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- Myléus, Anna, 1978-
(författare)
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Towards explaining the Swedish epidemic of celiac disease : an epidemiological approach
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Celiac disease occurs worldwide in approximately 1% of the population, whereof the majority of cases are undiagnosed. Sweden experienced an epidemic (1984-1996) of clinically detected celiac disease in children below 2 years of age, partly attributed to changes in infant feeding. Whether the epidemic constituted a change in disease occurrence and/or a shift in the proportion of diagnosed cases remains unknown. Moreover, the cause of the epidemic is not fully understood.Objective: To increase the knowledge regarding the occurrence of celiac disease in Sweden, with focus on the epidemic period and thereafter, as well as the etiology of celiac disease in general, by investigating the Swedish epidemic and its potential causes.Methods: We performed a two-phased cross-sectional multicenter screening study investigating the total prevalence, including both clinically- and screening-detected cases, of celiac disease in 2 birth cohorts of 12-year-olds (n=13 279): 1 of the epidemic period (1993) and 1 of the post-epidemic period (1997). The screening strategy entailed serological markers analyses, with subsequent small intestinal biopsy when values were positive. Diagnosis was ascertained in clinical cases detected prior to screening. Infant feeding practices in the cohorts were ascertained via questionnaires. An ecological approach combined with an incident case-referent study (475 cases, 950 referents) performed during the epidemic were used for investigating environmental- and lifestyle factors other than infant feeding. Exposure information was obtained via register data, a questionnaire, and child health clinic records. All studies utilized the National Swedish Childhood Celiac Disease Register.Results: The total prevalences of celiac disease were 2.9% and 2.2% for the 1993 and 1997 cohorts, respectively, with 2/3 cases unrecognized prior to screening. Children born in 1997 had a significantly lower celiac disease prevalence compared to those born in 1993 (prevalence ratio, 0.75; 95% confidence interval [CI], 0.60-0.93). The cohorts differed in infant feeding; more specifically in the proportion of infants introduced to dietary gluten in small amounts during ongoing breastfeeding. Of the environmental and lifestyle factors investigated, no additional changes over time coincided with the epidemic. Early vaccinations within the Swedish program were not risk factors for celiac disease. Early infections (≥3 parental-reported episodes) were associated with increased risk for celiac disease (adjusted odds ratio [OR] 1.5; 95% CI, 1.1-2.0), a risk that increased synergistically if, in addition to having ≥3 infectious episodes, the child was introduced to gluten in large amounts, compared to small or medium amounts, after breastfeeding was discontinued (OR 5.6; 95% CI, 3.1-10). Early infections probably made a minor contribution to the Swedish epidemic through the synergistic effect with gluten, which changed concurrently. In total, approximately 48% of the epidemic could be explained by infant feeding and early infections.Conclusion: Celiac disease is both unexpectedly prevalent and mainly undiagnosed in Swedish children. Although the cause of the epidemic is still not fully understood, the significant difference in prevalence between the 2 cohorts indicates that the epidemic constituted a change in disease occurrence, and importantly, corroborates that celiac disease can be avoided in some children, at least up to 12 years of age. Our findings suggest that infant feeding and early infections, but not early vaccinations, have a causal role in the celiac disease etiology and that the infant feeding practice – gradually introducing gluten-containing foods from 4 months of age, preferably during ongoing breastfeeding – is favorable.
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| 2. |
- Ng, Nawi, 1974-
(författare)
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Chronic disease risk factors in a transitional country : the case of rural Indonesia
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The epidemic of chronic diseases is largely neglected. Although a threatening burden of chronic diseases is emerging, developing public health efforts for their prevention and control is not yet a priority for trans-national and national health policy makers. Understanding the population burden of risk factors which predict chronic diseases is an important step in reducing the impact of the diseases themselves. Objective: This thesis responds to the increasing burden of chronic diseases worldwide, and aims to illustrate the gap in chronic disease risk factor research in developing countries. The thesis describes and analyses the distribution of chronic disease risk factors in a rural setting in Indonesia. It also describes how smoking, one of the most common risk factors, is viewed by rural Javanese boys. Ultimately, therefore, this thesis aims to contribute to policy and programme recommendations for community interventions in a rural setting in Indonesia Methods: The studies were conducted in Purworejo District, where a Demographic Surveillance System (DSS) has been running since 1994. The Purworejo DSS is part of the INDEPTH network (International Network of field sites for continuous Demographic Evaluation of Populations and Their Health in developing countries). Two representative cross-sectional studies (in 2001 and 2005) were conducted to assess the chronic disease risk factors (including smoking, elevated blood pressure, and overweight and obesity). The first cross-sectional study was followed up in 2002 and 2004. In each study, a total of 3 250 participants (approximately 250 individuals in each sex and age group among 15–74 year olds stratified into 10-year intervals) were randomly selected from the surveillance database from each enumeration area in the surveillance area. Instruments were adopted from the WHO STEPS survey and adapted to local setting. Since many Indonesians start to smoke at