The last few decades have seen a marked increase in mean life expectancy in Central Europe. This has made elderly people and their quality of life a matter of ever-increasing medical concern. Available data from the United States and Scandinavia relating to erectile dysfunction (ED) do not enable us to draw valid conclusions about the current situation in Germany. The aim of the present study was to evaluate the epidemiology of male sexuality in Germany, and the proportion of men who need medical treatment because of increased suffering from this.A newly developed and validated questionnaire on male erectile dysfunction was mailed to a representative population sample of 8000 men, 30±80 y of age in the Cologne urban district.The response included 4489 evaluable replies (56.1%). The response rates in different age groups ranged from 49.2% to 68.4%. Regular sexual activity was reported by 96.0% (youngest age group) to 71.3% (oldest group). There were 31.5%±44% of responders who were dissatis®ed with their current sex life. The prevalence of ED was 19.2%, with a steep age-related increase (2.3± 53.4%) and a high co-morbidity of ED with hypertension, diabetes, pelvic surgery and`lower urinary tract symptoms'. When treatment need was de®ned by co-occurence of ED and dissatisfaction with sex life, 6.9% men required treatment for ED. Oral treatment of ED was preferred by 73.8% of respondents. There were 46.2% respondents who were willing to contribute more than DM 50 (25 Euro) per month for ED treatment.We conclude that regular sexual activity is a normal ®nding in advanced age. ED is a frequent disorder, contributing to dissatisfaction with sex life in a considerable proportion of men. The high burden of ED is re¯ected in willingness to pay for treatment. ED is frequently associated with chronic diseases. Therefore adequate diagnostic workup is essential, to offer patients individually adapted treatment. General non-reimbursability of treatment for ED appears to be unacceptable.

A method for group sequential trials that is based on the inverse normal method for combining the results of the separate stages is proposed. Without exaggerating the Type I error rate, this method enables data-driven sample size reassessments during the course of the study. It uses the stopping boundaries of the classical group sequential tests. Furthermore, exact test procedures may be derived for a wide range of applications. The procedure is compared with the classical designs in terms of power and expected sample size.

'Multistage testing with adaptive designs' was the title of an article by Peter Bauer that appeared 1989 in the German journal Biometrie und Informatik in Medizin und Biologie. The journal does not exist anymore but the methodology found widespread interest in the scientific community over the past 25 years. The use of such multistage adaptive designs raised many controversial discussions from the beginning on, especially after the publication by Bauer and Köhne 1994 in Biometrics: Broad enthusiasm about potential applications of such designs faced critical positions regarding their statistical efficiency. Despite, or possibly because of, this controversy, the methodology and its areas of applications grew steadily over the years, with significant contributions from statisticians working in academia, industry and agencies around the world. In the meantime, such type of adaptive designs have become the subject of two major regulatory guidance documents in the US and Europe and the field is still evolving. Developments are particularly noteworthy in the most important applications of adaptive designs, including sample size reassessment, treatment selection procedures, and population enrichment designs. In this article, we summarize the developments over the past 25 years from different perspectives. We provide a historical overview of the early days, review the key methodological concepts and summarize regulatory and industry perspectives on such designs. Then, we illustrate the application of adaptive designs with three case studies, including unblinded sample size reassessment, adaptive treatment selection, and adaptive endpoint selection. We also discuss the availability of software for evaluating and performing such designs. We conclude with a critical review of how expectations from the beginning were fulfilled, and -if not -discuss potential reasons why this did not happen.

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