!% Circannual death rhythmicity ISSN 13920138. A c t a m e d i c a L i t u a n i c a . 2001. T. 8, Nr. 1 Circannual Rhythmicity of Death Distribution Eliahu Stoupel 1 , Jadvyga Petrauskiene 2 , Uri Gabbay 3 , Ramunë Kaledienë 2 , Evgeny Abramson 4 , Jacqueline Sulkes 4 1 Division of Cardiology and 4 Epidemiology Unit, Rabin Medical Center, Beilinson Campus, Petah Tikva, and 3 Sheba Medical Center, and Tel Aviv University, Tel Aviv, Israel; 2 Kaunas University of Medicine, Kaunas, Lithuania Objectives. Circannual rhythmicity is central to chronobiology. The aim of the present study was to compare the expression and significance of the circan- nual distribution of cardiovascular and non-cardiovascular deaths in Israel and Lithuania. Gender and age differences were also examined. Methods. The Co- sinor analysis was used to determine the significance of the measure of the rhythm parameters: mesor, amplitude and acrophase. We analyzed 344,165 deaths in Lithuania  169,671 cardiovascular-related (IHD, MI, CVA, CHF) over a 96-month period, and 26,627 in Israel  10,727 cardiovascular-related over a 228-month period in addition to 11,704 fatal suicides in Lithuania and 2,964 fatal suicides and 16,911 suicide attempts in Israel. Results and Con- clusions. Both in Lithuania and Israel, the general annual death distribution is significantly rhythmic; the acrophase of cardiovascular deaths occurs in FebruaryMarch (P < 0.0001), for suicide  around June (P < 0.0001). By contrast, for non-cardiovascular deaths, the circannual distribution does not achieve statistical significance in general or for men separately, though it does for women. Cardiovascular- and suicide-related deaths show different annual acrophases. They are temporally inversely correlated to each other and to many environmental physical activity factors. Key words: circannual rhythmicity, death, ischemic heart disease (IHD), stroke, suicide INTRODUCTION In the last few decades, many studies have been carried out to determine the connection between time and different biologic processes, including death. A special scientific discipline known as chronobiolo- gy emerged (1). In addition to the studies concen- trating on circadian (24 hours) distribution of events and mechanisms related to such rhythmicity, annual and more extensive (solar cycle  11 years and mo- re) investigations were provided. The additional background of well-known mecha- nisms involved in the chronobiologic effects has given new results on the effects, especially the cold-re- lated influence on the serotoninmelatonin metabo- lism system (light/darkness effects, etc.) which plays an important role in the function of the CNS, antioxidant processes, behavior and other aspects of human homeostasis. Studies on environmental physical factors such as the solar flux, radiowave propagation, geomagne- tic activity, space proton flux links to death distribu- tion in time have been published in the last few years (24). OBJECTIVES The purpose of this study was to determine the monthly death distribution from such big killers as ischemic heart disease (IHD), stroke (CVA), suicide, accidents, road accidents and hospital mor- tality for a long period of time. We used modern therapeutic measures plus total mortality (data) in two countries  Israel (hospital) and Lithuania (na- tional data). The differences in geographic, climatic and many other parameters were compared. We checked the monthly death distribution from these causes vs. rhythmic, in general and in both genders, and tried to determine the reason for the differen- ces in the annual time distribution of deaths. Address for correspondence: Prof. E. Stoupel, M. D., Division of Cardiology, Rabin Medical Center, Beilinson Campus, Petah Tikva, Israel 49100. Tel: 972-9-7426439. Fax: 972-3-9240489. Mors certa, hora incerta (Latin proverb)