Quantifying the increase in average human heterozygosity due to urbanisation.

The human population is undergoing a major transition from a historical metapopulation structure of relatively isolated small communities to an outbred structure. This process is predicted to increase average individual genome-wide heterozygosity (h) and could have effects on health. We attempted to quantify this increase in mean h. We initially sampled 1001 examinees from a metapopulation of nine isolated villages on five Dalmatian islands (Croatia). Village populations had high levels of genetic differentiation, endogamy and consanguinity. We then selected 166 individuals with highly specific personal genetic histories to form six subsamples, which could be ranked a priori by their predicted level of outbreeding. The measure h was then estimated in the 166 examinees by genotyping 1184 STR/indel markers and using two different computation methods. Compared to the value of mean h in the least outbred sample, values of h in the remaining samples increased successively with predicted outbreeding by 0.023, 0.038, 0.058, 0.067 and 0.079 (P<0.0001), where these values are measured on the same scale as the inbreeding coefficient (but opposite sign). We have shown that urbanisation was associated with an average increase in h of up to 0.08-0.10 in this Croatian metapopulation, regardless of the method used. Similar levels of differentiation have been described in many populations. Therefore, changes in the level of heterozygosity across the genome of this magnitude may be common during isolate break-up in humans and could have significant health effects through the established genetic mechanism of hybrid vigour/heterosis.

Effects of isolation and inbreeding on human quantitative traits: an example of biochemical markers of hemostasis and inflammation.

Isolation is a known force in evolutionary biology and one of the main factors in speciation. One of the main consequences of severe isolation is reduced mate choice, which results in the occurrence of inbreeding as a result of isolation. We investigated the effects of individual genome-wide heterozygosity measured as the multilocus heterozygosity (MLH) on biochemical markers of hemostasis and inflammation in 1,041 individuals from the island of Vis, Croatia, where inbreeding is prevalent and a wide range of variation in the genome-wide heterozygosity is expected. Assessment of individual genome-wide heterozygosity was based on genome-wide scans using 800 microsatellite (STR) and 317,503 single nucleotide (SNP) polymorphic markers in each examinee. In addition, for each examinee we defined a personal genetic history (PGH) based on genealogical records. The association between PGH and MLH and fibrinogen, D-dimer (Dd), von Willebrand factor (vWF), tissue plasminogen activator (tPA), and C-reactive protein (CRP) was performed with a mixed model, controlling for possible confounding effects. PGH was a significant predictor only for tPA (P < 0.001), whereas neither of the two MLH measures exhibited significant association with any of the investigated traits. The effects of individual genome-wide heterozygosity are most likely expressed in highly polygenically determined traits or in traits that are mediated by rare and recessive genetic variants. Weak associations between PGH and MLH and markers of hemostasis and inflammation suggest that their genetic control may not be highly polygenic and that they could be promising targets for genetic association studies.

The prevalence of allergic diseases among Croatian school children according to the ISAAC Phase One questionnaire.

BACKGROUND: The prevalence of asthma and allergic diseases in children has been increasing worldwide over the past decades. The ISAAC Phase I results supplies valuable information on the worldwide variations in the prevalence of these diseases. Although ISAAC Phase I was completed in 56 countries, not all regions of Croatia were covered. Because of Croatia's high regional diversity, the aim was to explore the prevalence of asthma, allergic rhinitis/rhinoconjuctivitis, and atopic eczema symptoms in the Medimurje region in northern Croatia and compare the results with data from other regions in Croatia and other countries. MATERIAL/METHODS: The study was undertaken between January and April 2005 among 12- to 14-year-old children in 27 elementary schools. Data were collected using the standardized ISAAC written and asthma video questionnaires. RESULTS: A total of 3111 children participated in the study, with a participation rate of 94.33%. 27.6% of the children had symptoms of allergic diseases at some time in their life. Estimated lifetime (ever) prevalence of symptoms were: wheezing 11.86%, allergic rhinitis symptoms 12.21%, and atopic dermatitis symptoms 7.01%. Estimated 12-month prevalence rates were: wheezing 5.11%, allergic rhinitis symptoms 10.87%, allergic rhinoconjunctivitis 7.14%, and atopic dermatitis symptoms 5.34%. CONCLUSIONS: Compared with previous studies conducted in other Croatian regions (the city of Zagreb and a northern Adriatic region) using similar methods, the prevalence of asthma and allergic rhinitis was lower than in the northern Adriatic region but comparable with that in the city of Zagreb, and of atopic dermatitis symptoms in the same range.

