Socio-economic factors and rheumatic fever occurrence. Differences between patients with and without frequent sore throat

One hundred and fourty-eight rheumatic fever patients and 444 controls matched by age, sex and place of residence, were interviewed about socio-economic and some other variables. Socio-economic factors recognized as risk factors for rheumatic fever (flat dampness, more than 2 persons per room, sleeping in bed with other person, low education of mother and undernourishment) were of lesser importance for persons with frequent sore throat in comparison to persons without frequent sore throat. According to the results obtained it seems that there is positive connection between host's propensity to clinical manifestation of throat infection and manifestation of rheumatic fever. The lesser susceptibility the more additional factors are needed for Rheumatic Fever to occur. The relative importance of socio-economic factors in rheumatic fever occurrence depends on host's susceptibility to infection.     

Pulmonary Tuberculosis Incidence and Risk Factors in Rural Areas of China: A Cohort Study

The incidence of tuberculosis (TB) and its risk factors in China remains unclear. This study examined TB incidence and relative risk factors in rural areas of China. Participants (n = 177,529) were recruited in Xiangtan County (in the central area of China) and in Danyang County (in the eastern area of China) in 2009 and a followed-up study was conducted for one year. The incidence density of pulmonary TB and smear-positive TB were 91.6 (95% CI: 78.7, 106.0) per 100,000 person-year and 36.7 (95% CI: 33.1, 52.4) per 100,000 person-year respectively in Xiangtan, and 47.3 (95% CI: 38.2, 57.5) per 100,000 person-year and 22.7 (95% CI: 16.5, 30.8) per 100,000 person-year in Danyang. The medical history of TB was associated with TB, with the relative risk (RR) of 7.00 (95% CI: 2.76, 17.18) in Xiangtan and that of 31.08 (95% CI: 13.22, 73.10) in Danyang. The association between TB and per capita living space over median was found in Xiangtan, with the RR of 1.86 (95% CI: 1.15, 3.01). No association was found between TB and the insurance status, the contact history with TB, the history of diabetes, smoking, or per capita annual income. The host genetic susceptibility, and social factors such as education and income could be considered in future studies.     

Perinatal mortality in eastern Uganda: a community based prospective cohort study

Background

To achieve a child mortality reduction according to millennium development goal 4, it is necessary to considerably reduce neonatal mortality. We report stillbirth and early neonatal mortality risks as well as determinants of perinatal mortality in Eastern Uganda.

Methods

A community-based prospective cohort study was conducted between 2006 and 2008. A total of 835 pregnant women were followed up for pregnancy outcome and survival of their children until 7 days after delivery. Mother''s residence, age, parity, bed net use and whether delivery took place at home were included in multivariable regression analyses to identify risk factors for perinatal death.

Results

The stillbirth risk was 19 per 1,000 pregnancies and the early neonatal death risk 22 per 1,000 live births. Overall, the perinatal mortality risk was 41 [95%CI: 27, 54] per 1,000 pregnancies. Of the deaths, 47% followed complicated deliveries and 24% preterm births. Perinatal mortality was 63/1,000 pregnancies among teenage mothers, 76/1,000 pregnancies among nulliparous women and 61/1,000 pregnancies among women delivering at home who, after controlling for potential confounders, had a 3.7 (95%CI: 1.8, 7.4) times higher perinatal mortality than women who gave birth in a health facility. This association was considerably stronger among nulliparous women [RR 8.0 (95%CI: 2.9, 21.6)] than among women with a previous live birth [RR 1.8 (95%CI: 0.7, 4.5)]. All perinatal deaths occurred among women who did not sleep under a mosquito net. Women living in urban slums had a higher risk of losing their babies than those in rural areas [RR: 2.7 (95%CI: 1.4, 5.3)].

Conclusion

Our findings strengthen arguments for ensuring that pregnant women have access to and use adequate delivery facilities and bed nets.     

