Epidemiological studies are performed to determine the frequency, distribution and causes of diseases. This means that the relevant influencing factors are examined in addition to the diseases. For example, the goal of the Hamburg City Health Study (HCHS), which with 45,000 participants is the largest local health study of the world, is to understand the complex network of interactions between the environment, biology, genetics and lifestyle that underlie diseases. For this purpose, the risk factors for the most frequent illnesses such as heart attack, atrial fibrillation, stroke or dementia are identified, by investigating the influences of genetics, pre-existing conditions, lifestyle and environment on human health. Many epidemiological studies in Europe, Asia, Africa and North America use SAFEĀ® for their samples.