Multitask group Lasso for Genome Wide association Studies in diverse populations.

Genome-Wide Association Studies, or GWAS, aim at finding Single Nucleotide Polymorphisms (SNPs) that are associated with a phenotype of interest. GWAS are known to suffer from the large dimensionality of the data with respect to the number of available samples. Other limiting factors include the dependency between SNPs, due to linkage disequilibrium (LD), and the need to account for population structure, that is to say, confounding due to genetic ancestry.We propose an efficient approach for the multivariate analysis of multi-population GWAS data based on a multitask group Lasso formulation. Each task corresponds to a subpopulation of the data, and each group to an LD-block. This formulation alleviates the curse of dimensionality, and makes it possible to identify disease LD-blocks shared across populations/tasks, as well as some that are specific to one population/task. In addition, we use stability selection to increase the robustness of our approach. Finally, gap safe screening rules speed up computations enough that our method can run at a genome-wide scale.To our knowledge, this is the first framework for GWAS on diverse populations combining feature selection at the LD-groups level, a multitask approach to address population structure, stability selection, and safe screening rules. We show that our approach outperforms state-of-the-art methods on both a simulated and a real-world cancer datasets.

Clustering of risk factors in the smoking habits of schoolchildren in Sousse, Tunisia.

BACKGROUND: In Tunisia, little is known about the association between tobacco use and other chronic disease risk factors. This is the case for both adults and children. It is important to know the characteristics of young smokers to facilitate the creation and implementation of future programs for tobacco prevention. AIM: The aim of this study was to determine the association between tobacco use and other lifestyle factors among schoolchildren in Tunisia. METHODS: We conducted a 2009/2010 cross-sectional questionnaire survey of 4003 randomly selected school children aged 13 years old (7th and 9th grades) to evaluate their knowledge, attitudes towards, and beliefs about the three risk factors for chronic disease (unhealthy diet, physical inactivity, and tobacco use). Written informed consent was obtained from each child's parents who allowed their child to participate. RESULTS: The mean age of our sample was 13.36 ± 1.28 years. The proportions of daily smokers were 2.2% and 0.1% among boys and girls, respectively. The proportions of irregular smokers were 9.1% and 1.5% among boys and girls, respectively. In our population, 19.1% (n=767) had ever experimented to smoke, with 29.8% among boys and 9% among girls (p<0.001). The proportions of schoolchildren who reported daily participation in physical activity were different between smokers and nonsmokers with 17.7% and 11.5%, respectively (p=0.03). Concerning eating habits, there was no significant difference in the consumption of fruits and vegetables; however, smokers frequently ate more high fat foods and in fast food restaurants. Similar results were found while comparing regular smoking children with those who experimented but who never became hooked on smoking. CONCLUSION: This study and previous research suggest the importance of early intervention in adolescents on smoking and combing these efforts with interventions focusing on physical activity and dietary habits.

Advising Obese Adults about Diet and Physical Activity in Sousse, Tunisia.

Background. To our knowledge no study has been conducted in Tunisia to describe practice of health care providers towards chronic disease risk factors, particularly among obese adults. Aim. This study is aimed at assessing the level of giving advice on diet and physical activity by health care providers for obese adults comparing to nonobese adults in Tunisia. Methods. A cross-sectional survey was carried out in 2010 for adults aged from18 to 65 years living in the region of Sousse. The questionnaires were administered by an interview made by trained data collectors to standardize the administration of the questionnaire. Anthropometric measurements of height and weight were obtained using a standardized protocol from each participant. Results. The findings from this study indicate that obesity is frequent among adults essentially among women and aged categories. It also shows that obese adults are not adequately diagnosed with few proportion of anthropometric measure evaluation among all the participants. Even if obese participants were significantly more advised than nonobese participants with, respectively, 28.5% to lose weight and 23.8% to increase physical activity, this proportion remains low.