Distance from Home to Study Clinic and Risk of Follow-Up Interruption in a Cohort of HIV-1-Discordant Couples in Nairobi, Kenya

Background

Longitudinal studies of HIV-1-infected individuals or those at risk of infection are subject to missed study visits that may have negative consequences on the care of participants and can jeopardize study validity due to bias and loss of statistical power. Distance between participant residence and study clinic, as well as other socioeconomic and demographic factors, may contribute to interruptions in patient follow-up.

Methods

HIV-1-serodiscordant couples were enrolled between May 2007 and October 2009 and followed for two years in Nairobi, Kenya. At baseline, demographic and home location information was collected and linear distance from each participant’s home to the study clinic was determined. Participants were asked to return to the study clinic for quarterly visits, with follow-up interruptions (FUI) defined as missing two consecutive visits. Cox proportional hazards regression was used to assess crude and adjusted associations between FUI and home-to-clinic distance, and other baseline characteristics.

Results

Of 469 enrolled couples, 64% had a female HIV-1-infected partner. Overall incidence of FUI was 13.4 per 100 person-years (PY), with lower incidence of FUI in HIV-1-infected (10.8 per 100 PY) versus -uninfected individuals (16.1 per 100 PY) (hazard ratio [HR] = 0.66; 95% confidence interval [CI]: 0.50, 0.88). Among HIV-1-infected participants, those living between 5 and 10 kilometers (km) from the study clinic had a two-fold increased rate of FUI compared to those living <5 km away (HR = 2.17; 95% CI: 1.09, 4.34). Other factors associated with FUI included paying higher rent (HR = 1.67; 95% CI: 1.05, 2.65), having at least primary school education (HR = 1.96; 95% CI: 1.02, 3.70), and increased HIV-1 viral load (HR = 1.23 per log₁₀ increase; 95% CI: 1.01, 1.51).

Conclusions

Home-to-clinic distance, indicators of socioeconomic status, and markers of disease progression may affect compliance with study follow-up schedules. Retention strategies should focus on participants at greatest risk of FUI to ensure study validity.     

Determinants of adolescent pregnancy in an urban area in Turkey: a population-based case-control study

The aim of this study was to determine the degree to which socioeconomic status is a risk factor for first birth at age 19 or younger in married women in an urban area of Turkey. The research was a population-based case-control study. The study group comprised all married and pregnant women aged 15-19 (adolescent pregnancies) attending primary care centres (144 subjects). Married women between 20 and 29 years of age, experiencing their first pregnancy (adult pregnancies), were determined as the control group (144 subjects). A questionnaire was completed for each subject during face-to-face interviews. Adolescent pregnancy was more frequent in women from families with a low socioeconomic status, as determined by occupation (class) and income; both were associated with adolescent pregnancy. Multiple logistic regression analysis identified seven factors associated with adolescent pregnancy: exposure to violence within the family prior to marriage; families partially opposed or unopposed to adolescent marriage; secondary school or lower education level; lack of social security; living in houses in which the number of persons per room was over 1; unemployed women; and having sisters with a history of adolescent pregnancy.     

Environmental effects on skeletal versus dental development: Using a documented subadult skeletal sample to test a basic assumption in human osteological research

This study examines the relationship between measures of skeletal and dental development and socioeconomic factors in a 20th century documented skeletal sample of children from Portugal. The skeletons are of known sex and chronological age, and include other biographic data, such as cause of death. Growth in the length of the long bone is used as a measure of skeletal growth, and schedules of tooth formation are used as a measure of dental development. These two measures of physiological age were compared to chronological age, to assess growth and developmental status. Socioeconomic indicators were obtained from the supporting documentation, and include the occupation of the father and the place of residence, which were used to build a socioeconomic classification based on two groups, one of low and the other of high socioeconomic status. Growth and development status was then compared in these two groups. Results show that socioeconomic differences are much more pronounced in skeletal growth than in dental development. This largely supports the assertion that dental development is buffered against environmental factors relative to skeletal development. However, in this study, skeletal maturation could not be assessed, and findings indicate that dental development can show significant delays at the lower end of the socioeconomic gradient.     