Micro-scale socioeconomic inequalities and health indicators in a small isolated community of Vis Island, Croatia.

AIM: To investigate whether socioeconomic inequalities at a micro-scale, through their effect on major health risk factors and other health indicators, contribute to health status in an isolated island population with demonstrated reduced genetic and environmental variability. METHODS: This cross-sectional study was performed in 2003 and 2004 in the adult population of the island of Vis, Croatia. Participants were recruited from the electoral register. A total of 1024 participants were included in the study, which represented a response rate of approximately 70%. The level of education and household socioeconomic status were used as the socioeconomic status indicators. Associations of these indicators with hypertension, obesity, hyperlipidaemia, smoking, diet indicators, and supplementary vitamins and calcium intake were investigated. Data analysis was performed by multivariate methods. RESULTS: Age and gender were most commonly associated with the presence of major health risk factors. Level of education did not show significant association with any of the investigated risk factors, supplements intake, or with dietary habits. Household socioeconomic status was significantly associated only with excessive alcohol intake (logistic regression odds ratio [OR], 1.85; 95% confidence interval [CI], 1.12-3.07, P=0.016), obesity (OR, 1.78; 95% CI, 1.13-2.81 P=0.013), and high-fat diet (multiple linear modeling F=2.75, P=0.042). CONCLUSION: In isolated communities, socioeconomic stratification may be a less important health determinant than in large general populations, making these populations favorable resource for biomedical research into other health risk factors.

Metabolic syndrome in a metapopulation of Croatian island isolates.

AIM: To investigate the prevalence and factors associated with the metabolic syndrome in 9 isolated populations on Adriatic islands, Croatia, and in the group of immigrants to these islands. METHODS: Random samples of 100 inhabitants from each village and 101 immigrants were collected during 2002 and 2003. Bivariate and multivariate methods were used in data analysis. Age, gender, village, diet, smoking habits, physical activity, education, occupational class, and personal genetic history (a pedigree-based estimate of the individual genome-wide heterozygosity level) were used as independent variables in logistic regression. RESULTS: A total of 343 (34%) examinees met criteria of the metabolic syndrome diagnosis, with significant differences in the prevalence among villages (P=0.002). Metabolic syndrome was most frequently detected on Mljet island (53%), where all examinees exhibited fasting plasma glucose over 6.1 mmol/L. Examinees with metabolic syndrome were significantly older than those without it (median age 60.0 vs 53.0; P<0.001). Women were more frequently diagnosed than men (39% vs 28%; P<0.001). The highest prevalence of the metabolic syndrome was found in the autochthonous group, whereas the lowest proportion was recorded in the admixed group (39% vs 21%, respectively, P=0.017). However, only age (odds ratio [OR], 1.06; 95% confidence intervals [CI], 1.03-1.08) and having a university degree (OR, 0.18; 95% CI 0.04-0.92) were significantly associated with metabolic syndrome in the regression model. CONCLUSION: Metabolic syndrome was not associated with pedigree-based individual genome-wide heterozygosity estimate, after controlling for a number of confounding factors. More precise marker based genomic measures are needed to provide a clear answer whether metabolic syndrome development is influenced by the population genetic structure.

Effects of inbreeding, endogamy, genetic admixture, and outbreeding on human health: a (1001 Dalmatians) study.

