The Berlin Initiative Study (BIS) is a population-based cohort study exploring the epidemiology of chronic kidney disease in old age1. The BIS was started in 2009 and has been going on since then. The main motivation for initiating this cohort is the general lack of data about older adults and especially with regard to chronic kidney disease (CKD). CKD prevalence rates howe- ver, are said to rise in older age with some even speaking of a “CKD epidemic” among elderly people. In the framework of the ongoing demographic shift this would have major health implications. Others argue that a certain decrease of kidney function is due to a normal aging process and has no pathologic meaning.
Two part study design
The BIS consists of a longitudinal part, containing bi-annual follow-up visits to catch incident cases of CKD and follow the natural course of kidney function over time and to assess associated risk factors as well as cardiovascular outcomes such as myorcardial infarction, stroke and death to find out about the clinical meaning of re- duced kidney function in older age. 2.069 individuals aged at least 70 (mean age 80 at baseline) were included. Using face to face interviews questions regarding life- style factors, comorbidities, medication and frailty (in cooperation with Prof. Dr. A. Kuhlmey, Inst. for social medicine) are addressed. Additionally blood and urine- samples for routine analysis and bio- banking are obtained including genetics as well as measurement of anthropometric variables. Thus, the BIS is a very well cha- racterised cohort of older adults.
The Team of the Berlin Initiative Study Berlin, Charité
In addition to the longitudinal part a cross-sectional analysis for exact assess- ment of kidney function (glomerular fil- tration rate = GFR) was carried out with the help of a an iohexol clearance as gold standard in a subsample of 600 participants (mean age 79) and an exact (measured) GFR was assessed. The aim was the crea- tion of an age-adapted new GFR estima- tion equation as current equations such as the MDRD- or CKD-EPI-equations were not validated in older age and potentially under- or overestimate true GFR in old age considerably. This goal was reached by de- veloping two novel equations (“BIS-equa- tions”) which were published recently in Annals of Internal Medicine2.
Extension of research perspective and follow-up time
In summary, by both, its clinical and socio-gerontologic phenotyping and in- frastructure the BIS offers a unique opportunity to address research questions from different fields of geriatric medicine and aging research. What started as a mainly nephrologically oriented cohort study has extended its research perspective into fields of frailty assessment, geriatric healthcare resources, and clinical chemistry. After three study visits covering an individual follow-up time of four years the BIS is fortunately going to be funded with an additional grant enabling us to prolong the BIS follow-up time to six years. The on- going financial support of the BIS has been granted by the Kuratorium für Dialyse und Nierentransplantation (KfH) Foundation of Preventive Medicine.
In the context of demographic changes and the fact that older adults are underrepre- sented in most studies this has high clinical and public health relevance. http://bis.charite.de
1. Schaeffner, ES, van der Giet, M, Gae- deke, J, Tolle, M, Ebert, N, Kuhlmann, MK, Martus, P: The Berlin initiative study: the methodology of exploring kidney function in the elderly by combining a longitudinal and cross-sectional approach. Eur J Epide- miol, 25: 203-210, 2010.
2. Schaeffner, ES, Ebert, N, Delanaye, P, Frei, U, Gaedeke, J, Jakob, O, Kuhlmann, MK, Schuchardt, M, Tolle, M, Ziebig, R, van der Giet, M, Martus, P: Two novel equations to estimate kidney function in persons aged 70 years or older. Ann Intern Med, 157: 471-481, 2012.