title: The influence of the winter North Atlantic Oscillation index on hospital admissions through diseases of the circulatory system in Lisbon, Portugal.
abstract: The aim of this paper is to analyze the relationship between North Atlantic Oscillation (NAO), meteorological variables, air pollutants, and hospital admissions due to diseases of circulatory systems in Lisbon (Portugal) during winter months (2003-2012). This paper is one of the few studies analyzing the impact of NAO on health through its influence on thermal stress and air pollution and is the first to be conducted in Lisbon. This study uses meteorological data (synthetized into a thermal comfort index), air pollutant metrics, and the NAO index (all clustered in 10-day cycles to overcome daily variability of the NAO index). The relationship between morbidity, thermal comfort index, NAO index, and air pollutants was explored through several linear models adjusted to seasonality through a periodic function. The possible indirect effect between the NAO index and hospital admissions was tested, assuming that NAO (independent variable) is affecting hospital admissions (outcome variable) through thermal discomfort and/or pollution levels (tested as individual mediators). This test was conducted through causal mediation analysis and adjusted for seasonal variation. The results from this study suggest a possible indirect relationship between NAO index and hospital admissions. Although NAO is not significantly associated with hospital admissions, it is significantly associated with CO, PM2.5, NO, and SO2levels, which in turn increase the probability of hospitalization. The discomfort index (built with temperature and relative humidity) is significantly associated with hospital admissions, but its variability is not explained by the NAO index. This study highlights the impacts of the atmospheric circulation patterns on health. Furthermore, understanding the influence of the atmospheric circulation patterns can support the improvement of the existing contingency plans.
authors.affiliation: Centre of Studies on Geography and Spatial Planning, University of Coimbra, Coimbra, Portugal. ricardoalmendra85@gmail.com.
authors.forename: Ricardo
authors.identifier: http://orcid.org/0000-0002-2712-9643
authors.initials: R
authors.lastname: Almendra
authors.affiliation: Centre of Studies on Geography and Spatial Planning, University of Coimbra, Coimbra, Portugal.
authors.forename: Paula
authors.initials: P
authors.lastname: Santana
authors.affiliation: School of Tourism and Maritime Technology, Polytechnic Institute of Leiria, Leiria, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Vasconcelos
authors.affiliation: CEAUL and Department of Mathematics-IST, Universidade de Lisboa, Lisboa, Portugal.
authors.forename: Giovani
authors.initials: G
authors.lastname: Silva
authors.affiliation: Atmospheric Sciences, University of Sao Paulo, Sao Paulo, Brasil.
authors.forename: Fábio
authors.initials: F
authors.lastname: Gonçalves
authors.affiliation: Atmospheric Sciences, University of Sao Paulo, Sao Paulo, Brasil.
authors.forename: Tércio
authors.initials: T
authors.lastname: Ambrizzi
mesh_terms: D000393:Air Pollutants / Q000032:analysis; D002248:Carbon Monoxide / Q000032:analysis; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D002947:Cities / Q000453:epidemiology; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D016014:Linear Models; D009569:Nitric Oxide / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis; D011174:Portugal / Q000453:epidemiology; D012621:Seasons; D013458:Sulfur Dioxide / Q000032:analysis; D014887:Weather
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D013458:Sulfur Dioxide; D009569:Nitric Oxide; D002248:Carbon Monoxide
keywords: Air pollution; Circulatory system diseases; Hospital admissions; North Atlantic Oscillation