Spatial Bayesian distributed lag non-linear models (SB-DLNM) for small-area exposure-lag-response epidemiological modelling.

BACKGROUND: Distributed lag non-linear models (DLNMs) are the reference framework for modelling lagged non-linear associations. They are usually used in large-scale multi-location studies. Attempts to study these associations in small areas either did not include the lagged non-linear effects, did not allow for geographically-varying risks or downscaled risks from larger spatial units through socioeconomic and physical meta-predictors when the estimation of the risks was not feasible due to low statistical power. METHODS: Here we proposed spatial Bayesian DLNMs (SB-DLNMs) as a new framework for the estimation of reliable small-area lagged non-linear associations, and demonstrated the methodology for the case study of the temperature-mortality relationship in the 73 neighbourhoods of the city of Barcelona. We generalized location-independent DLNMs to the Bayesian framework (B-DLNMs), and extended them to SB-DLNMs by incorporating spatial models in a single-stage approach that accounts for the spatial dependence between risks. RESULTS: The results of the case study highlighted the benefits of incorporating the spatial component for small-area analysis. Estimates obtained from independent B-DLNMs were unstable and unreliable, particularly in neighbourhoods with very low numbers of deaths. SB-DLNMs addressed these instabilities by incorporating spatial dependencies, resulting in more plausible and coherent estimates and revealing hidden spatial patterns. In addition, the Bayesian framework enriches the range of estimates and tests that can be used in both large- and small-area studies. CONCLUSIONS: SB-DLNMs account for spatial structures in the risk associations across small areas. By modelling spatial differences, SB-DLNMs facilitate the direct estimation of non-linear exposure-response lagged associations at the small-area level, even in areas with as few as 19 deaths. The manuscript includes an illustrative code to reproduce the results, and to facilitate the implementation of other case studies by other researchers.

Spatio-temporal small area surveillance of the COVID-19 pandemic.

The emergence of COVID-19 requires new effective tools for epidemiological surveillance. Spatio-temporal disease mapping models, which allow dealing with small units of analysis, are a priority in this context. These models provide geographically detailed and temporally updated overviews of the current state of the pandemic, making public health interventions more effective. These models also allow estimating epidemiological indicators highly demanded for COVID-19 surveillance, such as the instantaneous reproduction number R t , even for small areas. In this paper, we propose a new spatio-temporal spline model particularly suited for COVID-19 surveillance, which allows estimating and monitoring R t for small areas. We illustrate our proposal on the study of the disease pandemic in two Spanish regions. As a result, we show how tourism flows have shaped the spatial distribution of the disease in these regions. In these case studies, we also develop new epidemiological tools to be used by regional public health services for small area surveillance.

Geographical Variability in Mortality in Urban Areas: A Joint Analysis of 16 Causes of Death.

The geographical distribution of mortality has frequently been studied. Nevertheless, those studies often consider isolated causes of death. In this work, we aim to study the geographical distribution of mortality in urban areas, in particular, in 26 Spanish cities. We perform an overall study of 16 causes of death, considering that their geographical patterns could be dependent and estimating the dependence between the causes of death. We study the deaths in these 26 cities during the period 1996-2015 at the census tract level. A multivariate disease mapping model is used in order to solve the potential small area estimation problems that these data could show. We find that most of the geographical patterns found show positive correlations. This suggests the existence of a transversal geographical pattern, common to most causes of deaths, which determines those patterns to a higher/lower extent depending on each disease. The causes of death that exhibit that underlying pattern in a more prominent manner are chronic obstructive pulmonary disease (COPD), lung cancer, and cirrhosis for men and cardiovascular diseases and dementias for women. Such findings are quite consistent for most of the cities in the study. The high positive correlation found between geographical patterns reflects the existence of both high and low-risk areas in urban settings, in general terms for nearly all the causes of death. Moreover, the high-risk areas found often coincide with neighborhoods known for their high deprivation. Our results suggest that dependence among causes of death is a key aspect to be taken into account when mapping mortality, at least in urban contexts.

