Imperial College London

DrMonicaPirani

Faculty of MedicineSchool of Public Health

Lecturer in Biostatistics
 
 
 
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Contact

 

+44 (0)20 7594 1177monica.pirani

 
 
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Location

 

526Norfolk PlaceSt Mary's Campus

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Summary

 

Publications

Publication Type
Year
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17 results found

Pirani M, Mason A, Hansell A, Richardson S, Blangiardo Met al., 2020, A flexible hierarchical framework for improving inference in area-referenced environmental health studies, Biometrical Journal: journal of mathematical methods in biosciences, ISSN: 0323-3847

Study designs where data have been aggregated by geographical areas are popular in environmental epi-demiology. These studies are commonly based on administrative databases and, providing a completespatial coverage, are particularly appealing to make inference on the entire population. However, the re-sulting estimates are often biased and difficult to interpret due to unmeasured confounders, which typicallyare not available from routinely collected data. We propose a framework to improve inference drawn fromsuch studies exploiting information derived from individual-level survey data. The latter are summarized inan area-level scalar score by mimicking at ecological-level the well-known propensity score methodology.The literature on propensity score for confounding adjustment is mainly based on individual-level studiesand assumes a binary exposure variable. Here we generalize its use to cope with area-referenced stud-ies characterized by a continuous exposure. Our approach is based upon Bayesian hierarchical structuresspecified into a two-stage design: (i) geolocated individual-level data from survey samples are up-scaled atecological-level, then the latter are used to estimate a generalizedecological propensity score(EPS) in thein-sample areas; (ii) the generalized EPS is imputed in the out-of-sample areas under different assumptionsabout the missingness mechanisms, then it is included into the ecological regression, linking the exposureof interest to the health outcome. This delivers area-level risk estimates which allow a fuller adjustment forconfounding than traditional areal studies. The methodology is illustrated by using simulations and a casestudy investigating the risk of lung cancer mortality associated with nitrogen dioxide in England (UK).

Journal article

Wang Y, Pirani M, Hansell A, Richardson S, Blangiardo MAGet al., 2019, Using ecological propensity score to adjust for missing confounders in small area studies, Biostatistics, Vol: 20, Pages: 1-16, ISSN: 1465-4644

Small area ecological studies are commonly used in epidemiology to assess the impact of area level risk factors on health outcomes when data are only available in an aggregated form. However, the resulting estimates are often biased due to unmeasured confounders, which typically are not available from the standard administrative registries used for these studies. Extra information on confounders can be provided through external data sets such as surveys or cohorts, where the data are available at the individual level rather than at the area level; however, such data typically lack the geographical coverage of administrative registries. We develop a framework of analysis which combines ecological and individual level data from different sources to provide an adjusted estimate of area level risk factors which is less biased. Our method (i) summarizes all available individual level confounders into an area level scalar variable, which we call ecological propensity score (EPS), (ii) implements a hierarchical structured approach to impute the values of EPS whenever they are missing, and (iii) includes the estimated and imputed EPS into the ecological regression linking the risk factors to the health outcome. Through a simulation study, we show that integrating individual level data into small area analyses via EPS is a promising method to reduce the bias intrinsic in ecological studies due to unmeasured confounders; we also apply the method to a real case study to evaluate the effect of air pollution on coronary heart disease hospital admissions in Greater London.

Journal article

Blangiardo M, Pirani M, Kanapka L, Hansell A, Fuller Get al., 2019, A hierarchical modelling approach to assess multi pollutant effects in time-series studies, PL o S One, Vol: 14, ISSN: 1932-6203

When assessing the short-term effect of air pollution on health outcomes, it is common practice to consider one pollutant at a time, due to their high correlation. Multi pollutant methods have been recently proposed, mainly consisting of collapsing the different pollutants into air quality indexes or clustering the pollutants and then evaluating the effect of each cluster on the health outcome. A major drawback of such approaches is that it is not possible to evaluate the health impact of each pollutant. In this paper we propose the use of the Bayesian hierarchical framework to deal with multi pollutant concentrations in a two-component model: a pollutant model is specified to estimate the 'true' concentration values for each pollutant and then such concentration is linked to the health outcomes in a time-series perspective. Through a simulation study we evaluate the model performance and we apply the modelling framework to investigate the effect of six pollutants on cardiovascular mortality in Greater London in 2011-2012.

