Harms of cervical cancer screening in the United States and the Netherlands.

We studied harms related to cervical cancer screening and management of screen-positive women in the United States (US) and the Netherlands. We utilized data from four US integrated health care systems (SEARCH), the US National Health Interview Survey, New Mexico state, the Netherlands national histopathology registry, and included studies on adverse health effects of cervical screening. We compared the number of Papanicolaou (Pap) smear tests, abnormal test results, punch biopsies, treatments, health problems (anxiety, pain, bleeding and discharge) and preterm births associated with excisional treatments. Results were age-standardized to the 2007 US population. Based on SEARCH, an estimated 36 million Pap tests were performed in 2007 for 91 million US women aged 21-65 years, leading to 2.3 million abnormal Pap tests, 1.5 million punch biopsies, 0.3 million treatments for precancerous lesions, 5 thousand preterm births and over 8 million health problems. Under the Netherlands screening practice, fewer Pap tests (58%), abnormal test results (64%), punch biopsies (75%), treatment procedures (40%), preterm births (60%) and health problems (63%) would have occurred. The SEARCH data did not differ much from other US data for 2007 or from more recent data up to 2013. Thus compared to the less intensive screening practice in the Netherlands, US practice of cervical cancer screening may have resulted in two- to threefold higher harms, while the effects on cervical cancer incidence and mortality are similar. The results are also of high relevance in making recommendations for HPV screening. Systematic collection of harms data is needed for monitoring and for better incorporation of harms in making screening recommendations.

Elimination of African onchocerciasis: modeling the impact of increasing the frequency of ivermectin mass treatment.

The African Programme for Onchocerciasis Control (APOC) is currently shifting its focus from morbidity control to elimination of infection. To enhance the likelihood of elimination and speed up its achievement, programs may consider to increase the frequency of ivermectin mass treatment from annual to 6-monthly or even higher. In a computer simulation study, we examined the potential impact of increasing the mass treatment frequency for different settings. With the ONCHOSIM model, we simulated 92,610 scenarios pertaining to different assumptions about transmission conditions, history of mass treatment, the future mass treatment strategy, and ivermectin efficacy. Simulation results were used to determine the minimum remaining program duration and number of treatment rounds required to achieve 99% probability of elimination. Doubling the frequency of treatment from yearly to 6-monthly or 3-monthly was predicted to reduce remaining program duration by about 40% or 60%, respectively. These reductions come at a cost of additional treatment rounds, especially in case of 3-monthly mass treatment. Also, aforementioned reductions are highly dependent on maintained coverage, and could be completely nullified if coverage of mass treatment were to fall in the future. In low coverage settings, increasing treatment coverage is almost just as effective as increasing treatment frequency. We conclude that 6-monthly mass treatment may only be worth the effort in situations where annual treatment is expected to take a long time to achieve elimination in spite of good treatment coverage, e.g. because of unfavorable transmission conditions or because mass treatment started recently.

Too old to have children? Lessons from natural fertility populations.

