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The effect of birthplace on heat tolerance and mortality in Italy 1980’-89
No full textIntroduction: The temperature2mortality relationship follows a well known ‘J V shape’ pattern with mortality excesses at cold and hot temperatures, while the value of minimum mortality temperature (MMT) is used as a proxy of population heat tolerance. As MMT is higher for people living in warmer places, it has been argued that populations will adapt to temperature changes. Objective: To test this notion by taking advantage of a huge migratory flux that occurred in Italy during the 1950s, when large numbers of unemployed from the south moved to the industrialising north-western regions. We analysed, through an ecological study, the mortality2 temperature relationships among residents of Milan (Lombardy) who died between 1980 and 1989, by groups identified by birthplace. We also analysed mortality among Sicilian born residents of Palermo (Sicily). Methods: Log linear models were used to fit daily death count data as a function of different explanatory variables: months, weekdays, holiday, influenza epidemics, temperature, and relative humidity. Results: The pattern of mortality2temperature curves differed by birthplace. Curves for natives of Lombardy showed two breakpoints at 19 ̊C (MMT) and 26 ̊C, with no risk for temperatures between two breakpoints: mortality rose sharply over 26 ̊C. For natives of Sicily, residing either in Milan or in Palermo, only one breakpoint emerged at 23 ̊C (MMT), and they shared the same curve pattern and the same increase in mortality risks over this value. Conclusions: Results suggest that heat tolerance in populations could be modulated by outdoor temperatures experienced early in life, and complete acclimatisation may not occur if external environmental temperatures increase
Inquinamento Atmosferico e salute a Taranto
No full textIntroduzione Risulta oggi sempre più importante capire se i cambiamenti climatici in atto possono indurre modificazione nei profili di mortalità ed in particolare nella relazione mortalità temperatura. Si è ipotizzato che un aumento di temperatura può prevenire la mortalità associata al freddo, ma quali le conseguenze sugli effetti del caldo? Dati i notevoli flussi migratori avvenuti a metà del secolo scorso entro l’Italia, è possibile oggi identificare, nei residenti in città come Torino, gruppi omogenei per area di nascita per i quali valutare gli effetti acuti della temperatura. Materiali e Metodi Nello Studio Logitudinale Torinese, per il periodo 1972-2002, i dati di mortalità, con la causa del decesso, sono stati accoppiati con i dati anagrafici, permettendo di avere ulteriori informazioni sul luogo di nascita e di immigrazione. Abbiamo quindi identificato due gruppi di residenti in Torino: 1) residenti nati al Sud, cioè immigrati, quindi cresciuti in aree mediamente più calde e 2) residenti nati al Nord , cioè nativi, quindi cresciuti in aree mediamente più fredde. Il luogo di nascita diverso dal luogo di immigrazione e’ stato escluso. Sono stati esaminati quattro periodi (1972-79, 1980-87, 1988-95, 1996-2002) e due gruppi di cause di morte naturali (ICD.9:1-799) e cardiovascolari (ICD.9:390-459). Per le cause respiratorie le frequenze per gli immigrati erano troppo basse. Le temperature medie giornaliere sono stati fornite dall’ARPA Piemonte. Alle serie temporali di dati giornalieri è stato adattato un modello log-lineare di regressione Poissoniana; in cui si sono incluse anche le variabili categoriali anno, mese, festività, giorni della settimana. Per la relazione non-lineare mortalitàtemperatura è stata inclusa un’approssimazione a linee spezzate (Muggeo, 2003). Le stime combinate dei quattro periodi si sono ottenute con metanalisi ad effetti fissi. Risultati Nei trent’anni esaminati la mortalità naturale e’ passata da 7000 decessi negli anni ’70 a 4500 negli anni 2000 per i nativi a da 1300 a 2400 negli immigrati. Questo andamento rispecchia da un lato lo spopolamento della città di Torino verso le periferie, e dall’altro l’invecchiamento di coloro che hanno fatto parte del flusso migratorio degli anni ’50. Dopo aver aggiustato per stagionalità e variabili temporali abbiamo osservato che tra i residenti deceduti a Torino i rischi di mortalità per cause naturali o cause cardiovascolari associati all’aumento di 1°C di temperatura nei tre giorni precedenti sono minori per coloro sono nati al Sud Italia, e quindi cresciuti a temperature più calde rispetto ai residenti nati al Nord. Invece i nativi del Nord mostrano rischi di mortalità associati al freddo, cioè alla diminuzione di 1°C di temperatura inferiori agli immigrati dal Sud Italia. Si osserva che in generale i rischi sono più alti per il caldo che per il freddo. Gli stessi risultati si osservano per le sole età anziane (maggiori di 65 o 75 anni). Lo stato socio-economico, che si suppone inferiore negli immigrati, potrebbe agire da confondente ma dovrebbe aumentare i rischi per il freddo negli immigrati,e non alterare quindi i risultati. Non e’ facile ipotizzare quale meccanismo potrebbe permettere agli immigrati di sopportare meglio il caldo e peggio il freddo: avere abitudini o stili di vita che aiutano a tollerare il caldo ma non il freddo, quali dieta, modo di vestire etc? Vi può essere un contributo del frequente ritorno nei luoghi di nascita nelle vacanze estive? Può essere verosimile ipotizzare che il meccanismo di termoregolazione raggiunga in gioventù un equilibrio in sintonia con l’ambiente circostante e che tale meccanismo mal si adatti a cambiamenti più radicali di temperatura esterna. L’ipotesi è interessante ma altre indagini sono necessarie
A note on (basic) Principal Components Analysis
No full textThis paper provides some issues, known but somewhat little stressed, on using the conventional covariance or correlation matrix when performing the simple PCA. The paper also proposes a new simple alternative by providing some evidence, via real-data analysis and some simulation experiments, supporting the proposa
Modelling trend in break-point estimation: an assessment of the heat tolerance and temperature effects in four Italian cities
No full textThis paper deals with detecting trend in break-point estimation when some segmented relationship is met in each sub-sample of data. Based on iterative fitting of linear model, the procedure does not depend on the type of the response variable and always reaches the solution in deterministic model. Here the method is applied in mortality time series data to model the heat-tolerance with respect to local temperature in four Italian cities. In order to take into account possible different heterogeneity in each town, an Extend Quasi Likelihood approach is used, allowing joint modelling of mean and dispersion
Joint modelling of non-crossing additive quantile regression via constrained B-spline varying coefficients
No full textWe present a unified framework able to fit the entire quantile process, namely to estimate simultaneously multiple non-crossing quantile curves. The framework relies on assuming each regression parameter varies smoothly across the percentile direction according to B-splines whose coefficients obey proper restrictions. Multiple linear and penalized smooth terms are allowed and the corresponding tuning parameters are estimated efficiently as part of the model fitting. Monotonicity and concavity constraints on the smoothed relationships are also easily accounted for in the framework. Simulation results provide evidence our proposal exhibits good statistical performance with respect to competitors while guaranteeing the non-crossing property and modest computational load. Analyses on a real dataset related to vocabulary size growth are presented to illustrate the model capability in practice
Reference growth charts for assessing growth performance of Posidonia oceanica (L.) Delile
No full textPosidonia oceanica is considered a key species due to its different roles as primary producer, substrate for many species, shoreline erosion protector and long-term carbon store (1).The importance of P. oceanicahas stimulated several studies aimed at quantifying its status. In particular growth performance of rhizomes has become among the most used descriptors for monitoring changes of P. oceanicameadows induced by human or naturalexogenous factors (2). However, ability to detect any change of growth in space or in time is often confounded by natural age-induced variations, which involves serious interpretation problems (3). A general approach adopted to overcome this problem is to build growth charts as reference tool for comparison purposes. Charts describing patterns of biometric features conditioned to age are increasingly used as comparison tools, even if almost exclusively in Auxology(4). Their use can be extended to other disciplines, including ecological studies, although very large data sets are required for obtaining reliable estimates and curves should be flexible enough to account for non-linear growth pattern over age (5). In this work reference growth charts involving different P. oceanicagrowth performance measures (speed of growth and primary production of rhizomes) will be presented. Curves have been built using proper statistical frameworks (GLMM, Segmented and Quantile Regressions), based on more than 13000 annualgrowth data recorded by lepidochronology (6) on about 1600 shoots collected at 4–32 m depth range along Sicilian coasts.Growth patterns exhibited distinct trends as regards the relationships with depth: neither speed of growth nor primary production of rhizomes depended on depth until 14 m, while at