Journal article

Pirani M, Panton A, Purdie DA, Sahu SKet al., 2016, Modelling macronutrient dynamics in the Hampshire Avon river: a Bayesian approach to estimate seasonal variability and total flux, Science of the Total Environment, Vol: 572, Pages: 1449-1460, ISSN: 0048-9697

The macronutrients nitrate and phosphate are aquatic pollutants that arise naturally, however, in excess concentrations they can be harmful to human health and ecosystems. These pollutants are driven by river currents and show dynamics that are affected by weather patterns and extreme rainfall events. As a result, the nutrient budget in the receiving estuaries and coasts can change suddenly and seasonally, causing ecological damage to resident wildlife and fish populations. In this paper, we propose a statistical change-point model with interactions between time and river flow, to capture the macronutrient dynamics and their responses to river flow threshold behaviour. It also accounts for the nonlinear effect of water quality properties via nonparametric penalised splines. This model enables us to estimate the daily levels of riverine macronutrient fluxes and their seasonal and annual totals. In particular, we present a study of macronutrient dynamics on the Hampshire Avon River, which flows to the southern coast of the UK through the Christchurch Harbour estuary. We model daily data for more than a year during 2013-14 in which period there were multiple severe meteorological conditions leading to localised flooding. Adopting a Bayesian inference framework, we have quantified riverine macronutrient fluxes based on input river flow values. Out of sample empirical validation methods justify our approach, which captures also the dependencies of macronutrient concentrations with water body characteristics.

Journal article

Morandi G, Periche Tomas E, Pirani M, 2016, Mortality risk in alcoholic patients in northern Italy: comorbidity and treatment retention effects in a 30-year follow-up study, Alcohol and Alcoholism, Vol: 51, Pages: 63-70, ISSN: 1464-3502

Aims To analyse the general and cause-specific mortality over the course of 30 years among subjects treated for alcohol use disorders (AUD) in Northern Italy.Methods Cohort of 2499 subjects followed-up for mortality until 31 December 2012. Standardized mortality ratios (SMRs) and 95% confidence intervals (CI) were computed to compare the mortality in the cohort with the general population. Cox regression was used to study the effect of psychiatric disorders, burden of physical comorbidity and retention in treatment on mortality, controlling for socio-demographic factors.Results During the follow-up, 435 deaths occurred. Compared with the general population, alcoholics experienced a 5-fold increased mortality (SMR: 5.53; 95% CI: 5.03, 6.07). Significant excess mortality was observed for a range of specific causes: infections, cancers, cardiovascular, respiratory and digestive system diseases as well as violent causes. In multivariate analysis, the hazard of dying was lower for female gender (hazard ratio [HR]: 0.62; 95% CI: 0.46, 0.84) and for increasing length of retention in treatment (HR for third tertile vs first tertile: 0.43; 95% CI: 0.32, 0.57). Burden of physical comorbidity was associated with increased hazard of dying (HR for 3+ comorbidities vs no comorbidities: 4.40; 95% CI: 2.91, 6.66). Psychiatric comorbidity was not associated with mortality.Conclusions Despite the harmful effect of AUD, retention in treatment represented a protective factor against death, suggesting that strategies supporting primary medical- and social-care may effectively reduce premature mortality.

Journal article

Pirani M, Best N, Blangiardo M, Liverani S, Atkinson RW, Fuller GWet al., 2015, Analysing the health effects of simultaneous exposure to physical and chemical properties of airborne particles, Environment International, Vol: 79, Pages: 56-64, ISSN: 0160-4120

Background:Airborne particles are a complex mix of organic and inorganic compounds, with a range of physical and chemical properties. Estimation of how simultaneous exposure to air particles affects the risk of adverse health response represents a challenge for scientific research and air quality management. In this paper, we present a Bayesian approach that can tackle this problem within the framework of time series analysis.Methods:We used Dirichlet process mixture models to cluster time points with similar multipollutant and response profiles, while adjusting for seasonal cycles, trends and temporal components. Inference was carried out via Markov Chain Monte Carlo methods. We illustrated our approach using daily data of a range of particle metrics and respiratory mortality for London (UK) 2002–2005. To better quantify the average health impact of these particles, we measured the same set of metrics in 2012, and we computed and compared the posterior predictive distributions of mortality under the exposure scenario in 2012 vs 2005.Results:The model resulted in a partition of the days into three clusters. We found a relative risk of 1.02 (95% credible intervals (CI): 1.00, 1.04) for respiratory mortality associated with days characterised by high posterior estimates of non-primary particles, especially nitrate and sulphate. We found a consistent reduction in the airborne particles in 2012 vs 2005 and the analysis of the posterior predictive distributions of respiratory mortality suggested an average annual decrease of − 3.5% (95% CI: − 0.12%, − 5.74%).Conclusions:We proposed an effective approach that enabled the better understanding of hidden structures in multipollutant health effects within time series analysis. It allowed the identification of exposure metrics associated with respiratory mortality and provided a tool to assess the changes in health effects from various policies to control the ambient particle matter mixtures.