STUDY QUESTION: Is it possible to construct an age curve denoting the ages above which women are biologically too old to reproduce? SUMMARY ANSWER: We constructed a curve based on the distribution of female age at last birth in natural fertility populations reflecting the ages above which women have become biologically too old to have children. WHAT IS KNOWN ALREADY: The median age at last birth (ALB) for females is ∼40-41 years of age across a range of natural fertility populations. This suggests that there is a fairly universal pattern of age-related fertility decline. However, little is known about the distribution of female ALB and in the present era of modern birth control, it is impossible to assess the age-specific distribution of ALB. Reliable information is lacking that could benefit couples who envisage delaying childbearing. STUDY DESIGN, SIZE, DURATION: This study is a review of high-quality historical data sets of natural fertility populations in which the distributions of female age at last birth were analysed. The studies selected used a retrospective cohort design where women were followed as they age through their reproductive years. PARTICIPANTS/MATERIALS, SETTING, METHODS: Using a common set of eligibility criteria, large data files of natural fertility populations were prepared such that the analysis could be performed in parallel across all populations. Data on the ALB and confounding variables are presented as box and whisker plots denoting the 5th, 25th, 50th, 75th and 95th percentile distribution of the age at last birth for each population. The analysis includes the estimation of Kaplan-Meier curves for age at last birth of each population. The hazard curve for ALB was obtained by plotting the smoothed hazard curve of each population and taking the lowest hazard within a time period of at least 5 years. This lowest hazard curve was then transformed into a cumulative distribution function representing the composite curve of the end of biological fertility. This curve was based on the data from three of the six populations, having the lowest hazards of end of fertility. MAIN RESULTS AND THE ROLE OF CHANCE: We selected six natural fertility populations comprising 58 051 eligible women. While these populations represent different historical time periods, the distribution of the ages at last birth is remarkably similar. The curve denoting the end of fertility indicates that <3% of women had their last birth at age 20 years meaning that almost 98% were able to have at least one child thereafter. The cumulative curve for the end of fertility slowly increases from 4.5% at age 25 years, 7% at age 30 years, 12% at age 35 years and 20% at age 38 years. Thereafter, it rises rapidly to about 50% at age 41, almost 90% at age 45 years and approaching 100% at age 50 years. LIMITATIONS, REASONS FOR CAUTION: It may be argued that these historical fertility data do not apply to the present time; however, the age-dependent decline in fertility is similar to current populations and is consistent with the pattern seen in women treated by donor insemination. Furthermore, for reproductive ageing, we note that it is unlikely that such a conserved biological process with a high degree of heritability would have changed significantly within a century or two. WIDER IMPLICATIONS OF THE FINDINGS: We argue that the age-specific ALB curve can be used to counsel couples who envisage having children in the future. Our findings challenge the unsubstantiated pessimism regarding the possibility of natural conception after age 35 years. STUDY FUNDING/COMPETING INTEREST(S): No external funding was either sought or obtained for this study. There are no conflicts of interest to be declared.

African Programme For Onchocerciasis Control 1995-2015: model-estimated health impact and cost.

BACKGROUND: Onchocerciasis causes a considerable disease burden in Africa, mainly through skin and eye disease. Since 1995, the African Programme for Onchocerciasis Control (APOC) has coordinated annual mass treatment with ivermectin in 16 countries. In this study, we estimate the health impact of APOC and the associated costs from a program perspective up to 2010 and provide expected trends up to 2015. METHODS AND FINDINGS: With data on pre-control prevalence of infection and population coverage of mass treatment, we simulated trends in infection, blindness, visual impairment, and severe itch using the micro-simulation model ONCHOSIM, and estimated disability-adjusted life years (DALYs) lost due to onchocerciasis. We assessed financial costs for APOC, beneficiary governments, and non-governmental development organizations, excluding cost of donated drugs. We estimated that between 1995 and 2010, mass treatment with ivermectin averted 8.2 million DALYs due to onchocerciasis in APOC areas, at a nominal cost of about US$257 million. We expect that APOC will avert another 9.2 million DALYs between 2011 and 2015, at a nominal cost of US$221 million. CONCLUSIONS: Our simulations suggest that APOC has had a remarkable impact on population health in Africa between 1995 and 2010. This health impact is predicted to double during the subsequent five years of the program, through to 2015. APOC is a highly cost-effective public health program. Given the anticipated elimination of onchocerciasis from some APOC areas, we expect even more health gains and a more favorable cost-effectiveness of mass treatment with ivermectin in the near future.

Risk of cervical cancer after completed post-treatment follow-up of cervical intraepithelial neoplasia: population based cohort study.

OBJECTIVE: To compare the risk of cervical cancer in women with histologically confirmed cervical intraepithelial neoplasia who returned to routine screening after having completed post-treatment follow-up with consecutive normal smear test results with women with a normal primary smear test result. DESIGN: Population based cohort study using data from a nationwide pathology register. SETTING: The Netherlands, 1994 to 2006. POPULATION: 38,956 women with histologically confirmed intraepithelial neoplasia grades 1 to 3 with completed follow-up after treatment. INTERVENTION: Routine post-treatment follow-up of cervical intraepithelial neoplasia, recommending smear tests at six, 12, and 24 months. MAIN OUTCOME MEASURE: Incidence of cervical cancer in the period from completed follow-up with negative test results after cervical intraepithelial neoplasia to the next primary test. 10-year hazard ratios were compared with periods after normal results for the primary smear test, adjusted for year in follow-up. RESULTS: 20 cervical cancers were diagnosed during 56,956 woman years after completed follow-up of cervical intraepithelial neoplasia, whereas 1613 cervical cancers were diagnosed during 25,020,697 woman years after a normal primary smear test result. The incidence of 35.1 (95% confidence interval 21.4 to 54.2) per 100,000 woman years and 6.4 (6.1 to 6.8) per 100,000 woman years, respectively, led to an adjusted hazard ratio of 4.2 (95% confidence interval 2.7 to 6.5) for periods after completed follow-up compared with periods after normal primary smear test results. This hazard ratio was increased for all ages. No significant difference in risk of cervical cancer was observed by grade of cervical intraepithelial neoplasia. CONCLUSIONS: An excess risk of cervical cancer previously observed for women treated for cervical intraepithelial neoplasia was also observed in the subgroup of women who completed their post-treatment follow-up with three consecutive normal smear test results. The overall corrected risk of cervical cancer in these women was increased fourfold 35 cases per 100,000 woman years) compared with women with normal primary smear test results (6 per 100,000 woman years).

