Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Seasonal blood pressure changes: which ambient temperature should we consider? Pietro Amedeo Modesti a and Gianfranco Parati b,c See original paper on page 1582 M ost countries suffer from 5 to 30% excess winter mortality (EWM), the majority of additional winter deaths being caused by cerebrovascular diseases, which may be related, among other factors, to the pressor effect of cold weather. The possibility to control the blood pressure (BP) changes associated with low environmental temperature is thus a relevant issue, for both physicians and public health officers. In this regard, previous investi- gations, as well as recommendations given to citizens, have been developing into two different directions, underlying the importance of indoor or outdoor temperature, respect- ively, although the health impact of cold strain seems to be a more complex issue. The diffusion of effective systems for heating homes has always been considered as an important element in the promotion of public health, especially in world regions characterized by cold winters. To reduce the environmental impact of ambient indoor heating and at the same time to optimize its effects, there is now increasing attention towards technologies that can improve heating systems efficiency, by reducing heat loss from homes walls, doors and windows. These efforts seem to have been rewarding because, using a 5-year moving average, which smoothens out short- term fluctuations, excess winter deaths have been declining steadily since 1960 – 1961 up to current times. However, the importance of thermal efficiency standards in relation to housing is not equally felt as an important issue in the different European countries. This may be partly due to the observation that, in Europe, although mortality does increase as weather gets colder, differences in outdoor temperature only explain a small amount of the variance in winter mortality, and high levels of EWM can occur during relatively mild winters [1]. More precisely, Healey [2] showed that EWM varied widely within Europe, and that countries with very low outdoor winter temperatures in Scandinavia and Northern Europe, such as Finland and Germany, somehow unexpectedly had very low rates of EWM, whereas countries with very mild winter tempera- tures in Southern Europe, such as Portugal and Spain, displayed very high rates of EWM. In fact, European countries with milder winters also tend to have homes with poorer thermal efficiency (e.g. fewer homes have cavity wall insulation and double glazing), which makes it harder to keep homes constantly warm during winter [2]. Available data on cross-country thermal efficiency standards in housing indicate that those countries with the poorest thermal housing efficiency (Portugal, Greece, Ireland, the UK) do indeed demonstrate the highest excess winter mortality [2]. The same epidemiological data can, however, be read in a different perspective. The behavioural capability to cope with cold weather was also shown to display quite wide variations within Europe. The Eurowinter group [3] reported that, compared with people living in countries with cold winters, individuals from warmer countries were less likely to wear warm protective clothing in cold weather. The same international survey showed an inde- pendent association of outdoor, as well as indoor, low ambient temperatures with excess mortality in such countries during cold weather [3]. People in the retirement age are particularly vulnerable to winter temperatures, and show higher mortality rates with cold weather. Indeed, in Great Britain, blue collars at working age (50–59 years) had lower cold weather- related mortality as compared either with their wives of similar age or with men of the same social class after retirement age (65–74 years). These observations suggest that body internal heat production from manual work protected men of working age against daytime cold- related stress, as well as against the associated risk of higher mortality. Moreover, elderly people living in sheltered houses that were fully heated, but who often went outdoors, had as much winter mortality as the general elderly population including those living in less well heated houses [4]. This is not surprising, since the majority of additional winter deaths are caused by cerebrovascular diseases, and, for example, cold temperature-related stress affecting people waiting at a Journal of Hypertension 2014, 32:1577–1579 a Department of Medicina Sperimentale e Clinica, University of Florence, Florence, b Department of Cardiovascular, Neural and Metabolic Sciences, S. Luca Hospital, Istituto Auxologico Italiano and c Department of Health Sciences, University of Milano- Bicocca, Milan, Italy Correspondence to Gianfranco Parati, MD, FESC, Cardiology Unit, San Luca Hospital, Istituto Auxologico Italiano, Piazzale Brescia 20, Milan 20149, Italy. Tel: +39 02 61911 2949; fax: +39 02 61911 2956; e-mail: gianfranco.parati@unimib.it J Hypertens 32:1577–1579 ß 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. DOI:10.1097/HJH.0000000000000262 Journal of Hypertension www.jhypertension.com 1577 Editorial Comment