Journal article

Alpaca RIP, Forastiere F, Pirani M, 2013, Low exposure to lead and reproductive health: a cohort study of female workers in the ceramic industry of Emilia-Romagna (Northern Italy), EPIDEMIOLOGIA & PREVENZIONE, Vol: 37, Pages: 367-375, ISSN: 1120-9763

Journal article

Pirani M, Gulliver J, Fuller G, Blangiardo Met al., 2013, Bayesian spatiotemporal modelling for the assessment of short-term exposure to particle pollution in urban areas, Journal of exposure science & environmental epidemiology, Vol: N/A, ISSN: 1559-064X

This paper describes a Bayesian hierarchical approach to predict short-term concentrations of particle pollution in an urban environment, with application to inhalable particulate matter (PM10) in Greater London. We developed and compared several spatiotemporal models that differently accounted for factors affecting the spatiotemporal properties of particle concentrations. We considered two main source contributions to ambient measurements: (i) the long-range transport of the secondary fraction of particles, which temporal variability was described by a latent variable derived from rural concentrations; and (ii) the local primary component of particles (traffic- and non-traffic-related) captured by the output of the dispersion model ADMS-Urban, which site-specific effect was described by a Bayesian kriging. We also assessed the effect of spatiotemporal covariates, including type of site, daily temperature to describe the seasonal changes in chemical processes affecting local PM10 concentrations that are not considered in local-scale dispersion models and day of the week to account for time-varying emission rates not available in emissions inventories. The evaluation of the predictive ability of the models, obtained via a cross-validation approach, revealed that concentration estimates in urban areas benefit from combining the city-scale particle component and the long-range transport component with covariates that account for the residual spatiotemporal variation in the pollution process.

Journal article

Pirani M, Marcheselli R, Marcheselli L, Bari A, Federico M, Sacchi Set al., 2011, Risk for second malignancies in non-Hodgkin's lymphoma survivors: a meta-analysis, ANNALS OF ONCOLOGY, Vol: 22, Pages: 1845-1858, ISSN: 0923-7534

Journal article

El Mistiri M, Pirani M, El Sahli N, El Mangoush M, Attia A, Shembesh R, Habel S, El Homry F, Hamad S, Federico Met al., 2010, Cancer profile in Eastern Libya: incidence and mortality in the year 2004, ANNALS OF ONCOLOGY, Vol: 21, Pages: 1924-1925, ISSN: 0923-7534

Journal article

Federico M, Pirani M, Rashid I, Caranci N, Cirilli Cet al., 2010, Cancer incidence in people with residential exposure to a municipal waste incinerator: An ecological study in Modena (Italy), 1991-2005, WASTE MANAGEMENT, Vol: 30, Pages: 1362-1370, ISSN: 0956-053X

Journal article

Agabiti N, Pirani M, Schifano P, Cesaroni G, Davoli M, Bisanti L, Caranci N, Costa G, Forastiere F, Marinacci C, Russo A, Spadea T, Perucci CAet al., 2009, Income level and chronic ambulatory care sensitive conditions in adults: a multicity population-based study in Italy, BMC PUBLIC HEALTH, Vol: 9

Journal article

Sacchi S, Pirani M, Marcheselli L, Marcheselli R, Bari A, Cirilli C, Massimo Fet al., 2009, Second Malignancy After Treatment for Non-Hodgkin Lymphoma: a Systematic Review and a Meta-Analysis of Population-Based and Cohort Studies, 51st Annual Meeting of the American-Society-of-Hematology, Publisher: AMER SOC HEMATOLOGY, Pages: 761-761, ISSN: 0006-4971