Cervical cancer screening in the United States and the Netherlands: a tale of two countries.

CONTEXT: This article compares cervical cancer screening intensity and cervical cancer mortality trends in the United States and the Netherlands to illustrate the potential of cross-national comparative studies. We discuss the lessons that can be learned from the comparison as well as the challenges in each country to effective and efficient screening. METHODS: We used nationally representative data sources in the United States and the Netherlands to estimate the number of Pap smears and the cervical cancer mortality rate since 1950. The following questions are addressed: How do differences in intensity of Pap smear use between the countries translate into differences in mortality trends? Can population coverage rates (the proportion of eligible women who had a Pap smear within a specified period) explain the mortality trends better than the total intensity of Pap smear use? FINDINGS: Even though three to four times more Pap smears per woman were conducted in the United States than in the Netherlands over a period of three decades, the two countries' mortality trends were quite similar. The five-year coverage rates for women aged thirty to sixty-four were quite comparable at 80 to 90 percent. Because screening in the Netherlands was limited to ages thirty to sixty, screening rates for women under thirty and over sixty were much higher in the United States. These differences had consequences for age-specific mortality trends. The relatively good coverage rate in the Netherlands can be traced back to a nationwide invitation system based on municipal population registries. While both countries followed a "policy cycle" involving evidence review, surveillance of screening practices and outcomes, clinical guidelines, and reimbursement policies, the components of this cycle were more systematically linked and implemented nationwide in the Netherlands than in the United States. To a large extent, this was facilitated by a public health model of screening in the Netherlands, rather than a medical services model. CONCLUSIONS: Cross-country studies like ours are natural experiments that can produce insights not easily obtained from other types of study. The cervical cancer screening system in the Netherlands seems to have been as effective as the U.S. system but used much less screening. Adequate coverage of the female population at risk seems to be of central importance.

The effect of postponement of first motherhood on permanent involuntary childlessness and total fertility rate in six European countries since the 1970s.

BACKGROUND: Postponement of childbearing since the 1970s has led to an increase in permanent involuntarily childlessness. We will address the magnitude of this trend, the effect of IVF/ICSI and the effect on total fertility rate (TFR an often used demographic measure for the level of fertility) in six EU countries. METHODS: Using a fertility micro-simulation model, we estimate the effect of postponement of first motherhood on permanent involuntary childlessness in six representative European countries since 1970/1985: Sweden, Austria, Czech Republic, The Netherlands, West Germany and Spain. To estimate the effect of IVF/ICSI on this trend, we use data on the results of all IVF/ICSI cycles performed in The Netherlands in 2003 and 2004. RESULTS: Permanent involuntary childlessness approximately doubled since 1970s and rose to ~4% in the Czech Republic and to ~7% in Spain with the other countries in between. If all couples entitled to have IVF/ICSI were to be treated, the effect of postponement would almost have been neutralized. However, only a limited proportion of eligible couple are being treated. Without postponement, TFRs would have been between 0.03 and 0.05 higher. CONCLUSIONS: The effect of postponement on permanent involuntary childlessness is considerable. So far IVF/ICSI only had a slight effect on this trend. The impact of postponement on TFRs is small compared with other demographic trends.

Uptake of faecal immunochemical test screening among nonparticipants in a flexible sigmoidoscopy screening programme.

