Viennese study maps genetic foundations of the internal clock

What the "Circadian Imbalance Index" measures

"Mit unserer Studie konnten wir erstmals die genetische Architektur des Circadian Imbalance Index charakterisieren," said first author Magdalena Zebrowska. The researchers identified 27 regions of the genome that are associated with the "Circadian Imbalance Index." Several of the genes found had already been linked in studies to the regulation of the internal clock or to the biological signaling pathways involved.

Study leader Eva Schernhammer provided further context for the results: "Die Ergebnisse sprechen dafür, dass die Anfälligkeit für eine zirkadiane Dysbalance nicht durch einen einzelnen biologischen Mechanismus bestimmt wird, sondern durch das Zusammenspiel mehrerer genetischer Einflüsse, die sich in unterschiedlichen verhaltensbezogenen, psychologischen und biologischen Eigenschaften widerspiegeln. Der Index ermöglicht es, diese verschiedenen Dimensionen gemeinsam zu betrachten und ihre genetischen Zusammenhänge zu untersuchen," added study leader Eva Schernhammer.

Why the internal clock matters

The background to the study is the significance of the circadian rhythm for the human organism. The circadian rhythm is a central biological pacemaker of the human organism and is coordinated in a control center in the brain, the suprachiasmatic nucleus in the hypothalamus. It synchronizes bodily functions via light signals from the environment and ensures that physiological processes are temporally coordinated with one another. It operates roughly on a 24-hour rhythm.

A research team led by the Medical University of Vienna has found that susceptibility to this cannot be explained by a single factor, but rather arises from the interplay of several characteristics with partly genetic foundations. The study thus supports the hypothesis that disorders of the internal clock are a polygenetic phenomenon, that is, jointly influenced by many small genetic effects.

Specifically, the analysis meant: the researchers systematically searched the genome of the more than 312,000 participants for statistical connections between genetic variants and the values in the "Circadian Imbalance Index." Regions of the genome that occurred significantly more frequently in individuals with elevated index values were classified as relevant. The 27 identified regions are distributed across multiple chromosomes and include genes involved, among other things, in the control of the day-night rhythm, in hormonal signals, and in metabolic processes.

Significance for future research

At the same time, Schernhammer emphasized that the genetic findings explain only part of the overall picture. In addition to genetic factors, lifestyle, age, occupational activity, light exposure, and social conditions also play a role in determining how stably or vulnerably the internal clock functions. The study therefore primarily shows the biological points at which future research could begin.

For a clinical application in risk prediction, further investigations would be required, according to the team. Specifically, the researchers cited, among other things, the need to replicate the results in independent population groups, to characterize more precisely the underlying biological mechanisms of the identified gene regions, and to investigate possible interactions with environmental factors. In the long term, such findings could help identify at-risk individuals earlier and provide more targeted advice on measures such as light exposure, sleep hygiene, or daily routine.

The publication joins a growing number of studies examining the genetic foundations of sleep, chronotype, and circadian regulation. The Medical University of Vienna sees the project as a contribution to advancing prevention and personalized medicine in the field of sleep and rhythm research. The APA report on the study appeared on 22 July 2026.

Data basis: UK Biobank

The work is internationally embedded through the use of the British UK Biobank, which provides samples and data from voluntary participants for scientific analyses. Such large cohorts are regarded as a prerequisite for being able to make statistically robust statements about the connection between genetic characteristics and complex phenotypes such as circadian imbalance.