Socioeconomic Inequalities in Mortality among Foreign-Born and Spanish-Born in Small Areas in Cities of the Mediterranean Coast in Spain, 2009-2015.

Many studies have analysed socioeconomic inequalities and its association with mortality in urban areas. However, few of them have differentiated between native and immigrant populations. This study is an ecological study of mortality by overall mortality and analyses the inequalities in mortality in these populations according to the level of deprivation in small areas of large cities in the Valencian Community, from 2009 to 2015. The census tract was classified into five deprivation levels using an index based on socioeconomic indicators from the 2011 census. Rates and relative risks of death were calculated by sex, age, level of deprivation and country of birth. Poisson regression models have been used. In general, there was a higher risk of death in natives at the levels of greatest deprivation, which did not happen in immigrants. During the 2009-2015 period, there were socioeconomic inequalities in mortality, particularly in natives, who presented a higher risk of death than immigrants. Future interventions and social policies should be implemented in order to reduce inequalities in mortality amongst socioeconomic levels and to maintain the advantage that the immigrant population enjoys.

Some findings on zero-inflated and hurdle poisson models for disease mapping.

Zero excess in the study of geographically referenced mortality data sets has been the focus of considerable attention in the literature, with zero-inflation being the most common procedure to handle this lack of fit. Although hurdle models have also been used in disease mapping studies, their use is more rare. We show in this paper that models using particular treatments of zero excesses are often required for achieving appropriate fits in regular mortality studies since, otherwise, geographical units with low expected counts are oversmoothed. However, as also shown, an indiscriminate treatment of zero excess may be unnecessary and has a problematic implementation. In this regard, we find that naive zero-inflation and hurdle models, without an explicit modeling of the probabilities of zeroes, do not fix zero excesses problems well enough and are clearly unsatisfactory. Results sharply suggest the need for an explicit modeling of the probabilities that should vary across areal units. Unfortunately, these more flexible modeling strategies can easily lead to improper posterior distributions as we prove in several theoretical results. Those procedures have been repeatedly used in the disease mapping literature, and one should bear these issues in mind in order to propose valid models. We finally propose several valid modeling alternatives according to the results mentioned that are suitable for fitting zero excesses. We show that those proposals fix zero excesses problems and correct the mentioned oversmoothing of risks in low populated units depicting geographic patterns more suited to the data.

Towards a Multidimensional Approach to Bayesian Disease Mapping.

Multivariate disease mapping enriches traditional disease mapping studies by analysing several diseases jointly. This yields improved estimates of the geographical distribution of risk from the diseases by enabling borrowing of information across diseases. Beyond multivariate smoothing for several diseases, several other variables, such as sex, age group, race, time period, and so on, could also be jointly considered to derive multivariate estimates. The resulting multivariate structures should induce an appropriate covariance model for the data. In this paper, we introduce a formal framework for the analysis of multivariate data arising from the combination of more than two variables (geographical units and at least two more variables), what we have called Multidimensional Disease Mapping. We develop a theoretical framework containing both separable and non-separable dependence structures and illustrate its performance on the study of real mortality data in Comunitat Valenciana (Spain).

Trends in socioeconomic inequalities in mortality in small areas of 33 Spanish cities.

