Cohort Profile: UK COSMOS—a UK cohort for study of environment and health

The United Kingdom COhort Study of MObile phone uSe and health (UK COSMOS) is a prospective cohort study established to investigate the possible health effects associated with long-term use of mobile phones and other wireless technologies, to inform public health policy in the UK and beyond. UK COSMOS is part of the international COSMOS cohort study consortium (the UK, Sweden, The Netherlands, Finland, Denmark and France) on mobile phones and health, which has over 300 000 study participants across the six partner countries. Details of consortium partners are given at [www.ukcosmos.org]. A large prospective cohort study of mobile phone users with long-term follow-up has been recommended as a high priority by the World Health Organization. This reflects both scientific uncertainty and public concern regarding possible health effects of mobile phone use. Radiofrequency electromagnetic fields have recently been classified as possibly carcinogenic to humans (Group 2B) on the basis of limited evidence concerning risk of brain cancers. Results from the Interphone study, the largest case-control study on brain cancer to date, suggested possible increased risks of glioma at the highest levels of mobile phone use, but interpretation was unclear and the possible health effects of long-term heavy use of mobile phones remain uncertain. The COSMOS study was designed to investigate this question while addressing limitations of previous studies. Its cohort study design, with prospective exposure assessment, is less prone to potential selection and recall biases associated with case-control studies such as Interphone. Unlike the case-control approach, it addresses a wide range of disease outcomes of importance for public health in one investigation, including neurodegenerative disease, stroke and depression which have rarely been studied; previous studies have focused on few outcomes, mainly tumours of the brain and head. Large long-term cohort studies have huge potential to increase understanding of environmental exposures and disease and thus improve the health of current and future generations, but require sustained investment from funders and continued involvement by participants. To maximize the value of this investment and the benefit to public health, UK COSMOS is not only collecting data to address the question of mobile phones and health, but also has obtained extensive data on wider environmental exposures, lifestyle and demographics, so as to address a wide range of environment and health questions. With over 100 000 participants, UK COSMOS is the UK’s fourth largest cohort study and the largest cohort in the international COSMOS consortium. The UK COSMOS study protocol and subsequent amendments