Screening programmes based on single modality testing may prevent individuals with a preference for a different test from participating. We conducted a population-based trial to determine whether nonparticipants in flexible sigmoidoscopy (FS) screening were willing to attend faecal immunochemical test (FIT) screening. In total, 8,407 subjects were invited in a primary FS screening programme. Invitees did not know at the time of FS invitation that nonparticipants would be offered FIT screening. A total of 4,407 nonparticipants of FS screening were invited for FIT screening (cut-off 50 ng haemoglobin/ml). The participation rate to FS screening was 31% [95% confidence interval (CI): 30-32%]. Among the FS nonparticipants 25% (CI: 24-26%) did attended FIT screening. The participation rate of the two-stage recruitment for FS and FIT screening was 45% (CI: 44-46%). FIT screenees were older (p = 0.02), more often women (p < 0.001) and had a lower social economic status (p = 0.01) than FS screenees. The detection rate (DR) for advanced adenoma was 3.5% (CI: 2.5-4.8%), and for colorectal cancer (CRC) it was 0.3% (CI: 0.1-0.8%) among participants to FIT screening. The DR of the two-stage recruitment was 6.1% (n = 202) for an advanced adenoma and 0.5% (n = 16) for a CRC. In conclusion, offering FIT screening to nonparticipants in a FS screening programme increases the overall participation rate considerably, as a quarter of nonparticipants of FS screening was willing to attend FIT screening. The participation rate remains lower for primary FIT screening in the same population (62%). Women in the target population were more likely to refuse FS than FIT screening. Countries introducing FS screening should be aware of these preferences.

Diagnostic yield improves with collection of 2 samples in fecal immunochemical test screening without affecting attendance.

BACKGROUND & AIMS: The fecal immunochemical test (FIT) is superior to the guaiac-based fecal occult blood test in detecting neoplasia. There are not much data on the optimal number of FITs to perform. We conducted a population-based trial to determine attendance and diagnostic yield of 1- and 2-sample FIT screening. METHODS: The study included 2 randomly selected groups of subjects aged 50-74 years (1-sample FIT, n=5007; 2-sample FIT, n=3197). The 2-sample group was instructed to collect fecal samples on 2 consecutive days. Subjects were referred for colonoscopy when at least 1 sample tested positive (≥50 ng hemoglobin/mL). RESULTS: Attendance was 61.5% in the 1-sample group (2979 of 4845; 95% confidence interval, 60.1%-62.9%) and 61.3% in the 2-sample group (1875 of 3061; 95% confidence interval, 59.6%-63.0%; P=.84). In the 1-sample group 8.1% tested positive, and in the 2-sample group 12.8% had at least 1 positive test outcome and 5.0% had 2 positive test outcomes (P<.05). When the mean from both test results in the 2-sample group was used, 10.1% had a positive test outcome (P<.05). The detection rates for advanced neoplasia were 3.1% in the 1-sample group, 4.1% in the 2-sample group with at least 1 positive test outcome, 2.5% when both test results were positive, and 3.7% among subjects with the mean from both test results being positive. CONCLUSIONS: There is no difference in attendance for subjects offered 1- or 2-sample FIT screening. The results allow for the development of efficient FIT screening strategies that can be adapted for local colonoscopy capacities, rather than varying the cut-off value in a 1-sample strategy.

Different mechanisms for heterogeneity in leprosy susceptibility can explain disease clustering within households.

The epidemiology of leprosy is characterized by heterogeneity in susceptibility and clustering of disease within households. We aim to assess the extent to which different mechanisms for heterogeneity in leprosy susceptibility can explain household clustering as observed in a large study among contacts of leprosy patients.We used a microsimulation model, parameterizing it with data from over 20,000 contacts of leprosy patients in Bangladesh. We simulated six mechanisms producing heterogeneity in susceptibility: (1) susceptibility was allocated at random to persons (i.e. no additional mechanism), (2) a household factor, (3, 4) a genetic factor (dominant or recessive), or (5, 6) half a household factor and half genetic. We further assumed that a fraction of 5%, 10%, and 20% of the population was susceptible, leading to a total of 18 scenarios to be fitted to the data. We obtained an acceptable fit for each of the six mechanisms, thereby excluding none of the possible underlying mechanisms for heterogeneity of susceptibility to leprosy. However, the distribution of leprosy among contacts did differ between mechanisms, and predicted trends in the declining leprosy case detection were dependent on the assumed mechanism, with genetic-based susceptibility showing the slowest decline. Clustering of leprosy within households is partially caused by an increased transmission within households independent of the leprosy susceptibility mechanism. Even a large and detailed data set on contacts of leprosy patients could not unequivocally reveal the mechanism most likely responsible for heterogeneity in leprosy susceptibility.

Is human fecundity declining in Western countries?

