Helicobacter pylori in Vammala, Finland: seroepidemiological studies and a population-based ‘screen-and-treat’ programme

Helicobacter pylorin (helikobakteeri) tartunta saadaan yleensä lapsena ja tauti jää tavallisesti pysyväksi ilman täsmähoitoa. Onnistunut hoito parantaa pysyvästi helikobakteerista aiheutuvan mahan haavataudin ja näyttää ehkäisevän mahalaukun pahanlaatuisten muutosten kehittymistä. Aloitimme Vammalassa terveyskeskuksessa toteutetun kansainvälisesti ainutlaatuisen väestöpohjaisen helikobakteeritulehduksen seulonta- ja hoito-ohjelman pilottitutkimuksella 1994. 1996 kaikki 15-40-vuotiaat ja 1997-2000 15- ja 45-vuotiaat vammalalaiset kutsuttiin verinäyteseulontaan. Yhteensä 4626 henkilöä (75% kutsutuista) osallistui seulontaan. Vasta-ainepositiivisille tarjottiin helikobakteeritulehduksen lopettava lääkekuuri. Toiminnan seurauksena helikobakteeritulehduksen esiintyvyyden laskettiin vähentyneen 12%:sta 4%:iin 15-40-vuotiaiden ikäryhmässä. Tutkimme myös helikobakteerivasta-ainepositiivisten ja -negatiivisten eroja sekä helikobakteeritulehduksen riskitekijöitä kyselytutkimuksella. Lapsuudenkodin asumisahtauden, äidin matalan koulutusasteen, tupakoinnin, alkoholinkäytön, huonojen asunto-olojen ja ylävatsavaivoista johtuvien sairauslomien todettiin liittyvän helikobakteeritulehdukseen monimuuttuja-analyysissa. Tutkimme seulontaohjelmassa käyttämiemme IgG- ja IgA-luokan helikobakteeri-vasta-ainetestien luotettavuutta eri ikäryhmissä ottaen huomioon atrofisen gastriitin esiintyvyyden. 561 kliinisin perustein gastroskopoidun potilaan aineistossa IgG-testi osoittautui erittäin herkäksi kaikissa ikäryhmissä (99%). Tarkkuus oli myös vanhemmissa ikäryhmissä hyvä (97-93%), kun atrofista gastriittia sairastavat suljettiin pois. IgA- ja CagA-helikobakteerivasta-aineiden on todettu liittyvän lisääntyneeseen mahahaava- ja mahasyöpäriskiin. Analysoimme 560 henkilön pariseeruminäytteet, jotka oli otettu kahden vuosikymmenen välein, ja totesimme, että IgA-vasta-aineiden esiintyvyyden lisääntyyminen iän myötä johtuu paitsi syntymäajankohdasta ja uusista infektioista myös IgA-vasta-ainetasojen kohoamisesta helikobakteeritulehduksen aikana. Selvitimme myös CagA-vasta-ainetasojen muuttumista analysoimalla seeruminäytteet, jotka oli otettu kahden vuosikymmenen välein. Totesimme, että samanaikaisesti kun helikobakteerin esiintyvyys väestössä on alentunut, erityisesti CagA-positiiviset infektiot ovat vähentyneet. Tutkimuksemme osoittaa, että Suomessa terveyskeskuksen yhteydessä voidaan toteuttaa näin laajamittainen seulonta- ja hoito-ohjelma, johon suomalaiset osallistuvat aktiivisesti. Nähtäväksi jää, kuinka paljon ohjelma kykeni vähentämään helikobakteeritulehdukseen liittyviä myöhäisseuraamuksia.

Quantum Chemical Studies on Tropospheric Nucleation Mechanisms Involving Sulfuric Acid

Nucleation is the first step of the process by which gas molecules in the atmosphere condense to form liquid or solid particles. Despite the importance of atmospheric new-particle formation for both climate and health-related issues, little information exists on its precise molecular-level mechanisms. In this thesis, potential nucleation mechanisms involving sulfuric acid together with either water and ammonia or reactive biogenic molecules are studied using quantum chemical methods. Quantum chemistry calculations are based on the numerical solution of Schrödinger's equation for a system of atoms and electrons subject to various sets of approximations, the precise details of which give rise to a large number of model chemistries. A comparison of several different model chemistries indicates that the computational method must be chosen with care if accurate results for sulfuric acid - water - ammonia clusters are desired. Specifically, binding energies are incorrectly predicted by some popular density functionals, and vibrational anharmonicity must be accounted for if quantitatively reliable formation free energies are desired. The calculations reported in this thesis show that a combination of different high-level energy corrections and advanced thermochemical analysis can quantitatively replicate experimental results concerning the hydration of sulfuric acid. The role of ammonia in sulfuric acid - water nucleation was revealed by a series of calculations on molecular clusters of increasing size with respect to all three co-ordinates; sulfuric acid, water and ammonia. As indicated by experimental measurements, ammonia significantly assists the growth of clusters in the sulfuric acid - co-ordinate. The calculations presented in this thesis predict that in atmospheric conditions, this effect becomes important as the number of acid molecules increases from two to three. On the other hand, small molecular clusters are unlikely to contain more than one ammonia molecule per sulfuric acid. This implies that the average NH3:H2SO4 mole ratio of small molecular clusters in atmospheric conditions is likely to be between 1:3 and 1:1. Calculations on charged clusters confirm the experimental result that the HSO4- ion is much more strongly hydrated than neutral sulfuric acid. Preliminary calculations on HSO4- NH3 clusters indicate that ammonia is likely to play at most a minor role in ion-induced nucleation in the sulfuric acid - water system. Calculations of thermodynamic and kinetic parameters for the reaction of stabilized Criegee Intermediates with sulfuric acid demonstrate that quantum chemistry is a powerful tool for investigating chemically complicated nucleation mechanisms. The calculations indicate that if the biogenic Criegee Intermediates have sufficiently long lifetimes in atmospheric conditions, the studied reaction may be an important source of nucleation precursors.

