Usefulness of Mendelian randomization in observational epidemiology.

Mendelian randomization refers to the random allocation of alleles at the time of gamete formation. In observational epidemiology, this refers to the use of genetic variants to estimate a causal effect between a modifiable risk factor and an outcome of interest. In this review, we recall the principles of a "Mendelian randomization" approach in observational epidemiology, which is based on the technique of instrumental variables; we provide simulations and an example based on real data to demonstrate its implications; we present the results of a systematic search on original articles having used this approach; and we discuss some limitations of this approach in view of what has been found so far.

Escalating epidemiology of eosinophilic esophagitis: 21 years of prospective population-based documentation in Olten county

Background and Aims: Eosinophilic Esophagitis (EoE) is detected with a dramatically increasingfrequency during the last decades. However, it is still unknown whether this reflects atrue increase in incidence or just an increased awareness by gastroenterologists. We therefore,prospectively assessed incidence and prevalence of EoE in an epidemiologically well definedindicator area over the last 21 years. Methods: Olten County is an area of approximately90,000 inhabitants without pronounced demographic changes during the last two decades.Two EoE-experienced gastroenterologists and one pathology centre are responsible forcovering the gastroenterological service of the area. No public programs for increasingawareness of EoE were implemented in this region. Since 1989 all individuals with confirmeddiagnosis of EoE living in Olten County were entered prospectively into the database. Results:Forty-six patients (76% males, mean age 41±16 yrs) were diagnosed with EoE between1989 and 2009. Ninety-four percent of patients presented with dysphagia. An average annualincidence rate of 1.88/100,000 was found (range 0-8) with a marked increase in the periodfrom 2004 to 2009. The cumulative EoE prevalence rose up to 35.1/100,000 inhabitantsin 2009. No significant change was observed for the median diagnostic delay, as it was 3years from 1989 to 1998 and 2 years from 1999 to 2009 with age < 40 years representinga risk factor for retarded diagnosis. The number of upper endoscopies per year increasedby 63% in the period from 1999 to 2009 compared to the years 1989 to 1998 which ismarkedly less then the increase in the incidence rate of 150% for the same periods. Conclusions:Over the last 21 years, a significant increase in EoE incidence and prevalence wasfound in an epidemiologically stable indicator region of Switzerland. The constant diagnosticdelay, the number of newly diagnosed EoE cases that was much more pronounced thanthe modest increase of performed upper endoscopies, as well as the lack of EoE awarenessprograms in Olten County indicates a true increase in EoE incidence.

Epidemiologie der letalen Missbildungen in der Schweiz. [Epidemiology of fatal abnormalities in Switzerland].

Official certificates of stillbirth and infant death are analysed in the birth cohort of 1979-81. Congenital malformations account for approx. 40% of infant mortality. Cantonal differences in malformation rates are not explained by different incidence of such malformations only, but also by differences in lethality. Incidence of Anencephaly is examined in detail.

La mort subite: de l' épidémiologie à la prévention [Sudden cardiac death: epidemiology and modern therapy].

Sudden Cardiac Death (SCD) has become an important public health challenge in the Western World. In Switzerland near 10,000 people suffer each year from SCD. The survival from SCD to hospital discharge is discouraging (near 5%). Large majority of events occur unexpectedly in the out-of-hospital environment and are not predicted with great accuracy by risk profiling. Because the majority of SCD occur by the mechanism of ventricular fibrillation, community-based defibrillation strategies have emerged as one approach to SCD problem. Newer strategies of defibrillation designed to respond faster to out-of-hospital cardiac arrest, including public access defibrillation, as well as aggressive primary and secondary prevention of coronary artery disease appears as the best approach for successful management of SCD.