Ecological and socio-economic factors affecting extinction risk in parrots

Parrots (Psittaciformes) are among the most threatened bird orders with 28 % (111 of 398) of extant species classified as threatened under IUCN criteria. We confirmed that parrots have a lower Red List Index (higher aggregate extinction risk) than other comparable bird groups, and modeled the factors associated with extinction risk. Our analyses included intrinsic biological, life history and ecological attributes, external anthropogenic threats, and socio-economic variables associated with the countries where the parrot species occur, while we controlled for phylogenetic dependence among species. We found that the likelihood of parrot species being classified as threatened was less for species with larger historical distribution size, but was greater for species with high forest dependency, large body size, long generation time, and greater proportion of the human population living in urban areas in the countries encompassing the parrots’ home ranges. The severity of extinction risk (from vulnerable to critically endangered) was positively related to the per capita gross domestic product (GDP) of the countries of occurrence, endemism to a single country, and lower for species used as pets. A disproportionate number of 16 extinct parrot species were endemic to islands and single countries, and were large bodied, habitat specialists. Agriculture, hunting, trapping, and logging are the most frequent threats to parrots worldwide, with variation in importance among regions. We use multiple methods to rank countries with disproportionately high numbers of threatened parrot species. Our results promote understanding of global and regional factors associated with endangerment in this highly threatened taxonomic group, and will enhance the prioritization of conservation actions.     

Length of residence and obesity risk among North African immigrant women in Italy

Obesity is one of the major risks for chronic health conditions. Immigrants from low- and middle-income to high-income countries show a tendency to weight gain, with the country of origin, lifestyle habits, socioeconomic status and length of residence as the main factors involved. Thus, the aim of this study was to analyze the association between fat distribution and obesity with length of residence and other socio-demographic variables in a sample of North African women migrated to Italy. Socio-demographic variables were collected by structured face-to-face interview. For the assessment of weight status and body composition, various anthropometric traits were directly measured by an expert anthropometrist. Data were analyzed using ANCOVA adjusted for age to test the differences between length of residence (divided into three groups) and logistic regression models adjusted for covariates to test the association between overweight and/or obesity and length of residence. Significant differences between the three groups were observed in waist circumference (p = 0.004), waist-to-hip ratio (p = 0.001), and upper arm muscularity (p = 0.025), with higher values in those with longer duration of residence. In the crude logistic regression model length of residence resulted positively associated with obesity with the odds of being obese increased by 2.4 times in long term immigrants [OR 2.364 (0.766; 7.296)]. After adjusting for covariate the association remained significant [OR 3.584 (0.779; 16.480)], and being poorly educated [OR 5.737 (0.641; 51.363)], unemployed [OR 6.892 (0.940; 50.528)] and not practicing regular physical activity [OR 17.736 (1.569; 200.418)] increased the odds ratio of being obese.In conclusion, length of residence, socioeconomic status, and physical activity were significantly correlated with obesity, with a longer duration of residence being positively associated with central fat adiposity and upper arm muscle area in North African migrant women.     

Epidemiological Characterization and Risk Factors of Allergic Rhinitis in the General Population in Guangzhou City in China

The prevalence of allergic rhinitis (AR) in China has increased with an apparent geographic variation. The current study aims to investigate the AR prevalence/classification, diagnosis/treatment conditions, trigger factors, and risk factors in the general population of Guangzhou, the third biggest city in China. A cross-sectional survey was performed in the citizens in Guangzhou from December 2009 to March 2010 by using a stratified multistage cluster sampling method. All subjects were asked to complete a comprehensive questionnaire via a face to face interview. A total of 9,899 questionnaires were valid. The prevalence rate of AR in the general population of Guangzhou was 6.24%, with a significant higher prevalence in urban area (8.32%) versus rural area (3.43%). Among the AR subjects, most (87%) were diagnosed with intermittent AR and 87% suffered from moderate-severe symptoms. High percentages of the AR patients did not have previously physician-based diagnosis (34%) or specific medical treatment (55%). Morning time, winter season, and cold air were the most common trigger factors of AR. Family history of AR, current living place, living place during babyhood, smoking, home renovation, and pet ownership were the significant risk factors associated with AR prevalence in the population. The study demonstrated comprehensive epidemiological and clinical information about the AR in Guangzhou population. Change of living environment and lifestyles had strong impacts on the prevalence of AR. Public health policies should help the patients benefit from a proper diagnosis/treatment and specifically target the local risk factors, in order to control the AR incidence.     