BACKGROUND: In Spain, several ecological studies have analyzed trends in socioeconomic inequalities in mortality from all causes in urban areas over time. However, the results of these studies are quite heterogeneous finding, in general, that inequalities decreased, or remained stable. Therefore, the objectives of this study are: (1) to identify trends in geographical inequalities in all-cause mortality in the census tracts of 33 Spanish cities between the two periods 1996-1998 and 2005-2007; (2) to analyse trends in the relationship between these geographical inequalities and socioeconomic deprivation; and (3) to obtain an overall measure which summarises the relationship found in each one of the cities and to analyse its variation over time. METHODS: Ecological study of trends with 2 cross-sectional cuts, corresponding to two periods of analysis: 1996-1998 and 2005-2007. Units of analysis were census tracts of the 33 Spanish cities. A deprivation index calculated for each census tracts in all cities was included as a covariate. A Bayesian hierarchical model was used to estimate smoothed Standardized Mortality Ratios (sSMR) by each census tract and period. The geographical distribution of these sSMR was represented using maps of septiles. In addition, two different Bayesian hierarchical models were used to measure the association between all-cause mortality and the deprivation index in each city and period, and by sex: (1) including the association as a fixed effect for each city; (2) including the association as random effects. In both models the data spatial structure can be controlled within each city. The association in each city was measured using relative risks (RR) and their 95 % credible intervals (95 % CI). RESULTS: For most cities and in both sexes, mortality rates decline over time. For women, the mortality and deprivation patterns are similar in the first period, while in the second they are different for most cities. For men, RRs remain stable over time in 29 cities, in 3 diminish and in 1 increase. For women, in 30 cities, a non-significant change over time in RR is observed. However, in 4 cities RR diminishes. In overall terms, inequalities decrease (with a probability of 0.9) in both men (RR = 1.13, 95 % CI = 1.12-1.15 in the 1st period; RR = 1.11, 95 % CI = 1.09-1.13 in the 2nd period) and women (RR = 1.07, 95 % CI = 1.05-1.08 in the 1st period; RR = 1.04, 95 % CI = 1.02-1.06 in the 2nd period). CONCLUSIONS: In the future, it is important to conduct further trend studies, allowing to monitoring trends in socioeconomic inequalities in mortality and to identify (among other things) temporal factors that may influence these inequalities.

Accesibilidad a los datos de investigación en salud pública: eficiencia y reproducibilidad versusconfidencialidad / Access to public health research data: efficiency and reproducibility versus confidentiality

No disponible

Effectiveness of rotavirus vaccines, licensed but not funded, against rotavirus hospitalizations in the Valencia Region, Spain.

BACKGROUND: Although rotavirus vaccines have been licensed in Spain for over 8 years, they are not funded by its public health systems. The analysis of their effectiveness in the Valencia Region could better inform decisions about potential inclusion in the official immunization schedule. Our aim was to assess the effectiveness of Rotarix® (RV1) and RotaTeq® (RV5) against rotavirus hospitalizations. METHODS: We conducted a retrospective cohort study using the region's health care databases, among resident children aged <3 years covered by the National Health System, during January 2007-June 2012. We compared two cohorts of vaccinated children: the first included children who received at least one dose of a rotavirus vaccine, and the second included children who were not vaccinated with rotavirus vaccines but received at least one dose of a pneumococcal vaccine, another licensed but non-funded vaccine. The main outcome was rotavirus hospitalization, either laboratory-confirmed (confirmed) or codified as rotavirus (probable). Rotavirus vaccine effectiveness (RVE) by vaccine brand was assessed using Cox proportional hazards models. RESULTS: The study included 78,281 rotavirus and 96,643 pneumococcal vaccinees. Adjusted RVE against probable or confirmed rotavirus hospitalizations was 86% (95% CI: 78-91%) and 88% (95% CI: 81-92%) for a complete series of RV1 and RV5 respectively. CONCLUSIONS: Both rotavirus vaccines were over 85% effective against rotavirus hospitalization among young children. The high effectiveness shown argues in favor of their inclusion in the official schedule. Additional information on rotavirus vaccine safety, duration of protection, and benefit-risk will also be needed to inform such deliberations.

Trends in socioeconomic inequalities in ischemic heart disease mortality in small areas of nine Spanish cities from 1996 to 2007 using smoothed ANOVA.

The aim of this study was to analyze the evolution of socioeconomic inequalities in mortality due to ischemic heart diseases (IHD) in the census tracts of nine Spanish cities between the periods 1996-2001 and 2002-2007. Among women, there are socioeconomic inequalities in IHD mortality in the first period which tended to remain stable or even increase in the second period in most of the cities. Among men, in general, no socioeconomic inequalities have been detected for this cause in either of the periods. These results highlight the importance of intra-urban inequalities in mortality due to IHD and their evolution over time.

Do socioeconomic inequalities in mortality vary between different Spanish cities? a pooled cross-sectional analysis.