The effect of a smoking ban introduction to environmental tobacco smoke exposure in Swiss hospitality workers : Abstracts of the 23rd Annual Conference of the International Society of Environmental Epidemiology (ISEE), September 13-16, 2011, Barcelona, Spain

Background and Aims: To protect the population from environmental tobacco smoke (ETS) Switzerland introduced a nationwide rather heterogeneous smoking ban in May 2010. The exposure situation of non-smoking hospitality workers before and after implementation of the new law is being assessed in a prospective cohort study. Methods: Exposure to ETS was measured using a novel method developed by the Institute for Work and Health in Lausanne. It is a passive sampler called MoNIC (Monitor of NICotine). The nicotine of the ETS is fixed onto a filter and transformed into salt of not volatile nicotine. Subsequently the number of passively smoked cigarettes is calculated. Badges were placed at the workplace as well as distributed to the participants for personal measuring. Additionally a salivary sample was taken to determine nicotine concentration. Results: At baseline Spearman's correlation between workplace and personal badge was 0.47. The average cigarette equivalents per day at the workplace obtained by badge significantly dropped from 5.1 (95%- CI: 2.4 to 7.9) at baseline to 0.3 (0.2 to 0.4) at first follow-up (n=29) three months later (p<0.001). For personal badges the number of passively smoked cigarettes declined from 1.5 (2.7 to 0.4) per day to 0.5 (0.3 to 0.8) (n=16).Salivary nicotine concentration in a subset of 13 participants who had worked on the day prior to the examination was 2.63 ng/ml before and 1.53 ng/ml after the ban (p=0.04). Spearman's correlation of salivary nicotine was 0.56 with workplace badge and 0.79 with personal badge concentrations. Conclusions: Workplace measurements clearly reflect the smoking regulation in a venue. The MoNIC badge proves to be a sensitive measuring device to determine personal ETS exposure and it is a demonstrative measure for communication with lay audiences and study participants as the number of passively smoked cigarettes is an easily conceivable result.

Molecular epidemiology reveals long-term changes in HIV type 1 subtype B transmission in Switzerland.

BACKGROUND: Sequence data from resistance testing offer unique opportunities to characterize the structure of human immunodeficiency virus (HIV) infection epidemics. METHODS: We analyzed a representative set of HIV type 1 (HIV-1) subtype B pol sequences from 5700 patients enrolled in the Swiss HIV Cohort Study. We pooled these sequences with the same number of sequences from foreign epidemics, inferred a phylogeny, and identified Swiss transmission clusters as clades having a minimal size of 10 and containing >or=80% Swiss sequences. RESULTS: More than one-half of Swiss patients were included within 60 transmission clusters. Most transmission clusters were significantly dominated by specific transmission routes, which were used to identify the following patient groups: men having sex with men (MSM) (38 transmission clusters; average cluster size, 29 patients) or patients acquiring HIV through heterosexual contact (HETs) and injection drug users (IDUs) (12 transmission clusters; average cluster size, 144 patients). Interestingly, there were no transmission clusters dominated by sequences from HETs only. Although 44% of all HETs who were infected between 1983 and 1986 clustered with injection drug users, this percentage decreased to 18% for 2003-2006 (P<.001), indicating a diminishing role of injection drug users in transmission among HETs over time. CONCLUSIONS: Our analysis suggests (1) the absence of a self-sustaining epidemic of HIV-1 subtype B in HETs in Switzerland and (2) a temporally decreasing clustering of HIV infections in HETs and IDUs.

Epidemiologie der Osteoporose. [The epidemiology of osteoporosis].

Osteoporosis is characterized by low bone mass, micro architectural impairment of bone tissue, and a subsequent in crease in fracture risk. Fractures or the vertebrae and distal forearm, as well as the proximal femur, or hip fracture, are included. Hip fracture is associated with high mortality, morbidity and medical expenses. There is a dramatic increase in the incidence of hip fracture with age. Hip fracture incidence is 350 times higher in women aged 85 years and over comparatively to women between 35 and 44 years of age. In recent studies in Switzerland, it was observed that the annual age adjusted incidence rate of hip fracture was comparable with similar rates for white population in industrialized countries, although in men the rates were relatively high. Among the major risk factors for osteoporosis are age, female gender, white and Asian race, and menopause. Postmenopausal estrogen replacement therapy reduces bone resorption. Family history of osteoporosis, frail constitution, as well as excessive alcohol intake, cigarette smoking, chronic insufficient nutritional calcium intake and physical inactivity are other risk factors. A cardinal element is the peak bone mass reached in the third or fourth decade of life. Independently of osteoporosis, falls are a key agent in fractures; several medical conditions and drugs increase the risk of falling. There is an enormous social and financial cost of osteoporosis; the annual cost of medical treatment only for hip fracture is close to Fr. 200 million in Switzerland. The burden of osteoporosis is likely to increase in the future because of the demographic aging of the population unless large scale preventive interventions are undertaken.

