| 1. |
- Biström, Martin, 1982-
(författare)
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Environmental risk factors for the occurrence of multiple sclerosis
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background. Multiple sclerosis (MS) is an inflammatory and degenerative disease of the central nervous system that typically debuts around age 30. About 2.3 million people are affected in the world today, and besides trauma it is the most common cause of neurological disability among young adults in the western world. The disease likely develops via a complex interplay of genetic vulnerability and environmental risk factors, and adolescence is assumed to be a critical time for disease initiation. The aim of this study was to investigate how MS risk in different age groups is influenced by vitamin D, infections with Epstein-Barr virus and Human herpesviruses 6A and B as well as the metabolic markers leptin and insulin.Methods. In this nested case-control study we identified pre-symptomatically drawn blood samples from individuals below age 40, that later developed relapsing remitting MS. This was done through crosslinking of the Swedish MS registry, or a local database, with six Swedish biobanks containing remainders of samples used in microbiological analyses. For each case, one control matched for biobank, sex, date of sampling and age of sampling was selected. These samples were then analysed to determine antibody reactivity against Epstein-Barr virus and Human herpesvirus 6A and B, as well as measure concentrations of leptin, insulin and 25-hydroxyvitamin D. The effect of these variables on MS risk was estimated using conditional logistic regression, both in the entire case-control material as well as stratified into three groups by age at sampling (<20, 20-29 and 30-39) and by sex.Results. Human herpesvirus 6A, but not B, was consistently associated with an increased risk of developing MS. In contrast, Epstein-Barr virus demonstrated an age dependent pattern indicating that early infection may be protective against MS while later infection increases the risk. As for the metabolic markers, insulin was not associated with MS while elevated levels of leptin showed an association with increased MS risk both among individuals below 20 years of age and among all men. For women there was instead an inverse association in the oldest group, aged 30-39, when adjusting the leptin analysis for insulin concentrations. Finally, having vitamin D concentrations in the top quintile was associated with decreased MS risk, without evidence of a stronger effect in young subjects.Conclusion. These results implicate Human herpesvirus 6A and leptin as risk factors for MS development. They also further support a protective role for vitamin D in MS etiology and provide serological evidence of an age dependency of Epstein-Barr virus infection as it relates to MS risk.
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| 2. |
- Widbom, Lovisa, 1994-
(författare)
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Lifestyle, biomarkers and the risk of developing inflammatory bowel disease
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn’s disease (CD), is a chronic disease causing inflammation in the gut mucosa. The pathogenesis involves alteration in gut microbiota and in the intestinal barrier due to genetic factors, environmental exposure and dysregulation of the immune response. Several environmental risk factors and risk genes have been identified, but still, the pathogenesis is not fully understood. Methods: Included papers are all case-control studies based on previously collected data stored with the biobank in Umeå, Sweden. Cases are individuals that participated in the Northern Sweden Health and Disease Study (NSHDS) at least one year before developing IBD. Information was available for all cases regarding age, time and place for inclusion in NSHDS, height and weight, sex and tobacco use. Part of the cases also had available data from a detailed food-frequency questionnaire. For each available case, controls matched for age, sex and time and place were selected. Analysed factors included tobacco use, with smoking and snuff use analysed separately), cotinine (a metabolite of nicotine), iron status (including ferritin, iron, transferrin and transferrin saturation), B-vitamins and tryptophan metabolites. Results: Smoking was associated with an increased risk of developing IBD both based on questionnaire data and using cotinine as a marker for exposure. Snuff use was not associated with risk for developing IBD. A lower ferritin was associated with an increased risk of developing IBD, whereas no association was seen for other iron status analytes. When analysing iron deficiency based on ferritin and CRP, it was shown that iron deficiency was more common among men before onset of IBD, whereas no difference was seen for women. Active vitamin B6 was lower among cases compared to controls, as well as an index indicating functional B6 deficiency. Kynurenic acid and xanthurenic acid, both tryptophan metabolites with immunomodulatory properties, were lower among cases than controls. For CD only, picolinic acid was lower among cases later developing IBD.Discussion: Smoking increases the risk of developing both UC and CD. Snuff use did not increase the risk for IBD, indicating that tobacco exposure is not the reason for increased IBD risk. Low ferritin indicates an early pathological process affecting iron storage unrelated to inflammation. Changes in vitamin B6 and tryptophan metabolites might indicate early pathological processes possibly related to gut microbiota changes. To conclude, this dissertation shows that multiple differences between individuals later developing IBD and controls can be seen years before IBD diagnosis. Some of which give insight to early pathophysiology in IBD.