BACKGROUND: The relationship between deprivation and mortality in urban settings is well established. This relationship has been found for several causes of death in Spanish cities in independent analyses (the MEDEA project). However, no joint analysis which pools the strength of this relationship across several cities has ever been undertaken. Such an analysis would determine, if appropriate, a joint relationship by linking the associations found. METHODS: A pooled cross-sectional analysis of the data from the MEDEA project has been carried out for each of the causes of death studied. Specifically, a meta-analysis has been carried out to pool the relative risks in eleven Spanish cities. Different deprivation-mortality relationships across the cities are considered in the analysis (fixed and random effects models). The size of the cities is also considered as a possible factor explaining differences between cities. RESULTS: Twenty studies have been carried out for different combinations of sex and causes of death. For nine of them (men: prostate cancer, diabetes, mental illnesses, Alzheimer's disease, cerebrovascular disease; women: diabetes, mental illnesses, respiratory diseases, cirrhosis) no differences were found between cities in the effect of deprivation on mortality; in four cases (men: respiratory diseases, all causes of mortality; women: breast cancer, Alzheimer's disease) differences not associated with the size of the city have been determined; in two cases (men: cirrhosis; women: lung cancer) differences strictly linked to the size of the city have been determined, and in five cases (men: lung cancer, ischaemic heart disease; women: ischaemic heart disease, cerebrovascular diseases, all causes of mortality) both kinds of differences have been found. Except for lung cancer in women, every significant relationship between deprivation and mortality goes in the same direction: deprivation increases mortality. Variability in the relative risks across cities was found for general mortality for both sexes. CONCLUSIONS: This study provides a general overview of the relationship between deprivation and mortality for a sample of large Spanish cities combined. This joint study allows the exploration of and, if appropriate, the quantification of the variability in that relationship for the set of cities considered.

Stroke mortality and trends from 1990 to 2006 in 39 countries from Europe and Central Asia: implications for control of high blood pressure.

AIMS: The aim of the present study was to extend our understanding of international trends in stroke and major sequelae in Europe and countries peripheral to Europe by assessing: (1) current mortality rates, (2) the most recent 15-year prevalence trends, and (3) the relationship between systolic blood pressure in community surveys and national stroke mortality. METHODS AND RESULTS: Data were obtained from the World Health Organization (WHO www.who.int/whosis/database/mort/table.cfm), and represent national vital statistics as reported by 39 countries (European and Central Asian countries) using a standard format and population-based cardiovascular surveys. Total numbers of deaths by stroke (International Classification of Diseases 430-438, 444) and the age, sex-adjusted incidence rates were obtained and grouped according to three standard demographic categories: A, B, and C (WHO). A Bayesian linear mixed effect model was fitted to the annual mortality rates. Higher rates of stroke mortality were observed for B and C group countries as compared with those countries belonging to Group A (e.g. Bulgaria 273.9 and 281.1; Israel 37.7 and 45.4 per 100 000 men and women, respectively). Even though the mortality rates within the country groupings were relatively similar, countries with marked deviation from the average were observed, mainly in Groups B and C. Stroke mortality decreased sharply in Group A during the period of study; conversely it had increased substantially in Group B and to a lesser extent in Group C. For both sexes markedly higher rates were noted moving from west to east, with some exceptions. CONCLUSION: We have entered a period of rapidly increasing international inequality in stroke risk, where countries with low adult mortality in the latter 20th century extended their downward trend and countries with moderate as well as high mortality have on average seen unprecedented increases in death rates from stroke.

Cancer mortality inequalities in urban areas: a Bayesian small area analysis in Spanish cities.