Risk for Pneumocystis carinii transmission among patients with pneumonia: a molecular epidemiology study.

We report a molecular typing and epidemiologic analysis of Pneumocystis carinii pneumonia (PCP) cases diagnosed in our geographic area from 1990 to 2000. Our analysis suggests that transmission from patients with active PCP to susceptible persons caused only a few, if any, PCP cases in our setting.

Family history of cancer: pooled analysis in the International Head and Neck Cancer Epidemiology Consortium.

Alcohol and tobacco consumption are well-recognized risk factors for head and neck cancer (HNC). Evidence suggests that genetic predisposition may also play a role. Only a few epidemiologic studies, however, have considered the relation between HNC risk and family history of HNC and other cancers. We pooled individual-level data across 12 case-control studies including 8,967 HNC cases and 13,627 controls. We obtained pooled odds ratios (OR) using fixed and random effect models and adjusting for potential confounding factors. All statistical tests were two-sided. A family history of HNC in first-degree relatives increased the risk of HNC (OR=1.7, 95% confidence interval, CI, 1.2-2.3). The risk was higher when the affected relative was a sibling (OR=2.2, 95% CI 1.6-3.1) rather than a parent (OR=1.5, 95% CI 1.1-1.8) and for more distal HNC anatomic sites (hypopharynx and larynx). The risk was also higher, or limited to, in subjects exposed to tobacco. The OR rose to 7.2 (95% CI 5.5-9.5) among subjects with family history, who were alcohol and tobacco users. A weak but significant association (OR=1.1, 95% CI 1.0-1.2) emerged for family history of other tobacco-related neoplasms, particularly with laryngeal cancer (OR=1.3, 95% CI 1.1-1.5). No association was observed for family history of nontobacco-related neoplasms and the risk of HNC (OR=1.0, 95% CI 0.9-1.1). Familial factors play a role in the etiology of HNC. In both subjects with and without family history of HNC, avoidance of tobacco and alcohol exposure may be the best way to avoid HNC.

Prenatal diagnosis and epidemiology of multicystic kidney dysplasia in Europe.

OBJECTIVES: The aim of this study is to describe the prenatal diagnosis and epidemiology of multicystic kidney dysplasia (MCKD). METHODS: The study is based on routinely collected data from a European database of major congenital anomalies including 13 registries with cases born in 1997-2006 and covering 1 458 552 births. RESULTS: There were 601 MCKD cases giving an overall prevalence of 4.12 per 10 000 births with regional variation. In live births, 87% of cases had an isolated renal anomaly and 13% had associated major nonrenal anomalies (chromosomal, syndrome or other major anomalies). For the cases with isolated renal anomalies, 51/386 (11%) and 7/386 (2%) choose to terminate the pregnancy or resulted in an intrauterine fetal death, respectively. The prenatal detection rate was 88% in both unilateral and bilateral cases. Birth outcome differed with 92% of unilateral MCKD cases being liveborn compared with 33% of bilateral MCKD cases. For unilateral MCKD cases, 84% had an isolated renal anomaly compared with 51% of bilateral MCKD cases (p < 0.001). CONCLUSIONS: Cases with unilateral MCKD are mainly liveborn, and only 16% have associated major malformations or a syndrome. Cases with bilateral MCKD are often associated with nonrenal major congenital anomalies or part of a syndrome, and only one third of bilateral MCKD cases in this study were liveborn. Prenatal detection rate of MCKD was high for both unilateral and bilateral cases. © 2014 John Wiley & Sons, Ltd.

Intrauterine devices and endometrial cancer risk : a pooled analysis of the Epidemiology of Endometrial Cancer Consortium