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| 3. |
- Ekblom, Kim, 1970-
(författare)
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Oxidants and antioxidants in cardiovascular disease
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background Cardiovascular diseases, including myocardial infarction and stroke, are the main reason of death in Sweden and Western Europe. High iron stores are believed to produce oxygen radicals, which is the presumed putative mechanism behind lipid peroxidation, atherosclerosis and subsequent cardiovascular disease. Iron levels are associated with the hemochromatosis associated HFE single nucleotide polymorphisms C282Y and H63D. Bilirubin is an antioxidant present in relatively high levels in the human body. Several previous studies have found an association between high bilirubin levels and a lower risk for cardiovascular disease. Bilirubin levels are highly influenced by the common promoter polymorphism TA-insertion UGT1A1*28, the main reason for benign hyperbilirubinemia in Caucasians. There is a lack of prospective studies on both the association of iron and bilirubin levels, and the risk for myocardial infarction and ischemic stroke. Material and methods Iron, transferrin iron saturation, TIBC, ferritin and bilirubin were analyzed and HFE C282Y, HFE H63D and UGT1A1*28 were determined in myocardial infarction and stroke cases, and their double matched referents within the Northern Sweden Health and Disease Study Cohort. Results There were no associations between iron levels in the upper normal range and risk for myocardial infarction or stroke. No associations were seen for HFE-genotypes, except for a near fivefold increase in risk for myocardial infarction in HFE H63D homozygous women. Plasma bilirubin was lower in cases vs. referents both in the myocardial infarction and the stroke cohort. Despite a strong gene-dosage effect on bilirubin levels in both cases and referents, the UGT1A1*28 polymorphism did not influence the risk for myocardial infarction or stroke. Conclusion High iron stores are not associated with increased risk for neither myocardial infarction, nor stroke. There was no association between UGT1A1*28 and the risk for myocardial infarction or stroke. Consequently data suggests that other factors, which also may lower bilirubin, are responsible for the elevated risk observed in conjunction with lower bilirubin levels.
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| 4. |
- Wallin, Olof, 1976-
(författare)
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Preanalytical errors in hospitals : implications for quality improvement of blood sample collection
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Most errors in the venous blood testing process are preanalytical, i.e. they occur before the sample reaches the laboratory. Unlike the laboratory analysis, the preanalytical phase involves several error-prone manual tasks not easily avoided with technological solutions. Despite the importance of the preanalytical phase for a correct test result, little is known about how blood samples are collected in hospitals. Aim: The aim of this thesis was to survey preanalytical procedures in hospitals to identify sources of error. Methods: The first part of this thesis was a questionnaire survey. After a pilot study (Paper I), a questionnaire addressing clinical chemistry testing was completed by venous blood sampling staff (n=314, response rate 94%) in hospital wards and hospital laboratories (Papers II–IV). The second part of this thesis was an experimental study. Haematology, coagulation, platelet function and global coagulation parameters were compared between pneumatic tube-transported samples and samples that had not been transported (Paper V). Results: The results of the questionnaire survey indicate that the desirable procedure for the collection and handling of venous blood samples were not always followed in the wards (Papers II–III). For example, as few as 2.4% of the ward staff reported to always label the test tube immediately before sample collection. Only 22% of the ward staff reported to always use wristbands for patient identification, while 18% reported to always use online laboratory manuals, the only source of updated information. However, a substantial part of the ward staff showed considerable interest in re-education (45%) and willingness to improve routines (44%) for venous blood sampling. Compared to the ward staff, the laboratory staff reported significantly higher proportions of desirable practices regarding test request management, test tube labelling, test information search procedures, and the collection and handling of venous blood samples, but not regarding patient identification. Of the ward staff, only 5.5% had ever filed an error report regarding venous blood sampling, compared to 28% of the laboratory staff (Paper IV). In the experimental study (Paper V), no significant preanalytical effect of pneumatic tube transport was found for most haematology, coagulation and platelet function parameters. However, time-to-clot formation was significantly shorter (16%) in the pneumatic tube-transported samples, indicating an in vitro activation of global coagulation. Conclusions. The questionnaire study of the rated experiences of venous blood sampling ward staff is the first of its kind to survey manual tasks in the preanalytical phase. The results suggest a clinically important risk of preanalytical errors in the surveyed wards. Computerised test request management will eliminate some, but not all, of the identified risks. The better performance reported by the laboratory staff may reflect successful quality improvement initiatives in the laboratories. The current error reporting system needs to be functionally implemented. The experimental study indicates that pneumatic tube transport does not introduce preanalytical errors for regular tests, but manual transport is recommended for analysis with thromboelastographic technique. This thesis underscores the importance of quality improvement in the preanalytical phase of venous blood testing in hospitals.
