Assessing the effects of the Spanish partial smoking ban on cardiovascular and respiratory diseases: methodological issues

Abstract

ObjectiveRecent research has assessed the impact of tobacco laws on cardiovascular and respiratory morbidity. In this study, we also examined whether the association between the implementation of the 2005 Spanish smoking ban and hospital admissions for cardiovascular and respiratory diseases varies according to the adjustment for potential confounders.DesignEcological time series analysis.SettingResidents of Madrid and Barcelona cities (Spain).OutcomeData on daily emergency room admissions for acute myocardial infarction, cerebrovascular disease, chronic obstructive pulmonary disease (COPD), and asthma derived from the 2003–2006 Spanish hospital admissions registry.MethodsChanges in admission rates between 2006 and the 2003–2005 period were estimated using additive Poisson models allowing for overdispersion adjusted for secular trend in admission, seasonality, day of the week, temperature, number of flu and acute respiratory infection cases, pollution levels, tobacco consumption prevalence and, for asthma cases, pollen count.ResultsIn Madrid, fully adjusted models failed to detect significant changes in hospital admission rates for any disease during the study period. In Barcelona, however, hospital admissions decreased by 10.2% (95% CI 3.8% to 16.1%) for cerebrovascular diseases and by 16.0% (95% CI 7.0% to 24.1%) for COPD. Substantial changes in effect estimates were observed on adjustment for linear or quadratic trend. Effect estimates for asthma-related admissions varied substantially when adjusting for pollen count in Madrid, and for seasonality and tobacco consumption in Barcelona.ConclusionsOur results confirm that the potential impact of a smoking ban must be adjusted for the underlying secular trend. In asthma-related admissions, pollen count, seasonality and tobacco consumption must be specified in the model. The substantial variability in effects detected between the two cities of Madrid and Barcelona lends strong support for a nationwide study to assess the overall effect of a smoking ban in Spain and identify the causes of the observed heterogeneity.

Lower incidence of myocardial infarction after smoke-free legislation enforcement in Chile

“…Most studies of the impact of smoke-free legislation on the incidence of myocardial infarction have relied solely upon data on hospitalizations, 15 – 17 , 19 , 27 – 29 , 35 – 37 , 40 , 44 – 47 although some have analysed mortality data, either alone or with hospitalization data. 38 , 39 , 48 Here, we employed a population-based approach, combining both hospitalization and mortality data.…”

“…This strategy avoids many of the pitfalls of before-and-after study designs, particularly their limited capacity to take into account other confounding influences that could concurrently affect the myocardial infarction rate, such as changes in public policy and environmental factors. 17 Because of evidence that smoke-free legislation may also reduce the incidence of cerebrovascular accidents and that coronary and ischaemic cerebrovascular diseases share some pathological mechanisms, 18 , 19 we repeated the analysis for ischaemic stroke. In addition, following other studies that employed diagnostic controls, 19 we repeated our analysis for degenerative disc diseases and colon cancer.…”

Changes in hospitalizations for chronic respiratory diseases after two successive smoking bans in Spain

“…Based on previous work [ 29 ], all Poisson models were adjusted for the same confounders in all provinces and included harmonic terms for seasonality in admission rates, indicators for the day of the week, and smoothed functions of temperature, influenza epidemic status, and acute respiratory infection rates. Models for asthma admissions also included smoothed functions of pollen counts.…”

Longitudinal Associations of Smoke-Free Policies and Incident Cardiovascular Disease

“…These findings complement an existing body of literature that has generally indicated that smoke-free policy implementation is associated with lower rates of hospital admissions or mortality for cardiovascular disease. 16,17,[19][20][21][22][27][28][29][30][31][32][33][34][35] Prior studies have typically been ecological in nature [14][15][16][17][18][19][20][22][23][24][25][26][27][28][29][30][31][34][35][36] and have not had access to detailed individual-level information on sociodemographic characteristics and cardiovascular disease risk factors. Our findings that patterns were largely similar after controlling for a large number of potential confounders suggest that differences in cardiovascular disease risk among those in areas with and without smoke-free policies are not explained by differences in individual sociodemographics or traditional cardiovascular disease risk factors.…”

“…Prior studies have used primarily ecological designs, [14][15][16][17][18][19][20][22][23][24][25][26][27][28][29][30][31][34][35][36] and have lacked access to detailed individual-level data on sociodemographic characteristics and cardiovascular disease risk factors. Interpretation of results from ecological studies is limited by the potential for unmeasured confounding by individuallevel characteristics, a drawback that could be reduced by using data from ongoing cohort studies.…”