Intrauterine devices (IUDs), long-acting and reversible contraceptives, induce a number of immunological and biochemical changes in the uterine environment that could affect endometrial cancer (EC) risk. We addressed this relationship through a pooled analysis of data collected in the Epidemiology of Endometrial Cancer Consortium. We combined individual-level data from 4 cohort and 14 case-control studies, in total 8,801 EC cases and 15,357 controls. Using multivariable logistic regression, we estimated pooled odds ratios (pooled-ORs) and 95% confidence intervals (CIs) for EC risk associated with ever use, type of device, ages at first and last use, duration of use and time since last use, stratified by study and adjusted for confounders. Ever use of IUDs was inversely related to EC risk (pooled-OR = 0.81, 95% CI = 0.74-0.90). Compared with never use, reduced risk of EC was observed for inert IUDs (pooled-OR = 0.69, 95% CI = 0.58-0.82), older age at first use (≥35 years pooled-OR = 0.53, 95% CI = 0.43-0.67), older age at last use (≥45 years pooled-OR = 0.60, 95% CI = 0.50-0.72), longer duration of use (≥10 years pooled-OR = 0.61, 95% CI = 0.52-0.71) and recent use (within 1 year of study entry pooled-OR = 0.39, 95% CI = 0.30-0.49). Future studies are needed to assess the respective roles of detection biases and biologic effects related to foreign body responses in the endometrium, heavier bleeding (and increased clearance of carcinogenic cells) and localized hormonal changes.

Epidemiology of uveitis in children over a 10-year period.

OBJECTIVES: The aim of the present study is to investigate the demographics, aetiologies, complications, treatments and visual outcomes in paediatric uveitis patients in the French-speaking part of Switzerland. METHODS: Chart review of all patients diagnosed with uveitis before the age of 16 years, presenting to two tertiary referral centres (uveitis and paediatric rheumatology clinics) in Lausanne, Switzerland, between 2000 and 2009. RESULTS: Seventy-nine children (37 girls) were identified, 62 living in Switzerland, 15 in Europe and 2 in North Africa. Median age at first symptoms was 9.0 years (range 1.5-15.8 years), with a median follow-up time of 1.8 years (0-8 years). Both eyes were involved in 51 patients (64.6%). The course was acute in 30.4%, chronic in 60.8% and recurrent in 8.9%. Anterior uveitis occurred in 39.2%, intermediate in 32.9%, posterior in 22.8% and panuveitis in 5.1%. The three main diagnoses were idiopathic uveitis (34.2%), JIA-related uveitis (22.8%) and toxoplasmic retinochoroiditis (15.2%). During the last follow-up visit, the visual acuity (VA) was ≥8/10 in 72% of all eyes with a measurable VA. Cataract (8%), ocular hypertension/glaucoma (8%) and macular fibrosis (4%) were the three most common severe complications. Systemic steroids were given to 56% and biological agents to 24% of patients with inflammatory uveitis. CONCLUSIONS: Uveitis in children can be a devastating disease. A strict classification of aetiologies and a tight collaboration between paediatric rheumatologists and ophthalmologists are important to ensure early control of ocular inflammation and improve long-term visual prognosis.

Relation between atherogenic dyslipidemia and the Adult Treatment Program-III definition of metabolic syndrome (Genetic Epidemiology of Metabolic Syndrome Project).

Genetic Epidemiology of Metabolic Syndrome is a multinational, family-based study to explore the genetic basis of the metabolic syndrome. Atherogenic dyslipidemia (defined as low plasma high-density lipoprotein cholesterol with elevated triglycerides (&lt;25th and &gt;75th percentile for age, gender, and country, respectively) identified affected subjects for the metabolic syndrome. This report examines the frequency at which atherogenic dyslipidemia predicts the metabolic syndrome of the National Cholesterol Education Program Adult Treatment Panel III (ATP-III). One thousand four hundred thirty-six (854 men/582 women) affected patients by our criteria were compared with 1,672 (737 men/935 women) unaffected persons. Affected patients had more hypertension, obesity, and hyperglycemia, and they met a higher number of ATP-III criteria (3.2 +/- 1.1 SD vs 1.3 +/- 1.1 SD, p &lt;0.001). Overall, 76% of affected persons also qualified for the ATP-III definition (Cohen's kappa 0.61, 95% confidence interval 0.59 to 0.64), similar to a separate group of 464 sporadic, unrelated cases (75%). Concordance increased from 41% to 82% and 88% for ages &lt; or =35, 36 to 55, and &gt; or =55 years, respectively. Affected status was also independently associated with waist circumference (p &lt;0.001) and fasting glucose (p &lt;0.001) but not systolic blood pressure (p = 0.43). Thus, the lipid-based criteria used to define affection status in this study substantially parallels the ATP-III definition of metabolic syndrome in subjects aged &gt;35 years. In subjects aged &lt;35 years, atherogenic dyslipidemia frequently occurs in the absence of other metabolic syndrome risk factors.