Since Carlsen and co-workers reported in 1992 that sperm counts have decreased during the second half of the last century in Western societies, there has been widespread anxiety about the adverse effects of environmental pollutants on human fecundity. The Carlsen report was followed by several re-analyses of their data set and by many studies on time trends in sperm quality and on secular trends in fecundity. However, the results of these studies were diverse, complex, difficult to interpret and, therefore, less straightforward than the Carlsen report suggested. The claims that population fecundity is declining and that environmental pollutants are involved, can neither be confirmed nor rejected, in our opinion. However, it is of great importance to find out because the possible influence of widespread environmental pollution, which would adversely affect human reproduction, should be a matter of great concern triggering large-scale studies into its causes and possibilities for prevention. The fundamental reason we still do not know whether population fecundity is declining is the lack of an appropriate surveillance system. Is such a system possible? In our opinion, determining total sperm counts (as a measure of male reproductive health) in combination with time to pregnancy (as a measure of couple fecundity) in carefully selected populations is a feasible option for such a monitoring system. If we want to find out whether or not population fecundity will be declining within the following 20-30 years, we must start monitoring now.

Incidence of cervical cancer after several negative smear results by age 50: prospective observational study.

OBJECTIVE: To determine the incidence of cervical cancer after several negative cervical smear tests at different ages. DESIGN: Prospective observational study of incidence of cervical cancer after the third consecutive negative result based on individual level data in a national registry of histopathology and cytopathology (PALGA). SETTING: Netherlands, national data. Population 218,847 women aged 45-54 and 445,382 aged 30-44 at the time of the third negative smear test. MAIN OUTCOME MEASURES: 10 year cumulative incidence of interval cervical cancer. RESULTS: 105 women developed cervical cancer within 2 595,964 woman years at risk after the third negative result at age 30-44 and 42 within 1,278,532 woman years at risk after age 45-54. During follow-up, both age groups had similar levels of screening. After 10 years of follow-up, the cumulative incidence rate of cervical cancer was similar: 41/100,000 (95% confidence interval 33 to 51) in the younger group and 36/100,000 (24 to 52) in the older group (P=0.48). The cumulative incidence rate of cervical intraepithelial neoplasia grade I+ was twice as high in the younger than in the older group (P<0.001). CONCLUSIONS: The risk for cervical cancer after several negative smear results by age 50 is similar to the risk at younger ages. Even after several negative smear results, age is not a good discriminative factor for early cessation of cervical cancer screening.

Feasibility study of adjustment for contamination and non-compliance in a prostate cancer screening trial.

BACKGROUND: The use of PSA as a screening test has become increasingly prevalent in the general population and therefore also in the control arm of the European Randomized study of Screening for Prostate Cancer (ERSPC). We present a feasibility study and impact simulation of a secondary analysis, which imitates a situation where all participants in the study are managed according to their random assignment. METHODS: The results of the Rotterdam section of the ERSPC were adjusted for contamination and non-compliance according to Cuzick et al. [Stat Med 1997; 16:1017-1029]. Endpoints of this analysis were simulated reductions in prostate cancer mortality. RESULTS: Of the men allocated to the screen arm, 27.1% were non-compliant. In the control arm 30.7% had their PSA-level measured by a general practitioner (GP) (i.e., contamination). For a scenario in which the intention-to-screen analysis was assumed to give a decrease in the mortality in the men randomized to screening of 6.7%, the secondary analysis resulted in a decrease of 16.1% for those actually screened. CONCLUSION: Although the definition of contamination as "PSA ever tested" gives an indication of the proportion of contamination, it will be important to differentiate the screening use of PSA from its diagnostic use. For the rest, adjustment for non-compliance and contamination was shown to be feasible in this prostate cancer screening trial. It can therefore be used to carry out a secondary analysis on the definitive outcome of the ERSPC and will provide accurate information for those men who are in fact screened.

Proportion of new HIV infections attributable to herpes simplex 2 increases over time: simulations of the changing role of sexually transmitted infections in sub-Saharan African HIV epidemics.