BACKGROUND: Intra-urban inequalities in mortality have been infrequently analysed in European contexts. The aim of the present study was to analyse patterns of cancer mortality and their relationship with socioeconomic deprivation in small areas in 11 Spanish cities. METHODS: It is a cross-sectional ecological design using mortality data (years 1996-2003). Units of analysis were the census tracts. A deprivation index was calculated for each census tract. In order to control the variability in estimating the risk of dying we used Bayesian models. We present the RR of the census tract with the highest deprivation vs. the census tract with the lowest deprivation. RESULTS: In the case of men, socioeconomic inequalities are observed in total cancer mortality in all cities, except in Castellon, Cordoba and Vigo, while Barcelona (RR = 1.53 95%CI 1.42-1.67), Madrid (RR = 1.57 95%CI 1.49-1.65) and Seville (RR = 1.53 95%CI 1.36-1.74) present the greatest inequalities. In general Barcelona and Madrid, present inequalities for most types of cancer. Among women for total cancer mortality, inequalities have only been found in Barcelona and Zaragoza. The excess number of cancer deaths due to socioeconomic deprivation was 16,413 for men and 1,142 for women. CONCLUSION: This study has analysed inequalities in cancer mortality in small areas of cities in Spain, not only relating this mortality with socioeconomic deprivation, but also calculating the excess mortality which may be attributed to such deprivation. This knowledge is particularly useful to determine which geographical areas in each city need intersectorial policies in order to promote a healthy environment.

A kernel-based spatio-temporal surveillance system for monitoring influenza-like illness incidence.

The threat of pandemics has made influenza surveillance systems a priority in epidemiology services around the world. The emergence of A-H1N1 influenza has required accurate surveillance systems in order to undertake specific actions only when and where they are necessary. In that sense, the main goal of this article is to describe a novel methodology for monitoring the geographical distribution of the incidence of influenza-like illness, as a proxy for influenza, based on information from sentinel networks. A Bayesian Poisson mixed linear model is proposed in order to describe the observed cases of influenza-like illness for every sentinel and week of surveillance. This model includes a spatio-temporal random effect that shares information in space by means of a kernel convolution process and in time by means of a first order autoregressive process. The extrapolation of this term to sites where information on incidence is not available will allow us to visualise the geographical distribution of the disease for every week of study. The following article shows the performance of this model in the Comunitat Valenciana's Sentinel Network (one of the 17 autonomous regions of Spain) as a real case study of this methodology.

Recourse to induced abortion in Spain: profiling of users and the influence of migrant populations

Background: Social vulnerability implies a higher risk of induced abortion (IA). Immigrant status could be an additional factor. The objective was to identify the patterns surrounding which women resort to IAs, and to study the relationship between socio-economic and health system factors. Another aim was to determine the relationship between the patterns identified and the immigrant's country. Methods: A cross-sectional study was performed including all IAs notified during 2006 on women residing in three Spanish autonomous communities (the Balearic Islands, Catalonia and Comunitat Valenciana). We used sociodemographic, nationality and related variables, reproductive history and use of health services. A Categorical Principal Component Analysis was used to summarize the information and to identify profiles. Results: More than a third of IAs were performed on non-Spanish women. Four dimensions have been determined that define the profile of women resorting to IAs: age, reproductive history and marital status; type of health services used; social level; and earlier or late IA and its repetitive use. Age and related factors were important determinants. Economic status and knowledge of the health system were related to access to contraception and IA information. Spanish, Western European and South American women had a higher social level than Romanian and African women. Late IA use and a lower recurrence characterised Asian, North African and Spanish women. Conclusion: Differences on IA use between groups of different women seem to be related to vulnerability (economic, social, knowledge and use of healthcare services). There is a different situation among immigrants of differing nationalities (AU)