AIM: (1001 Dalmatians) research program collects biomedical information from multiple small isolated populations ((metapopulation)) on Adriatic islands, Croatia, and investigates health effects of human population isolation, inbreeding, admixture, and outbreeding. METHODS: We collected random samples of 100 individuals from 9 island settlements and an additional sample of 101 immigrants to the islands, pooled from all study populations. According to their personal genetic histories, the examinees were categorized as inbred, autochthonous, admixed, and outbred. A total of 76 inbred individuals from a total sample of 1001 examinees were matched to 76 autochthonous, 76 admixed, and 76 outbred controls by gender, age (+/-5 years), village of residence, education, and socio-economic status. We investigated the effects of presumed individual genome-wide heterozygosity predicted from personal genetic histories on the following 10 traits: systolic and diastolic blood pressure, body mass index, high and low density lipoproteins and total cholesterol, triglycerides, uric acid, creatinine, and blood glucose. RESULTS: Personal genetic history significantly affected systolic blood pressure (Spearman rho=0.157, P=0.006), while the effect on cholesterol (rho=0.105, P=0.069), and high density lipoprotein cholesterol (rho=0.104, P=0.071) was suggestive. Admixed individuals and immigrants consistently showed values associated with lower health risk. When inbred and autochthonous samples were merged and compared with the admixed and outbred samples to increase the power of the study, the effects on the three traits above and also on body mass index and diastolic blood pressure became statistically significant. The medians for all 10 medically relevant traits in inbred and autochthonous group, with lower values of presumed individual genome-wide heterozygosity, were less favorable in terms of health. CONCLUSION: The combined effects of founder effect, genetic drift, and inbreeding can increase the frequency of detrimental rare variants in human metapopulations, leading to overall worsening of population health, whereas admixture and outbreeding appear to have the opposite effect.

Risk factors in urban road traffic accidents.

INTRODUCTION: The urban road traffic accident (RTA) risks for the city of Zagreb, Croatia, from 1999 through 2000 were analyzed with the aim of reducing the increasing injury incidence. METHOD: Simple and bivariate analysis using chi(2), odds ratio, and confidence interval of 95% was used to determine risks in three outcome groups: killed, severely, and mildly injured. RESULTS: There were 528 RTA victims consisting of 260 severely, 213 mildly injured, and 55 killed at the scene of an accident and during transportation. More fatal accidents occurred during night hours (OR=3.78; 95% CI, 2.08-6.85), on urban road links (OR=2.33; 95% CI, 1.30-4.19), and at exceeding speed limit (OR=2.56; 95% CI, 1.43-4.61). More people were injured than killed on urban junctions (OR=5.27; 95% CI, 2.21-12.57). The highest combined risk of dying or being severely injured was found in males, driving at excessive speed, on urban links, and during bad visibility (OR=16.15; 95% CI, 3.901-66.881). CONCLUSION: These results will influence the urban traffic police enforcement measures, which will change inappropriate behavior of drivers and protect the least experienced road users.

Seasonality of births in Croatia.

The aim of this paper was to investigate seasonal fluctuations of the number of births in Croatia. Vital registration data from the years 1970-2002 was used for analysis of the quarterly data (from the years 1970-1997), and monthly data (from the years 1998-2002). Both data sets were smoothed, using seasonal variation removal for quarterly data, and T4253H smoothing for monthly data. Edwards test and Ratchet circular scan tests were used in analysis. The results showed an increase in the summer birth proportion and decrease in the spring birth proportion, distorted during the wartime period (1991-1995). Monthly analysis reveals highest birth proportion in Croatia during July-September period, with peak date moving towards the end of summer, and reaching stability in the beginning of September during the years 2000-2002. This presumes highest conception rate during the beginning of the Christmas holiday season. Secondary peak in January was found in some years, which presumably sets second period of increased conception rate into the Easter holiday season, supporting the observation of the holiday-related birth peaks. Both quarterly and monthly data indicate a birth pattern that does not resemble either "European", or "American" seasonal pattern. Regional analysis showed lack of seasonality in the capital city of Zagreb and either intermittent or stable seasonality pattern in the rest of the country.

