We are extremely sad to hear that our long-term colleague from the Institute of Neurosciences and Medicine in Novosibirsk, Konstantin Danilenko M.D., died on 18 January 2023.

Konstantin was an excellent and precise scientist and clinician, a gentle and reliable friend, and a stalwart pillar of the light therapy research community. Before joining our group here in Basel in 1995, he had already published studies on Seasonal Affective Disorder and light therapy at the northern Siberian latitudes with his mentor Dr. Arcady Putilov. His crucial contributions in our laboratory showed that a single dawn simulation at low light intensities phase advances the human circadian core body rhythms. Returning to Novosibirsk, he set up a constant routine lab in his next-door apartment and carried-out some unique and demanding studies: he found that six daily dawn signals were able to forestall the natural delay drift occurring without morning light, and that sleep per se was only a weak Zeitgeber in humans. A series of ophthalmologic investigations were initiated together with Dr. Marc Hébert from Canada, to document possible circadian rhythms in human rod or cone photoreceptor function. Importantly, his group developed the objective statistical “hockey-stick” method to estimate dim light melatonin onset, which is now widely used instead of fixed or dynamic thresholds or subjective estimates.

His broad-ranging interests encompassed both pragmatic clinical applications of chronotherapy and curiosity about its underlying mechanisms.

In Basel, Kostya had an extra important function, regularly training every Tuesday evening as a defensive midfield football player for the FC PUK (with our former colleague Kurt Kräuchi), in the team that won the international hospital indoor football tournament in 1998.

We lose a very intelligent, nice and always patient friend and collaborator, and we send our sincere condolences to his family and his colleagues in Novosibirsk.