deeper stands significant linear decrease by 3.5–2.0% for 1 m increase in depth was observed, due to light and sedimentation reduction. The considerable size of the dataset allowed to estimate the accurate shapes of the percentile curves (from 5thto 95th), revealing non monotonic relationships of growth with respect to shoot age with an initial increase followed by an overall decrease of 40% during the following years of the explored lifespan. The accompanying model-based classification procedures presented, will allow to obtain comparable results also when age of shoots is largely different (up to 20 years) (7). The growth charts may represent a noteworthy tool for researchers involved in studying of different aspects of seagrass monitoring. It is hoped that the proposed framework will facilitate assessment of growth performance status and comparative analysis of growth data from different populations around the Mediterranean Se
The effect of birthplace on heat tolerance and mortality in Milan, Italy, 1980-1989
No full textThe temperature-mortality relationship follows a well-known J-V shaped pattern with mortality excesses recorded at cold and hot temperatures, and minimum at some optimal value, referred as Minimum Mortality Temperature (MMT). As the MMT, which is used to measure the population heat-tolerance, is higher for people living in warmer places, it has been argued that populations will adapt to temperature changes. We tested this notion by taking advantage of a huge migratory flow that occurred in Italy during the 1950s, when a large number of unemployed people moved from the southern to the industrializing north-western regions. We have analyzed mortality-temperature relationships in Milan residents, split by groups identified by area of birth. In order to obtain estimates of the temperature-related risks, log-linear models have been used to fit daily death count data as a function of different explanatory variables. Results suggest that mortality risks differ by birthplace, regardless of the place of residence, namely heat tolerance in adult life could be modulated by outdoor temperature experienced early in life. This indicates that no complete adaptation might occur with rising external environmental temperature
Heat tolerance and mortality by birth-area
No full textBackground: The temperature-mortality relationship follows a wellknown ‘J-V shape’ pattern where the value of Minimum Mortality Temperature (MMT) is used as a proxy of population heat-tolerance. In Italy, during the fifties a huge amount of unemployed moved from the South to the industrializing northwestern regions. We analysed mortalitytemperature relationships among residents died in a northern city, during 1980-1989, by birth-area groups: northern, middle, southern Italy. Methods: Since 1981, mortality data have been linked to census records as part of a longitudinal population study. Meteorological dataset was part of MISA study, the Italian meta-analysis on short term effects of air pollution on health. Log-linear models have been used to fit daily death count data as a function of different explanatory variables: months, weekdays, holiday, influenza epidemics, temperature and relative humidity. Results: Among residents died in the city 21% were born in the South, 8% in the middle and 71% in the North; the death’s daily means were respectively 4.5, 1.7 and 15.1. Elderly over 65 years were 68% among Southerners and about 78% among other groups. It’s likely that, in the eighties, some retired immigrants came back to native areas. Preliminary analyses confirm the V-shaped curve in each group. The curve for those born in the North shows two possible breakpoints approximately at 19°C and 25°C, while both curves for immigrants, born in the Middle or Southern Italy, show only one breakpoint (or MMT) at around 20°C. The left slope of each curve is substantially null, suggesting that the cold effect is negligible. At warmer temperatures, over the MMT, the slope is rather pronounced and steeper in the group of natives in northern areas; the percentage increase of mortality risk, for an increase of 1°C during hotter days, decreases with the latitude of the birth area: it is 6.9% (95%CL 4.2;9.7) for residents born in the North, while it is 4.0% (95%CL 1.9;6.1) for immigrants from Middle and 2.6% (95%CL 0.9;4.3) for those born in the South. Conclusions: This preliminary result confirms what already seen in the city of Milan, Lombardy, suggesting that heat tolerance in populations could be modulated by outdoor temperature experienced early in life, and no complete adaptation occurs if external environmental temperatures increase. Further analyses are on going, and will be resented, by age at migration and duration of residence, available in this data set
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