OBJECTIVE: To understand the changing impact of herpes simplex 2 (HSV-2) and other sexually transmitted infections (STIs) on HIV incidence over time in four sub-Saharan African cities, using simulation models. METHODS: An individual-based stochastic model was fitted to demographic, behavioural and epidemiological data from cross-sectional population-based surveys in four African cities (Kisumu, Kenya; Ndola, Zambia; Yaoundé, Cameroon; and Cotonou, Benin) in 1997. To estimate the proportion of new HIV infections attributable to HSV-2 and other STIs over time, HIV incidence in the fitted model was compared with that in model scenarios in which the cofactor effect of the STIs on HIV susceptibility and infectivity were removed 5, 10, 15, 20 and 25 years into the simulated HIV epidemics. RESULTS: The proportion of incident HIV attributable to HSV-2 infection (the model estimated population attributable fraction (PAF(M))) increased with maturity of the HIV epidemic. In the different cities, the PAF(M) was 8-31% 5 years into the epidemic, but rose to 35-48% 15 years after the introduction of HIV. In contrast, the proportion of incident HIV attributable to chancroid decreased over time with strongest effects five years after HIV introduction, falling to no effect 15 years after. Sensitivity analyses showed that, in the model, recurrent HSV-2 ulcers had more of an impact on HIV incidence than did primary HSV-2 ulcers, and that the effect of HSV-2 on HIV infectivity may be more important for HIV spread than the effect on HIV susceptibility, assuming that HSV-2 has similar cofactor effects on HIV susceptibility and infectivity. The overall impact of other curable STIs on HIV spread (syphilis, gonorrhoea and chlamydia) remained relatively constant over time. CONCLUSIONS: Although HSV-2 appears to have a limited impact on HIV incidence in the early stages of sub-Saharan African HIV epidemics when the epidemic is concentrated in core groups, it has an increasingly large impact as the epidemic progresses. In generalised HIV epidemics where control programmes for curable STIs are already in place, interventions against HSV-2 may have a key role in HIV prevention.

Monitoring a national cancer prevention program: successful changes in cervical cancer screening in the Netherlands.

The success of screening, an important cancer prevention tool, depends on the quality and efficiency of protocols and guidelines for screening and follow-up. However, even centrally organized screening programs such as the Dutch cervical screening program occasionally show problems in performance. To improve this program, the screening scheme, follow-up, administration and financing protocols and guidelines were thoroughly changed in 1996. This study evaluates the consequences for the performance of the national program. Five-year coverage rate, the proportion of screened women sent to follow-up, follow-up compliance and duration, and the yearly number of Pap smears before and after the changes in 1996 were compared. Five-year coverage increased substantially in the added target age groups (30-34, and 54-60 years); in the old target age group (35-53 years) it remained around 80%. The percentage of screened women sent to follow-up decreased from almost 19-3% per screening round, due to a more restrictive use of the Pap 2 classification, and an evidence-based cessation of follow-up of negative smears without endocervical cells. Follow-up compliance has improved, and the average time until a woman is either referred or rejoins the regular screening schedule, has become shorter. The total number of smears, a strong determinant of screening costs, has decreased by 20% primarily due to the changed follow-up recommendations. In conclusion, the 1996 changes in protocols and guidelines, and their implementation have increased coverage and efficiency, and decreased the screening-induced negative side effects.

No difference in HIV incidence and sexual behaviour between out-migrants and residents in rural Manicaland, Zimbabwe.

OBJECTIVES: Migration is associated with HIV infection, but the relationship has been mostly assessed in cross-sectional studies. In a prospective study, we investigated whether out-migrants are a selection of high-risk individuals and whether rural-to-urban migration results in risky sexual behaviour for HIV incidence. METHODS: A population cohort was enrolled in a stratified household census in four different community types in Manicaland, east Zimbabwe, between July 1998 and February 2000, and followed-up after 3 years. Out-migrants to the national capital (Harare), the provincial capital (Mutare) and other study areas were followed-up. A structured questionnaire was administered and an HIV test was conducted at each interview. HIV prevalence and sexual risk behaviour at baseline, and HIV incidence and sexual behaviour during follow-up were compared for out-migrants and residents. RESULTS: At baseline, future migrants were significantly younger, better educated and more likely to be single than residents. For males, migration was highest from subsistence farming areas and roadside trading centres and lowest from estates. After adjusting for age, education, marital status and location, there were no differences in HIV prevalence and sexual risk behaviour between future migrants and residents at baseline, for either sex. No significant differences in HIV incidence or sexual behaviour during follow-up were detected between rural-to-urban out-migrants and residents. CONCLUSIONS: Out-migrants from rural Zimbabwe did not have higher levels of HIV infection or sexual risk behaviour than residents either before or after they moved. These findings may be related to the mature stage of the HIV epidemic and the social and living conditions of migrants in Zimbabwean cities.