Objetivos: La vulnerabilidad social representa un riesgo de interrupción voluntaria del embarazo (IVE). La inmigración puede ser un factor adicional. Se pretendía identificar patrones que caracterizaran a las mujeres que abortan y estudiar la relación con factores socioeconómicos y de atención sanitaria. Otro objetivo fue determinar la relación entre los patrones identificados y el origen de las inmigrantes. Métodos: Se realizó un estudio transversal incluyendo todas las IVE notificadas durante 2006 a tres registros de IVE de comunidades autónomas: Illes Balears, Catalunya y Comunitat Valenciana. Se utilizaron variables sociodemográficas, de nacionalidad y relacionadas, historia reproductiva y de utilización de servicios sanitarios. Se realizó un análisis de componentes principales categórico para resumir la información e identificar perfiles. Resultados: Las inmigrantes representaron más de un tercio de las IVE. Cuatro dimensiones definieron el perfil de las mujeres que abortan: edad, historia reproductiva y estado civil; utilización de servicios públicos o privados; nivel social; IVE tardía o precoz y su recurrencia. Edad y factores relacionados fueron determinantes importantes. El nivel económico y el conocimiento del sistema sanitario estaban relacionados con el acceso a la anticoncepción y a la información sobre IVE. Españolas, europeas occidentales y latinoamericanas tenían mayor nivel social que rumanas y africanas. El uso tardío de la IVE y una menor recurrencia fue característico de españolas, norteafricanas y asiáticas. Conclusión: Las diferencias en el recurso a la IVE entre grupos de mujeres parecen relacionarse con la vulnerabilidad (económica, social, de conocimiento y uso del sistema sanitario). La situación varía entre inmigrantes de diferentes nacionalidades (AU)

Recourse to induced abortion in Spain: profiling of users and the influence of migrant populations.

BACKGROUND: Social vulnerability implies a higher risk of induced abortion (IA). Immigrant status could be an additional factor. The objective was to identify the patterns surrounding which women resort to IAs, and to study the relationship between socio-economic and health system factors. Another aim was to determine the relationship between the patterns identified and the immigrant's country. METHODS: A cross-sectional study was performed including all IAs notified during 2006 on women residing in three Spanish autonomous communities (the Balearic Islands, Catalonia and Comunitat Valenciana). We used sociodemographic, nationality and related variables, reproductive history and use of health services. A Categorical Principal Component Analysis was used to summarize the information and to identify profiles. RESULTS: More than a third of IAs were performed on non-Spanish women. Four dimensions have been determined that define the profile of women resorting to IAs: age, reproductive history and marital status; type of health services used; social level; and earlier or late IA and its repetitive use. Age and related factors were important determinants. Economic status and knowledge of the health system were related to access to contraception and IA information. Spanish, Western European and South American women had a higher social level than Romanian and African women. Late IA use and a lower recurrence characterised Asian, North African and Spanish women. CONCLUSION: Differences on IA use between groups of different women seem to be related to vulnerability (economic, social, knowledge and use of healthcare services). There is a different situation among immigrants of differing nationalities.

Preventable avoidable mortality: evolution of socioeconomic inequalities in urban areas in Spain, 1996-2003.

This study describes the inequalities in preventable avoidable mortality in relation to socioeconomic levels and analyses their evolution during the period 1996-2003 in the cities of Alicante, Castellon and Valencia. Four causes of preventable avoidable mortality were analysed according to sex: malignant tumour of the trachea, bronchus and lung, cirrhosis and other chronic diseases of the liver, motor vehicle accidents and AIDS, which had caused the death of non-institutionalised residents in the three cities during the period 1996-2003. The different census tracts were grouped into three socioeconomic levels. In general, socioeconomic inequalities in preventable avoidable mortality remain constant in time, except the ones caused by AIDS in Valencia, where they increase for men. Some census tracts in the three cities where the study was carried out were found to have significantly higher preventable mortality rates, and therefore require intervention.

Bayesian Markov switching models for the early detection of influenza epidemics.

The early detection of outbreaks of diseases is one of the most challenging objectives of epidemiological surveillance systems. In this paper, a Markov switching model is introduced to determine the epidemic and non-epidemic periods from influenza surveillance data: the process of differenced incidence rates is modelled either with a first-order autoregressive process or with a Gaussian white-noise process depending on whether the system is in an epidemic or in a non-epidemic phase. The transition between phases of the disease is modelled as a Markovian process. Bayesian inference is carried out on the former model to detect influenza epidemics at the very moment of their onset. Moreover, the proposal provides the probability of being in an epidemic state at any given moment. In order to validate the methodology, a comparison of its performance with other alternatives has been made using influenza illness data obtained from the Sanitary Sentinel Network of the Comunitat Valenciana, one of the 17 autonomous regions in Spain.