Abstract
Franz Halberg died on June 9, 2013, just shy of his 94th birthday. Many readers of the Journal of Biological Rhythms, including myself, considered him one of the “forefathers of chronobiology” (along with Jürgen Aschoff and Colin Pittendrigh). He even gave us the terms we use most, circadian and chronobiology.
Halberg was born in Bistrita, Romania, on July 5, 1919, and moved to the United States a few years after completing medical school. He established himself at the University of Minnesota in 1949 and stayed there until his death six decades later. His success as a scholar is evident in the number of publications that he authored (over 3400), the endurance of his research funding by the National Institutes of Health (Grant GM 013981, renewed 50 times), and the number of honoris causa doctorates (six) that he was awarded by universities in many countries.
Halberg introduced the term circadian in 1959 (Zeitschrift für Vitamin-, Hormon- und Fermentforschung 10: 225-296, 1959). The new word became popular immediately. PubMed lists 436 articles published through the end of 1969 with the word circadian in the title, and the current count of articles with the term circadian in the title, abstract, or indexing field exceeds 68,000. Halberg was a prolific namer of phenomena and areas of research—and he delved into all of them. His many investigations into time patterns of physiological variables, clinical lab results, and pharmacological effectiveness brought the importance of chronobiology to the attention of clinically oriented researchers around the world. His literature review of chronobiology (Annual Review of Physiology 31: 675-725, 1969) was read and cited widely, becoming an ISI “Citation Classic.”
In the early 1960s, Halberg and collaborators developed a powerful tool for the analysis of circadian rhythms: the cosinor procedure, which fits a cosine wave to the data by the principle of least squares, thus providing a statistically sophisticated method to characterize the parameters of biological rhythms. A didactical presentation of the procedure can be found in Chronobiologia 6: 305-323, 1979. Many years later, I had the privilege of serving as his co-author in an article that clarified the relationship between the cosinor and other procedures for biological time series analysis (Biological Rhythm Research 38: 275-325, 2007).
Halberg established, and served as Editor of, the journal Chronobiologia, which was published from 1974 to 1994. From this time on, he concentrated more on his long-lasting interest in applied (medical) aspects of biological rhythms and diverged more and more from the line of research conducted by Aschoff and Pittendrigh. His view of the importance of biological rhythms expanded not only to include rhythms (endogenous or not) at a multitude of frequencies (3-day and 10-year, among others) but to encompass the whole cosmos in what he called chronoastrobiology (e.g., Biomedicine and Pharmacotherapy 57: 24s-30s, 2003). He remained active in research collaborations and publication, concentrating on preventive cardiology and individually timed cancer treatment, until his death.
After meeting Halberg in 2002, I had many intellectual exchanges with him via e-mail, telephone, and in person. I came to know him as a kindly, cultured man of refined taste and manners. With Franz Halberg’s death, the world lost not only the foremost advocate for chronobiology but also a wise and gracious gentleman.