[Study of accidents in the Koprivnica area]. / Istrazivanje nesreca na koprivnickom podrucju.

The aim of this paper is to present injury incidence, risky population groups, circumstances and activities before the accident and injury mechanism in Koprivnica district (715 km2, 61,052 inhabitants). Data were taken from the Register which includes all population who were injured in this area. Register was located in surgical unit, general hospital in Koprivnica. During study period Jan 1, 1998-Jun 30, 2000 there were 4833 injured persons registered. Males had significantly higher injury incidence (40.9/1000) than females (23.8/1000) (P < 0.01). The highest incidence among male population was in the age 15-24 yrs. (66.3/1000) and among females in the age 0-14 yrs. (35.6/1000). The most risky time for accidents was on Saturday (18.7%) and at 12-18 p.m. (53.2%). The highest road traffic accident mortality was in older age (65 and over) (110.3/100,000) and the highest injury incidence was in younger age (15-24 yrs.) (3200.6/100,000). Regarding other accidents, the most risky place was around the house, in garden (26.6%). The most frequent injury mechanism for both genders is slipping (16.5%); in men follow cuts (12.8%) and being hit from the moving object (12.3%) and in women follow fall on (from) stairs (12.5%) and cuts (10.7%). The most frequent activity before an accident appears is unpaid work with tools, machines and other (15.7%). More detailed investigation on the local level makes possible suggesting more efficient injury prevention programs.

Youth and AIDS--a study of attitudes, knowledge, behavior and risks in the post-war Croatia.

According to the latest reports, the Eastern Europe currently exhibits the greatest relative increase in the number of newly registered HIV infections in the world. At the same time, Central Europe remains relatively spared from the epidemic, with reported rates significantly lower than those in both Eastern and Western Europe. Croatia geographically affiliates to Central Europe, but it has two specific potential risk factors in comparison to neighboring countries: recent War events and a summer season when immigration of large number of tourists from Central and Eastern Europe is expected. Therefore, it is critical to examine AIDS attitudes in young people, increase their knowledge, monitor their behavior and warn on risks in order to prevent larger spread of epidemics from Eastern Europe to Croatia. In this study, we report on a large related survey and education program among 17-year-old high school pupils that was conducted in years immediately following the War (1996-1999).

[The Mediterranean diet and occurrence of malignant tumors of the digestive system in the Croatian islands]. / Mediteranski nacin prehrane i ucestalost zlocudnih tumora probavnog sustava na hrvatskim otocima.

The aim of this study was to compare the age-standardised incidence rates of gastric bowel and pancreatic cancer between two regions of the Republic of Croatia: (1) five middle Dalmatian islands (Brac, Hvar, Korcula, Vis and Lastovo) with "Mediterranean" nutrition; (2) the control population of Koprivnicko-krizevacka County (KKC) with "continental" nutrition. The characterisation of nutrition habits in the two study regions revealed very significant differences. The newly registered cases of gastric, bowel and pancreatic cancer between 1986 and 1995 were retrieved from the Cancer Registry of Croatia. The resulting incidence rates were standardised to the standard world population using the method of direct standardisation. Age-standardised incidence rates in the islands in comparison to the control KKC population per 100,000 inhabitants were 17.2 vs. 39.4 (p < 0.001) in males with gastric cancer, 9.1 vs. 16.5 (p < 0.01) in females with gastric cancer, 34.5 vs. 31.4 (p > 0.05) in males with bowel cancer, 18.3 vs. 20.3 (p > 0.05) in females with bowel cancer, 5.5 vs. 9.0 (p < 0.05) in males with pancreatic cancer and 2.7 vs. 5.0 in females with pancreatic cancer (p < 0.05). Standardised incidence rates of gastric and pancreatic cancer in the island populations were significantly lower from the standardized Croatian average. The study showed that "Mediterranean" type of diet could have a protective effect against gastric and pancreatic cancer.