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| 5. |
- Lundqvist, Anette, 1963-
(författare)
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Nutritional aspects of behaviour and biology during pregnancy and postpartum
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundA well-balanced nutritious diet is important for the pregnant woman and the growing fetus, as well as for their future health. Poor nutrition results from both over-consumption of energy-rich foods which can lead to a higher weight gain than is healthy and under-nutrition of essential nutrients. Food intake is regulated in complex biological systems by many factors, where steroid hormone is one factor involved.The overall aim of this thesis is to describe dietary intake, vitamin D levels, dietary information and dietary changes, and to study the relation between allopregnanolone and weight gain during pregnancy and postpartum.Methods Study I was a qualitative study with focus group interviews with 23 pregnant women. The text was analysed with content analysis. Study II was a quantitative cross-sectional study conducted in early pregnancy (n=209) with a reference group (n=206). Self-reported dietary data from a questionnaire was analysed using descriptive comparative statistics and a cluster analysis model (Partial Least Squares modelling). Study III had a quantitative longitudinal design. Vitamin D concentrations were analysed in 184 women, collected on five occasions during pregnancy and postpartum. Descriptive comparative statistics and a linear mixed model were used. Study IV was a quantitative longitudinal study with 60 women. Concentrations of allopregnanolone were analysed in gestational week 12 and 35. Descriptive and comparative statistics as well as Spearman’s correlation (rho) were used to describe the relationship between weight gain and allopregnanolone concentrations. Results The focus group interviews showed that women wanted to know more about different foods to reduce any risk for their child but the information about foods was partly up to themselves to find out. They expressedfeelingsof insecurityand guiltif they accidentallyate something“forbidden”. The recommendationswere followedas best as possiblealong withcommon sense todeal with dietchanges. The main themes were “Finding out by oneself”, “Getting professional advice when health problems occur”, “Being uncertain” and “Being responsible with a pinch of salt”. Some differences in the dietary patterns were found among the pregnant women compared to references, with less, vegetables (47 g/day), potatoes/rice/pasta (31 g/day), meat/fish (24 g/day) and intake of alcohol and tobacco/snuff but a higher intake of supplements. Bothpregnant women and referenceshad intakes offolatethrough diet45% (pregnant) and 22% (references) lower than current recommendations(500vs400g/day). Vitamin Dintake was34% lower than the recommendationsof 10mg/day. At least a third of the participants had insufficient plasma levels below 50 nmol/L of vitamin D. Season was a strong factor influencing the longitudinal pattern. Gestational week, season, total energy intake, dietary intake of vitamin D, and multivitamin supplementation over the previous 14 days were factors related to vitamin D levels. A correlation betweenallopregnanoloneconcentrations ingestationalweek 35and weight gainin weeks12–35was seen (p = 0.016). Therewas alsoa correlation betweenthe increase inallopregnanolone(weeks12–35) andweight gain(see above) (p = 0.028). ConclusionsDietary recommendations were described as contradictory and confusing and the dietary advice felt inadequate. The women faced their diet changes and sought information on their own but would have wished for more extensive advice from the midwife. The intake of vitamins essential for pregnancy was lower than recommended, which is also confirmed by low plasma levels of vitamin D in at least one third of the pregnant women. Vitamin D levels peaked in late pregnancy. Aside from gestational week and season which were related to plasma levels, intake from foods and supplements also affected the levels. Reasons for weight gain are complex and depend on many factors. Allopregnanolone is a factor that was seen to relate to the weight gain of the studied pregnant women.
