Analysis of common methodological flaws in the highest cited e-cigarette epidemiology research
Authors: Hajat Cother , Stein Emma , Selya Arielle , Polosa Riccardo ,   The CoEHAR study group, Alaimo Salvatore , Anfuso Carmelina Daniela , Barbagallo Ignazio , Basile Francesco , Battiato Sebastiano , Benhamou Brahim , Bertino Gaetano , Bianchi Alberto , Biondi Antonio G , Brandi Maria Luisa , Cacciola Emma , Cacciola Rossella R , Cacopardo Bruno Santi , Calogero Aldo E , Cambria Maria Teresa , Campagna Davide , Caraci Filippo , Cariola Agatino , Caruso Massimo , Caponnetto Pasquale , Ciancio Adriana , Cibella Fabio , Mauro Maurizio di , Piazza Jennifer di , Stefano Adriana di , Drago Filippo , Failla Salvatore , Faraci Rosario , Ferlito Salvatore , Ferrante Margherita , Ferro Alfredo , Ferro Giancarlo A , Frasca Francesco , Frittitta Lucia , Furneri Pio M , Gagliano Antonio , Gallo Giovanni , Galvano Fabio , Grasso Giuseppe , Guarino Francesca , Gulino Antonino , Jannini Emmanuele A , Vignera Sandro La , Lazzarino Giuseppe , Ledda Caterina , Leonardi Rosalia Maria , Volti Giovanni Li , Longo Antonio , Lupo Gabriella , Malerba Mario , Marletta Luigi , Nicolosi Guido , Nocera Francesco , Conti Gea Oliveri , Palazzo Giuseppe , Parenti Rosalba , Pedullà Eugenio , Pulvirenti Alfredo , Purrello Francesco , Rapisarda Francesco , Rapisarda Venerando , Rizzo Renata , Ronsisvalle Simone , Ronsisvalle Giuseppe , Ruggieri Martino , Santagati Maria C , Satriano Cristina , Sciacca Laura , Signorelli Maria Salvina , Tatullo Marco , Tibullo Daniele , Tomaselli Venera , Volarevic Vladislav , Zanoli Luca , Zappalà Agata 
Published: March 2022

The prevalence of vaping, also known as using e-cigarettes, vapes and vape pens, has prompted a demand for reliable, evidence-based research. However, published literature on the topic of vaping often raises concerns, characterized by serious flaws and a failure to adhere to accepted scientific methodologies. In this narrative review, we analyze popular vaping studies published in medical journals that purport to evaluate the association of vaping and smoking cessation, smoking initiation or health outcomes. We analyzed 24 included studies to identify the questions they claimed to address, stated methods, manner of implementation, discussions, and stated conclusions. After critical appraisal, we noted a multiplicity of flaws in these studies, and identified patterns as to the nature of such flaws. Many studies lacked a clear hypothesis statement: to the extent that a hypothesis could be inferred, the methods were not tailored to address the question of interest. Moreover, main outcome measures were poorly identified, and data analysis was further complicated by failure to control for confounding factors. The body of literature on “gateway” theory for the initiation of smoking was particularly unreliable. Overall, the results and discussion contained numerous unreliable assertions due to poor methods, including data collection that lacked relevance, and assertions that were unfounded. Many researchers claimed to find a causal association while not supporting such findings with meaningful data: the discussions and conclusions of such studies were, therefore, misleading. Herein, we identify the common flaws in the study design, methodology, and implementation found in published vaping studies. We present our summary recommendations for future vaping research. Our aim is to prompt future researchers to adhere to scientific methods to produce more reliable findings and conclusions in the field of vaping research.