mortality attributable to OC use was estimated at about 1/100,000 users among women under 35 years old and 1/10,000 users among those 35 years of age and older. Among healthy women 35 years and older, the additional mortality associated with OC use is 1.4/100,000/year compared with 5.4/100,000 among smokers and 14/100,000 women who both use OCs and smoke. Any potential reduction in AMI or stroke risk associated with third-generation OCs would be a more important consideration in older women, especially smokers. However, the mortality associated with smoking is far greater than that associated with use of all types of OCs at all ages.
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  4. 4

    New data on oral contraceptive pills and the risk of heart attack. Press release.

    World Health Organization [WHO]

    [Geneva, Switzerland], WHO, 1997 Apr 24. 3 p. (Press Release WHO/33)

    A study conducted by the UNDP/UNFPA/WHO/World Bank Special Program of Research, Development, and Research Training in Human Reproduction confirmed that young women in both developed and developing countries with no predisposing risk factors for cardiovascular disease can use oral contraceptives (OCs) without increasing their risk of acute myocardial infarction. The study was conducted in 21 centers in 12 developing and 7 developed countries and involved 369 women with acute myocardial infarction and 941 healthy controls. The duration of OC use did not affect the risk of heart attack. In OC users under 35 years who smoke and use the pill, the incidence of heart attack increases from the 3.5 cases/million woman-years recorded in nonsmoking OC users to about 40 cases/million woman-years. The risk of heart attack rises substantially, however, in OC users over 35 years of age who smoke: to 500 cases/million woman-years. The overall risk of heart attack is 10 times higher in OC users with high blood pressure than in women with normal blood pressure or non-users of OCs. The data did not reveal consistent differences in heart attack risk according to the OC's estrogen dose; there were too few OC users enrolled in the study who were using pills containing gestodene or desogestrel to permit conclusions about the relative safety of second- and third-generation OCs. These findings indicate that the minimal heart attack risk associated with OC use can be avoided by screening women for potential risk factors for such disease, especially high blood pressure, diabetes, and smoking.
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  5. 5
    Peer Reviewed

    PID risk for IUD users highest in first 20 days after insertion; risk then falls sharply and remains low.

    Turner R

    Family Planning Perspectives. 1992 Sep-Oct; 24(5):235-6.

    Researchers analyzed data on 22,908 women obtained from randomized WHO studies from 23 countries to determine whether the IUD increases the risk of pelvic inflammatory disease (PID). 35% of the women used the TCu220C IUD, 39% other copper releasing IUDs, 16% a hormonal IUD, and 9% the Lippes Loop. The overall PID incidence rate was 0.4% of all IUD insertions or 1.6 cases/1000 woman years. The incidence was greatest during the 1st 20 days after insertion (9.7 cases/1000 women years) and then declined to 1.4/1000 woman years. In fact, the risk of PID was >6 times greater within 20 days after insertion than it was >20 days after insertion. This high risk immediately after insertion was evident in every region where PID existed, at all insertion times, and in all age groups. The higher risk within the 20 days after insertion was attributed to contamination of the uterus during insertion. Women who had an IUD inserted after 1980 experienced PID 50% less often than those who had had it inserted earlier, e.g., the rate ratio for 1977-80 was 1.5 but was 0.5 for 1981-83 and 0.34 for 1984 and after. This may have been due to physicians being more aware of contraindications for IUD use, particularly past infection with sexually transmitted diseases )STDs). The rate ratio was higher in Africa (2.6) than it was in Europe (1) but lower in Asia (0.46) and in the Americas (0.39). None of the subjects in China experienced PID. Older women were at lower risk of PID than 15-24 year olds (0.44 for 25-29 year olds, 0.38 for 30-34 year olds, and 0.35 for =or> 35 year olds). The researchers believed the higher risk life styles of the younger group accounted for this difference. Risk of PID decreased with family size (2.5 for 0 children, 0.56 for 2 children, and 0.39 for at least 4 children). The risk of PID did not differ with IUD type. The researchers concluded that the major determinant of PID is exposure to an STD rather than type of IUD.
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