Conference paper

Ferretti S, Guzzinati S, Zambon P, Manneschi G, Crocetti E, Falcini F, Giorgetti S, Cirilli C, Pirani M, Mangone L, Di Felice E, Del Lisi V, Sgargi P, Buzzoni C, Russo A, Paci Eet al., 2009, Cancer incidence estimation by hospital discharge flow as compared with cancer registries data, EPIDEMIOLOGIA & PREVENZIONE, Vol: 33, Pages: 147-153, ISSN: 1120-9763

Journal article

Gerra G, Bertacca S, Zaimovic A, Pirani M, Branchi B, Ferri Met al., 2008, Relationship of personality traits and drug of choice by cocaine addicts and heroin addicts, SUBSTANCE USE & MISUSE, Vol: 43, Pages: 317-330, ISSN: 1082-6084

Journal article

Pirani M, Schifano P, Agabiti N, Davoli M, Caranci N, Perucci CAet al., 2006, [Potentially avoidable hospitalisation in Bologna, 1997-2000: temporal trend and differences by income level]., Epidemiol Prev, Vol: 30, Pages: 169-177, ISSN: 1120-9763

OBJECTIVE: To describe the temporal trend of hospitalisations for Ambulatory Care Sensitive Conditions (ACSCs) from 1997 to 2000 in Bologna (Italy) and to analyze the association with the income level. DESIGN AND SETTING: We have selected two panels of ACSCs: eight conditions for the paediatric/young population (<20 years of age) and fourteen for the adult population (> or =20 years of age). All discharges for ACSCs of residents in Bologna from Emilia-Romagna hospitals have been selected in the years 1997-2000. An indicator of social position was computed: the median per capita equivalent income by census block, obtained through record linkage between the Italian Tax Register (income earned in 1998) and the Population Register of Bologna. MAIN OUTCOME MEASURES: The direct age-standardized rates and the rate ratio by income level have been calculated. The Poisson regression model has been used to calculate the relative risk (RR) of hospitalizations for ACSCs. RESULTS: 2359 (17.6% of the total) hospitalisations have been selected among the paediatric/young population and 27822 (11.1% of the total) among the adult population. The annual age-adjusted rate of ACSC is 122.68 per 10000 persons among children and 176.60 among adults. The hospitalisation forACSCs among children is associated with a middle-low level of income (RR 1.55; CI 95% 1.35-1.78 for the lowest level vs. highest level), male gender and age <5 years old. In the adult population the risk of hospitalisation for ACSCs is higher among those with lower levels of income (RR 1.80; CI 95% 1.66-1.95 for the lowest level vs. highest level), moreover the RR is higher for men at every age. The admissions forACSCs among adults show a decreasing temporal trend. CONCLUSIONS: The disadvantaged groups of the population experience the highest risk of hospitalisation for ACSCs, with differences by gender and age groups. Although it is difficult to specifically identify the mechanisms potentially involved in the re

Journal article

Antolini G, Pirani M, Morandi G, Sorio Cet al., 2006, [Gender difference and mortality in a cohort of heroin users in the Provinces of Modena and Ferrara, 1975-1999]., Epidemiol Prev, Vol: 30, Pages: 91-99, ISSN: 1120-9763

OBJECTIVE: To analyse overall and cause-specific hazards of death in a cohort of heroin users, separately by gender, survival and other risk factors. DESIGN AND SETTING: Longitudinal study of intravenous heroin users; subjects were enrolled between 1975 and 1999 in public health services of the Provinces of Modena and Ferrara and were included in a treatment program. MAIN OUTCOME MEASURES: For each gender, age-standardized mortality rates and standardized mortality ratios (SMR) for all causes and for specific causes. Kaplan-Meier method was used for estimating survival probability and Cox regression model to estimate hazard ratios (HR) of death. RESULTS: in the cohort of 4.644 intravenous drug users, 801 deaths were observed. In both sexes, mortality due to AIDS was lower in subjects enrolled in 1990-99 than among those enrolled in 1980-89. Mortality caused by overdose was particularly high in males enrolled between 1995-99. (SMRs in males and females were respectively 12.12 (95% CI 11.22-13.08) and 20.26 (17.23-23.83). Survival probability at 20 years of observation was 62% (60% for males and 68% for females). Risk of death was highest in males, in subjects enrolled after age 25, in subjects with a low educational level and in unemployed persons. CONCLUSION: Gender and socioeconomic conditions are important determinants of mortality among heroin users. The increase in deaths from heroin overdose in subjects enrolled in the recent years requires particular attention.

Journal article

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