an earlier age, a qualitative study using a focus group discussion approach was conducted among school boys aged 13-17 years old to describe and explore beliefs, norms, and values about smoking in a rural setting in Java. Result: Both the rural and urban populations in Purworejo face an unequal distribution of risk factors for chronic diseases. The burden among the most well-off group in the rural area has already reached a level similar to that found in the urban area. Most of the risk factors increased in all age, sex and socioeconomic groups during the period of 2001 to 2005. However, women and the poorest group experienced the greatest increase in risk factor prevalence. The qualitative study showed that cultural resistance against women smoking in Indonesia remains strong. Smoking is being viewed as a culturally internalised habit that signifies transition into maturity and adulthood for boys. Smoking is utilised as a means for socialisation and signifies better socioeconomic status. The use of tobacco in the construction of masculinity underlines the importance of gender specific interventions. National tobacco control policy should emphasise a smoking free society as the norm, especially among boys and men, and regulations regarding the banning of smoking should be enforced at all levels and areas of the community. Within the demographic surveillance setting, it is possible to assess the population and health dynamics. Utilisation of a standardised methodology across sites in INDEPTH will produce comparable population-based data in developing countries. Such comparisons are important in global health. A comparison of smoking transition patterns between a Vietnamese DSS and an Indonesian DSS shows that Indonesian men started smoking regularly earlier and ceased less than Vietnamese men. Compared with Vietnam, which has already signed and ratified the Framework Convention on Tobacco Control, tobacco control activities in Indonesia are still deficient. Conclusion: The thesis concludes that the rural population is not spared from the emerging burden of chronic disease risk factors. The patterning of risks across different socioeconomic groups provides a macro picture of the vicious cycle between poverty and chronic diseases. Understanding of risk factors in a local context through a qualitative study provides insight into cultural aspects relating to risk factor adoption, and will allow the fostering and tailoring of culturally appropriate interventions. Combining data from demographic surveillance sites with the WHO STEP approach to chronic disease risk factor Surveillance addresses basic epidemiological questions on chronic diseases. The use of such data is a powerful advocacy tool in public health decision-making for chronic disease prevention in developing countries. With substantial existing evidence on the effectiveness of chronic disease prevention and intervention programmes, it is vital that Indonesia to starts planning intervention programmes to control the impending chronic disease epidemic, and most importantly, to translate all this evidence into public health action. Keywords: chronic disease, risk factor, demographic surveillance system, smoking, elevated blood pressure, overweight and obesity, population-based intervention
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| 3. |
- Stenlund, Hans
(författare)
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Improving interpretation by orthogonal variation : Multivariate analysis of spectroscopic data
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The desire to use the tools and concepts of chemometrics when studying problems in the life sciences, especially biology and medicine, has prompted chemometricians to shift their focus away from their field‘s traditional emphasis on model predictivity and towards the more contemporary objective of optimizing information exchange via model interpretation. The complex data structures that are captured by modern advanced analytical instruments open up new possibilities for extracting information from complex data sets. This in turn imposes higher demands on the quality of data and the modeling techniques used. The introduction of the concept of orthogonal variation in the late 1990‘s led to a shift of focus within chemometrics; the information gained from analysis of orthogonal structures complements that obtained from the predictive structures that were the discipline‘s previous focus. OPLS, which was introduced in the beginning of 2000‘s, refined this view by formalizing the model structure and the separation of orthogonal variations. Orthogonal variation stems from experimental/analytical issues such as time trends, process drift, storage, sample handling, and instrumental differences, or from inherent properties of the sample such as age, gender, genetics, and environmental influence. The usefulness and versatility of OPLS has been demonstrated in over 500 citations, mainly in the fields of metabolomics and transcriptomics but also in NIR, UV and FTIR spectroscopy. In all cases, the predictive precision of OPLS is identical to that of PLS, but OPLS is superior when it comes to the interpretation of both predictive and orthogonal variation. Thus, OPLS models the same data structures but provides increased scope for interpretation, making it more suitable for contemporary applications in the life sciences. This thesis discusses four different research projects, including analyses of NIR, FTIR and NMR spectroscopic data. The discussion includes comparisons of OPLS and PLS models of complex datasets in which experimental variation conceals and confounds relevant information. The PLS and OPLS methods are discussed in detail. In addition, the thesis describes new OPLS-based methods developed to accommodate hyperspectral images for supervised modeling. Proper handling of orthogonal structures revealed the weaknesses in the analytical chains examined. In all of the studies described, the orthogonal structures were used to validate the quality of the generated models as well as gaining new knowledge. These aspects are crucial in order to enhance the information exchange from both past and future studies.
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