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| 6. |
- Söderström, Elisabet, 1975-
(författare)
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Homocysteine and its determinants in relation to cardiovascular risk factors and myocardial infarction
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Globally, cardiovascular diseases (CVD), including myocardial infarction (MI) and stroke, are the leading cause of illness and death and constitute a significant part of the disease burden in Sweden and Western Europe. Age, hypertension, smoking, obesity, dyslipoproteinemia, diabetes, and impaired renal function are considered established risk factors for CVD. However, these factors do not explain all MI cases, and much is still unknown. Homocysteine is a sulfur-containing amino acid used in clinical practice as a biomarker of functional vitamin B12 and folate status. Earlier observational studies have shown associations with higher plasma homocysteine concentrations (tHcy) and CVD. The causal relationship between tHcy and MI has been debated as homocysteine-lowering prevention studies have not shown a protective effect on MI, although there may be a protective effect on ischemic stroke. Still, tHcy is a prognostic biomarker or risk determinant of MI. There is a need for more knowledge on the pathophysiologic mechanisms of how homocysteine interacts with its determinants, and other risk factors, on the risk of MI.Aims: The overall aim of the thesis was to expand knowledge about how homocysteine, as a risk determinant, can have an impact on cardiovascular disease. Specifically, the purposes were to explore the associations between tHcy, determinants of homocysteine and risk factors of CVD, and the associated risk of prospectively developing a first-ever MI.Material and methods: In papers I, III, and IV, a prospective incident nested case-referent study design was used with 545 cases of MI and 1054 matched referents. In paper II the design was cross-sectional, comparing strictly defined smokers and snus users. All study subjects emanated from the Northern Sweden Health and Disease Study (NSHDS). Blood samples stored frozen at -80ºC were later thawed, and analyses of biomarkers for renal function, lipids, B-vitamins, tHcy, cotinine, and genetic polymorphisms related to homocysteine metabolism were performed. Results: In a prospective setting, folate, but not tHcy, was positively associated with apolipoprotein A1 (Apo A1). The association was seen among referents and not among those later developing an MI. Among strictly defined smokers and snus users, cotinine was positively associated with tHcy among smokers but not among snus users, despite higher cotinine concentrations in snus users. No association was observed between tHcy and the number of cigarettes/day.The CTH G1208T and MTHFR A1298C polymorphisms were, among women, associated with a higher risk of developing a first-ever MI with a fatal outcome. No such associations were seen among men or all MI patients. Further, no associations were seen between the MTHFR C677T polymorphism and the risk of having an MI, fatal or non-fatal. Mild impairment of renal glomerular function defined by eGFRcystatin C /eGFRcreatinine ratio and the associated risk of MI is previously not studied prospectively. In the present study, a lower eGFRcystatin C/eGFRcreatinine ratio was associated with a higher risk of later developing a first-ever MI among women, both when analyzed as a continuous variable and across the quartiles of the ratio. These associations did not appear among men.Conclusions: The independent association of folate but not tHcy with Apo A1 emphasizes the need to adjust for possible confounding effects in studies on homocysteine and endpoints or biomarkers. The results suggest a possible link between one-carbon metabolism and lipid metabolism. The independent association between cotinine and tHcy in smokers and not among snus users indicate that nicotine per se may not mediate higher tHcy concentrations. Cotinine concentrations in plasma appeared as a better predictor of tHcy than self-reported smoking data. Thus, whenever possible, self-reported smoking should be supplemented by biomarkers, such as cotinine, in epidemiological studies. After outcome stratification, fatal or non-fatal MI, the associated higher risk among women of a fatal MI and CTH G1208T and MTHFR A1298C polymorphisms, respectively, may indicate that women with the minor alleles risk having a more serious MI leading to death than women with the wild-type alleles. In a prospective setting, the eGFRcystatin C/eGFR creatinine ratio was associated with an increased risk of later developing a first-ever MI among women. The eGFRcystatin C/eGFRcreatinine ratio may be a tool, easily implemented at clinical laboratories, for evaluating the risk of having a future first-ever MI.
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