Anthropometric measures of obesity-their association with type 2 diabetes and hypertension across ethnic groups

Clinical trials have shown that weight reduction with lifestyles can delay or prevent diabetes and reduce blood pressure. An appropriate definition of obesity using anthropometric measures is useful in predicting diabetes and hypertension at the population level. However, there is debate on which of the measures of obesity is best or most strongly associated with diabetes and hypertension and on what are the optimal cut-off values for body mass index (BMI) and waist circumference (WC) in this regard. The aims of the study were 1) to compare the strength of the association for undiagnosed or newly diagnosed diabetes (or hypertension) with anthropometric measures of obesity in people of Asian origin, 2) to detect ethnic differences in the association of undiagnosed diabetes with obesity, 3) to identify ethnic- and sex-specific change point values of BMI and WC for changes in the prevalence of diabetes and 4) to evaluate the ethnic-specific WC cutoff values proposed by the International Diabetes Federation (IDF) in 2005 for central obesity. The study population comprised 28 435 men and 35 198 women, ≥ 25 years of age, from 39 cohorts participating in the DECODA and DECODE studies, including 5 Asian Indian (n = 13 537), 3 Mauritian Indian (n = 4505) and Mauritian Creole (n = 1075), 8 Chinese (n =10 801), 1 Filipino (n = 3841), 7 Japanese (n = 7934), 1 Mongolian (n = 1991), and 14 European (n = 20 979) studies. The prevalence of diabetes, hypertension and central obesity was estimated, using descriptive statistics, and the differences were determined with the χ2 test. The odds ratios (ORs) or  coefficients (from the logistic model) and hazard ratios (HRs, from the Cox model to interval censored data) for BMI, WC, waist-to-hip ratio (WHR), and waist-to-stature ratio (WSR) were estimated for diabetes and hypertension. The differences between BMI and WC, WHR or WSR were compared, applying paired homogeneity tests (Wald statistics with 1 df). Hierarchical three-level Bayesian change point analysis, adjusting for age, was applied to identify the most likely cut-off/change point values for BMI and WC in association with previously undiagnosed diabetes. The ORs for diabetes in men (women) with BMI, WC, WHR and WSR were 1.52 (1.59), 1.54 (1.70), 1.53 (1.50) and 1.62 (1.70), respectively and the corresponding ORs for hypertension were 1.68 (1.55), 1.66 (1.51), 1.45 (1.28) and 1.63 (1.50). For diabetes the OR for BMI did not differ from that for WC or WHR, but was lower than that for WSR (p = 0.001) in men while in women the ORs were higher for WC and WSR than for BMI (both p < 0.05). Hypertension was more strongly associated with BMI than with WHR in men (p < 0.001) and most strongly with BMI than with WHR (p < 0.001), WSR (p < 0.01) and WC (p < 0.05) in women. The HRs for incidence of diabetes and hypertension did not differ between BMI and the other three central obesity measures in Mauritian Indians and Mauritian Creoles during follow-ups of 5, 6 and 11 years. The prevalence of diabetes was highest in Asian Indians, lowest in Europeans and intermediate in others, given the same BMI or WC category. The  coefficients for diabetes in BMI (kg/m2) were (men/women): 0.34/0.28, 0.41/0.43, 0.42/0.61, 0.36/0.59 and 0.33/0.49 for Asian Indian, Chinese, Japanese, Mauritian Indian and European (overall homogeneity test: p > 0.05 in men and p < 0.001 in women). Similar results were obtained in WC (cm). Asian Indian women had lower  coefficients than women of other ethnicities. The change points for BMI were 29.5, 25.6, 24.0, 24.0 and 21.5 in men and 29.4, 25.2, 24.9, 25.3 and 22.5 (kg/m2) in women of European, Chinese, Mauritian Indian, Japanese, and Asian Indian descent. The change points for WC were 100, 85, 79 and 82 cm in men and 91, 82, 82 and 76 cm in women of European, Chinese, Mauritian Indian, and Asian Indian. The prevalence of central obesity using the 2005 IDF definition was higher in Japanese men but lower in Japanese women than in their Asian counterparts. The prevalence of central obesity was 52 times higher in Japanese men but 0.8 times lower in Japanese women compared to the National Cholesterol Education Programme definition. The findings suggest that both BMI and WC predicted diabetes and hypertension equally well in all ethnic groups. At the same BMI or WC level, the prevalence of diabetes was highest in Asian Indians, lowest in Europeans and intermediate in others. Ethnic- and sex-specific change points of BMI and WC should be considered in setting diagnostic criteria for obesity to detect undiagnosed or newly diagnosed diabetes.