Browsing by Subject "Epidemiology"

Thanks to modern medical advances, humans have developed tools for detecting diseases so early, that a patient would be better off had the disease gone undetected. This is called overdiagnosis. Overdiagnosisisaproblemespeciallycommoninacts,wherethetargetpopulationofanintervention consists of mostly healthy people. Colorectal cancer (CRC) is a relatively rare disease. Thus screening for CRC affects mostly cancerfree population. In this thesis I evaluate overdiagnosis in guaiac faecal occult blood test (gFOBT) based CRC screening programme. In gFOBT CRC screening there are two goals: to detect known predecessors of cancers called adenomas and to remove them (cancer prevention), and to detect malign CRCs early enough to be still treatable (early detection). Overdiagnosis can happen when detecting adenomas, but also when detecting cancers. This thesis focuses on overdiagnosis due to detection of adenomas that are non-progressive in their nature. Since there is no clinical means to make distinction between progressive and non-progressive adenomas, statistical methods must be applied. Classical methods to estimate overdiagnosis fail in quantifying this type of overdiagnosis for couple of reasons: incidence data of adenomas is not available, and adenoma removal results in lowering cancer incidence in screened population. While the latter is a desired effect of screening, it makes it impossible to estimate overdiagnosis by just comparing cancer incidences among screened and control populations. In this thesis a Bayesian Hidden Markov model using HMC NUTS algorithm via software Stan is fitted to simulate the natural progression of colorectal cancer. The five states included in the model were healthy (1), progressive adenoma (2), screen-detectable CRC (3), clinically apparent CRC (4) and non-progressive adenoma (5). Possible transitions are from 1 to 2, 1 to 5, 2 to 3 and 3 to 4. The possible observations are screen-negative (1), detected adenoma (2), screen-detected CRC (3), clinically manifested CRC (3). Three relevant estimands for evaluating this type of overdiagnosis with a natural history model are presented. Then the methods are applied to estimate overdiagnosis proportion in guaiac faecal occult blood test (gFOBT) based CRC screening programme conducted in Finland between 2004 and 2016. The resulting mean overdiagnosis probability for all the patients that had an adenoma detected for programme is 0.48 (0.38, 0.56, 95-percent credible interval). Different estimates for overdiagnosis in sex and age-specific stratas of the screened population are also provided. In addition to these findings, the natural history model can be used to gain more insight about natural progression of colorectal cancer.

Respiratory diseases such as asthma and COPD create a significant disease burden worldwide. Data used in this paper was collected in 2016 in FinEsS-Helsinki-study regarding respiratory diseases, their symptoms and risk factors. Later, the respondents were asked to submit a permission to collect personal socioeconomic data from several authorities as a part of Nordic EpiLung-study. The aim of this paper was to analyze if there are differences between non-responders and responders in different background variables, lung diseases or medication using the original FinEsS-data. Response rate in epidemiological surveys has declined during the last decades. Non-responder-studies offer valuable information regarding the impacts of this phenomenon on study results. Significant differences between non-responders and responders were found in lung diseases, medication and following background variables: age, gender, smoking, exercise, comorbidities and predisposing factors. Most non-responders were found among younger age-groups, smokers, electronic cigarette smokers, those with panic disorder or anxiety disorder and those being exposed to dust, gases and smoke in their working environment. Most responders were found among those receiving treatment/medication for dyspepsia or gastroesophageal reflux and the users of asthma medication. The results of this study can be used as a part of Epilung-study to assess the reliability of the effect of socioeconomic factors on respiratory health.

