BMC Public Health 2008, 8:126 http://www.biomedcentral.com/1471-2458/8/126 bility that, of those invited, the 'worried well' and 'healthy deprived' would preferentially volunteer, so minimising potential differences between the least and most deprived communities. A further methodological concern was the impact on par- ticipation of the number of questionnaires, investigations and the prospect of having to attend two visits of 1 1/2 hours each for this study. Only 34 participants failed to complete both visits and the full set of evaluations. Partic- ipants stated on a feedback questionnaire that they were highly satisfied with the study process and some saw it as an opportunity to have a complete medical check-up Strengths and Limitations The study achieved its recruitment objectives in terms of the sample size and the nature of the recruits. The depth and range of the evaluations performed will provide important information concerning the relationships between deprivation, obesity, inflammation, atheroscle- rosis and mental outlook. This will enable us to address the hypothesis that the increased prevalence of coronary heart disease, type 2 diabetes and negative mental outlook in a deprived population is attributable in large part to an increased frequency of chronic inflammation, endothelial dysfunction and insulin resistance linked to the more challenging social environment. There are limitations to the design of pSoBid[66]. Since the sample was stratified by age and sex, it is not a true representation of the general population; further, there is bias due to the variation in response rate. The sample was selected from the extremes of deprivation so as to maxim- ise any observed differences and, therefore, provides no information about population gradients. The cross-sec- tional nature of the study means that it will not be possi- ble to identify causal pathways or the temporal relationship between variables. That said, the breadth and depth of data collected, linkage to NHS records, and the population-based nature of pSo- Bid make it an important resource, now and in prospect, for building understanding about the mechanisms that help to explain deprivation-related ill-health. Conclusion The multidisciplinary approach employed in this study will enable a more holistic understanding of the diverse characteristics of individuals who reside in affluent and deprived communities and their influence on health and health inequalities. This study also illustrates the willing- ness of subjects to volunteer for a variety of investigations involving psychological, behavioural, sociological and medical questions and tests including blood analysis. As in other studies it was easier to enrol females than males, older compared to younger people, and the more affluent participants. Linkage to medical records allowed compar- ison of the health characteristics of participants and non- participants, yielding an insight into aspects of volunteer bias in studies of this type. This study also brought together researchers/academics from diverse disciplines to build a more sophisticated understanding of the determi- nants of health inequalities than can be achieved through unidisciplinary approaches. Future analyses will enable an understanding of the relationships between the differ- ent types of measure, and of the pathways that link pov- erty, biology, behaviour and psychology and lead to health inequalities. This article has outlined the study background, design and recruitment. The findings from this study will be pre- sented in future articles. Competing interests The author(s) declares that they have no competing inter- ests. Authors' contributions YV, CJP, DGB, HB, JC, KD, IF, KM, NS, PS and CT contrib- uted equally to conception, design and final approval of the version to be published. YV, CJP and CT have been involved in drafting the manuscript and revising it criti- cally for important intellectual content. VB performed the statistical analysis. AM supervised the recruitment of sub- jects and data collection. Additional material Additional file 1 Flow chart for subjects in pSoBid. Click here for file [http://www.biomedcentral.com/content/supplementary/1471- 2458-8-126-S1.doc] Acknowledgements Thanks are due to administrative staff in the GCPH; Robertson Centre for data management, statistical support & analysis; Health Information & Tech- nology section of NHSGGC for sample selection and analysis; Alasdair Buchanan for GPASS data & analysis; all members of GP Practices who par- ticipated in the study and the participants themselves. This study is funded by the Glasgow Centre for Population Health which is a partnership between NHS Greater Glasgow and Clyde, Glasgow City Council and the University of Glasgow, supported by the Scottish Govern- ment. References 1. Davey Smith G: Socioeconomic differentials. In A life course approach to chronic disease epidemiology Oxford: Oxford University Press; 1997. Page 9 of 11 (page number not for citation purposes)