LAUSR

Living organisms are characterized by circadian mechanisms. The central circadian clock is located within the suprachiasmatic nucleus of the hypothalamus, and peripheral clocks have also been widely found across organisms. Such complex machinery allows living organisms to synchronize and optimally adapt to either their external or their internal environments [1]. On the other hand, circadian misalignment of an organism with its environment may increase cardiovascular risk factors and lead to the development of cardiovascular (CV) diseases [2]. Daylight saving time (DST), which was adopted during the First World War to save energy and is still in use in many countries worldwide, can be a cause of circadian misalignment. Based on concerns about human health, Finland and other northern state members called for the abolition of DST, and a proposal by the European Commission to discontinue the bi-annual shifts has been recently approved by the European Parliament. We aimed to investigate a possible relationship between deaths from circulatory diseases, i.e., cardiovascular and cerebrovascular diseases, and DST transitions in a large Italian region. Analyses were carried out with the archive of mortality records from January 2000 to December 2015 of the Veneto region of Italy (≈ 4,900,000 inhabitants). The causes of death were coded following the rules established by the World Health Organization, according to ICD-9 until 2006 and to ICD-10 from 2007 onward. Deaths were classified according to broad categories used in standard reports of mortality statistics. The number of deaths observed in each of the 7 days after the spring and the autumn shifts (post-transitional weeks) was compared with the mean number of deaths registered on the corresponding day of the week of the 2 weeks before and the 2 weeks after the post-transitional week (referred to as the ‘reference period’). The analysis was carried out for all deaths from circulatory diseases (ICD-9 codes 390–459, ICD-10 I00–I99), in the whole study population and for subjects aged < 65 and ≥ 65 years. Furthermore, deaths from cerebrovascular diseases (ICD-9 430–438, ICD-10 I60–I69), ischaemic heart diseases (ICD-9 410–414, ICD-10 I20–I25), and all other circulatory diseases were investigated. Regarding cerebrovascular and ischaemic heart diseases, such categories included both acute and chronic conditions. A sensitivity analysis limited to deaths from acute myocardial infarction (AMI, ICD-9 410, ICD-10 I21–I22) was performed. The study had enough power to detect a statistically significant 3% excess mortality for all circulatory deaths (approximately 5000 deaths in the post-transitional weeks over the study period). The 95% confidence interval of the ratio of deaths observed in the post-transitional weeks with respect to that * Roberto Manfredini [email protected]