Randomised trials have shown that aspirin reduces the short-term risk of recurrent colorectal adenomas in patients with a history of adenomas or cancer, but large trials have shown no effect in primary prevention of colorectal cancer during 10 years' follow-up. However, the delay from the early development of adenoma to presentation with cancer is at least 10 years. We aimed to assess the longer-term effect of aspirin on the incidence of cancers.

The effect of different classes of antihypertensive drugs on incident diabetes mellitus is controversial because traditional meta-analyses are hindered by heterogeneity across trials and the absence of trials comparing angiotensin-converting-enzyme (ACE) inhibitors with angiotensin-receptor blockers (ARB). We therefore undertook a network meta-analysis, which accounts for both direct and indirect comparisons to assess the effects of antihypertensive agents on incident diabetes.

Despite three decades of prenatal screening for congenital toxoplasmosis in some European countries, uncertainty remains about the effectiveness of prenatal treatment.

Since nearly half of new HIV infections worldwide occur among young people aged 15-24 years, changing sexual behaviour in this group will be crucial in tackling the pandemic. Qualitative research is starting to reveal how social and cultural forces shape young people's sexual behaviour and can help explain why information campaigns and condom distribution programmes alone are often not enough to change it. We undertook a systematic review to identify key themes emerging from such research, to help inform policymakers developing sexual health programmes, and guide future research.

Studies of the association between obesity, and total mortality and cardiovascular events in patients with coronary artery disease (CAD) have shown contradictory results. We undertook a systematic review to determine the extent and nature of this association.

Angiotensin-converting-enzyme (ACE) inhibitors reduce cardiovascular mortality and morbidity in patients with heart failure or left ventricular systolic dysfunction (LVSD). Three large trials have assessed the effect of ACE inhibitors in stable patients without these conditions but with atherosclerosis. We undertook a systematic review of the Heart Outcomes Prevention Evaluation (HOPE), the European trial on Reduction Of cardiac events with Perindopril among patients with stable coronary Artery disease (EUROPA), and the Prevention of Events with ACE inhibition (PEACE) studies to determine the consistency with which ACE inhibitors reduce total mortality and fatal and non-fatal cardiovascular events.

Few attempts have been made to estimate the public return on investment in medical research. The total costs and benefits to society of a clinical trial, the final step in testing an intervention, can be estimated by evaluating the effect of trial results on medical care and health.

The reduction of maternal deaths is a key international development goal. Evidence-based health policies and programmes aiming to reduce maternal deaths need reliable and valid information. We undertook a systematic review to determine the distribution of causes of maternal deaths.

Conservative methods to treat cervical intraepithelial neoplasia and microinvasive cervical cancer are commonly used in young women because of the advent of effective screening programmes. In a meta-analysis, we investigated the effect of these procedures on subsequent fertility and pregnancy outcomes.

Near-patient testing has made self-monitoring of anticoagulation with warfarin feasible, and several trials have suggested that such monitoring might be equal to or better than standard monitoring. We did a systematic review and meta-analysis of all randomised controlled trials that assessed the effects of self-monitoring or self-management (self-testing and self-dosage) of anticoagulation compared with standard monitoring.

Use of antivirals is recommended for the control of seasonal and pandemic influenza. Our aim was to review the evidence of efficacy, effectiveness, and safety of registered antivirals against naturally occurring influenza in healthy adults.

Liquid-based cytology is reported to increase the sensitivity of cervical cytology and the proportion of slides that are satisfactory for assessment, in comparison with conventional cytology. Although some countries have changed to liquid-based cytology for cervical screening, controversy remains. We reviewed the published work to assess the performance of liquid-based cytology relative to conventional cytology in primary studies assessed to be of low, medium, or high methodological quality.

A consensus has emerged that angiotensin-converting-enzyme (ACE) inhibitors and angiotensin-II receptor blockers (ARBs) have specific renoprotective effects. Guidelines specify that these are the drugs of choice for the treatment of hypertension in patients with renal disease. We sought to determine to what extent this consensus is supported by the available evidence.

Influenza vaccination of elderly individuals is recommended worldwide. Our aim was to review the evidence of efficacy and effectiveness of influenza vaccines in individuals aged 65 years or older.

Antiviral prophylaxis is commonly used in recipients of solid-organ transplants with the aim of preventing the clinical syndrome associated with cytomegalovirus infection. We undertook a systematic review to investigate whether this approach affects risks of cytomegalovirus disease and death.

Valid information about cause-specific child mortality and morbidity is an essential foundation for national and international health policy. We undertook a systematic review to investigate the geographical dispersion of and time trends in publication for policy-relevant information about children's health and to assess associations between the availability of reliable data and poverty.

Schistosomiasis is one of the world's most prevalent infections, yet its effect on the global burden of disease is controversial. Published disability-adjusted life-year (DALY) estimates suggest that the average effect of schistosome infection is quite small, although this is disputed. To develop an evidenced-based reassessment of schistosomiasis-related disability, we did a systematic review of data on disability-associated outcomes for all forms of schistosomiasis.

About 13 million people are classified as refugees worldwide, and many more former refugees have been granted citizenship in their new countries. However, the prevalence of post-traumatic stress disorder, major depression, or psychotic illnesses in these individuals is not known. We did a systematic review of surveys about these disorders in general refugee populations in western countries.

We aimed to assess evidence of efficacy and effectiveness of live attenuated and inactivated influenza vaccines in children up to 16 years of age.

There is continuing debate on the extent of the effects of media violence on children and young people, and how to investigate these effects. The aim of this review is to consider the research evidence from a public-health perspective. A search of published work revealed five meta-analytic reviews and one quasi-systematic review, all of which were from North America. There is consistent evidence that violent imagery in television, film and video, and computer games has substantial short-term effects on arousal, thoughts, and emotions, increasing the likelihood of aggressive or fearful behaviour in younger children, especially in boys. The evidence becomes inconsistent when considering older children and teenagers, and long-term outcomes for all ages. The multifactorial nature of aggression is emphasised, together with the methodological difficulties of showing causation. Nevertheless, a small but significant association is shown in the research, with an effect size that has a substantial effect on public health. By contrast, only weak evidence from correlation studies links media violence directly to crime.