Keuhkojen matalan maligniteettiasteen neuroendokriiniset kasvaimet eli keuhkokarsinoidit ovat harvinaisia pahanlaatuisia kasvaimia, joita tavataan kaikissa ikäryhmissä. Niille altistavia tekijöitä ei tunneta: yleisemmistä keuhkosyöpätyypeistä poiketen esimerkiksi tupakoinnilla ei ole havaittu olevan yhteyttä sairastumisriskiin. Keuhkokarsinoidit jaetaan mikroskopiassa nähtävien ominaisuuksien eli histologisen kuvan perusteella tyypillisiin ja atyyppisiin kasvaimiin. Hoito on molemmissa histologisissa tyypeissä ensisijaisesti leikkaus, kun taas sädehoidon ja solusalpaajien merkitys on vähäinen. Kyseisten kasvainten ennuste on erinomainen erityisesti tyypillisissä kasvaimissa heijastaen niiden matalaa maligniteettiastetta eli hidasta paikallista leviämistä ja taipumusta lähettää etäpesäkkeitä harvoin. Tämän tutkielman tavoitteena on tarkastella keuhkokarsinoidien esiintymistä suomalaisessa väestössä Suomen Syöpärekisterin tietojen pohjalta. Tiedot vuosina 1971-2012 Syöpärekisteriin ilmoitetuista 689 tapauksesta toimitettiin tietosuojatusti, ja jokainen tapaus arvioitiin kriittisesti uudelleen saatavissa olevan rekisteritiedon pohjalta. Vuosittain todettujen uusien keuhkokarsinoidien määrän havaittiin kasvaneen 1970-luvulta eteenpäin, mutta tämä lienee ennemmin diagnostisten menetelmien kehityksestä kuin todellisesta taudin yleistymisestä johtuva havainto. Valtaosa kasvaimista oli luokiteltu histologiselta kuvaltaan tyypillisiksi. Pitkäaikaisennusteen havaittiin olevan erittäin hyvä erityisesti tyypillisissä kasvaimissa. Huonomman ennusteen lisäksi atyyppisillä kasvaimilla havaittiin useammin taudin toteamishetkellä levinneisyyttä alueellisiin imusolmukkeisiin tai sitä laajemmalle kuvastaen niiden aggressiivisempaa taudinkuvaa tyypillisiin kasvaimiin verrattuna. Tautia havaittiin esiintyvän lähes kaikissa ikäryhmissä, ja jopa hieman yli kolmannes kasvaimista todettiin alle 50-vuotiailla potilailla. Nämä suomalaisessa aineistossa saadut tulokset ovat hyvin linjassa aiempien tutkimusten kanssa. Aiempia vastaavia tutkimuksia suomalaisessa väestössä ei ole julkaistu.

Background: Oral contraceptive (OC) use may increase the risk of specific cancers and mortality. The aims of this study were to investigate the association between OC use and its duration with the risk of breast cancer, to examine the overall mortality associated with OC use and its duration, and finally to identify sociodemographic characteristics of OC use. Methods: Data are derived from the Older Finnish Twin cohort consisted of monozygotic and same-sexed dizygotic twin pairs born before 1958. We included N = 9,607 Finnish twin women aged 18 – 49 years old with information on OC use and other covariates. The information on OC use, reproductive, and lifestyle factors was collected using a mailed questionnaire. The information on breast cancer incidence was obtained from the Finnish Cancer Registry and the data on mortality was collected from the national Population Information System and Statistics Finland. We used Cox proportional hazards regression to estimate the association between OC use and its duration with risk of breast cancer and overall mortality while controlling for potential confounders. Also, we used logistic regression to identify sociodemographic characteristics of OC use. All tests of statistical significance were two-sided. Results: A total of 758 women developed breast cancer during median follow-up of 42.6 years. Women who ever used OC had 20% greater risk of developing breast cancer than women who never used (HR =1.20, 95% CI = 1.02 to 1.40, P = 0.02). Women who used OC for more than 5 years had greater risk of developing the disease than those who used OC for less than 2 years (HR = 1.11, 95% CI = 0.85 to 1.46), however, the results did not reach the statistical significance. Mortality did not significantly different between women who had ever used OC with those who had not used OC while controlling for potential confounders. Current smokers and women who consumed alcohol more than 10 gram/day had the highest odds of ever using OC. Conclusion: Our results suggest that OC use slightly increases the risk of breast cancer, however, no evidence from this study indicates that OC use adversely affect long-term risk for mortality.

Schistosomiasis and soil-transmitted helminthiasis (STH) are major public health problems in tropical and subtropical countries. In 2006, the World Health Organization launched a new strategy against helminth infections, based on the concept of preventive chemotherapy. Ac-cording to this recommendation, anthelminthic drugs should be distributed to all at risk of infection, with the aim of reducing morbidity and the intensity of infection. This report describes the process of constructing an epidemiological database, which attempts to incorporate all information available on the global prevalence of STH, schistosomiasis and other helminthiases. This database can be used as a tool for the implementation of preventive chemotherapy. The aim is also to gather information on the availability of epidemiological data on helminth infections. I found out that data on STH and schistosomiasis are lacking especially in Sub-Saharan Africa. Better data collection and communication between WHO and endemic countries should therefore be developed.