Incidence of nonvalvular atrial fibrillation and oral anticoagulant prescribing in England, 2009 to 2019: A cohort study

BackgroundAtrial fibrillation (AF) is an important risk factor for ischaemic stroke, and AF incidence is expected to increase. Guidelines recommend using oral anticoagulants (OACs) to prevent the development of stroke. However, studies have reported the frequent underuse of OACs in AF patients. The objective of this study is to describe nonvalvular atrial fibrillation (NVAF) incidence in England and assess the clinical and socioeconomic factors associated with the underprescribing of OACs.Methods and findingsWe conducted a population-based retrospective cohort study using the UK Clinical Practice Research Datalink (CPRD) database to identify patients with NVAF aged ≥18 years and registered in English general practices between 2009 and 2019. Annual incidence rate of NVAF by age, deprivation quintile, and region was estimated. OAC prescribing status was explored for patients at risk for stroke and classified into the following: OAC, aspirin only, or no treatment. We used a multivariable multinomial logistic regression model to estimate relative risk ratios (RRRs) and 95% confidence intervals (CIs) of the factors associated with OAC or aspirin-only prescribing compared to no treatment in patients with NVAF who are recommended to take OAC. The multivariable regression was adjusted for age, sex, comorbidities, socioeconomic status, baseline treatment, frailty, bleeding risk factors, and takes into account clustering by general practice. Between 2009 and 2019, 12,517,191 patients met the criteria for being at risk of developing NVAF. After a median follow-up of 4.6 years, 192,265 patients had an incident NVAF contributing a total of 647,876 person-years (PYR) of follow-up. The overall age-adjusted incidence of NVAF per 10,000 PYR increased from 20.8 (95% CI: 20.4; 21.1) in 2009 to 25.5 (25.1; 25.9) in 2019. Higher incidence rates were observed for older ages and males. Among NVAF patients eligible for anticoagulation, OAC prescribing rose from 59.8% (95% CI: 59.0; 60.6) in 2009 to 83.2% (95% CI: 83.0; 83.4) in 2019. Several conditions were associated with lower risk of OAC prescribing: dementia [RRR 0.52 (0.47; 0.59)], liver disease 0.58 (0.50; 0.67), malignancy 0.74 (0.72; 0.77), and history of falls 0.82 (0.78; 0.85). Compared to white ethnicity, patients from black and other ethnic minorities were less likely to receive OAC; 0.78 (0.65; 0.94) and 0.76 (0.64; 0.91), respectively. Patients living in the most deprived areas were less likely to receive OAC 0.85 (0.79; 0.91) than patients living in the least deprived areas. Practices located in the East of England were associated with higher risk of prescribing aspirin only over no treatment than practices in London (RRR 1.22; 95% CI 1.02 to 1.45). The main limitation of this study is that these findings depends on accurate recording of conditions by health professionals and the inevitable residual confounding due to lack of data on certain factors that could be associated with under-prescribing of OACs.ConclusionsThe incidence of NVAF increased between 2009 and 2015, before plateauing. Underprescribing of OACs in NVAF is associated with a range of comorbidities, ethnicity, and socioeconomic factors, demonstrating the need for initiatives to reduce inequalities in the care for AF patients.

Alyaa Ajabnoor and co-workers study incidence of non-valvular atrial fibrillation in England and apparent inequalities in care.     

Living in Sofia is associated with a risk for antibiotic resistance in Helicobacter pylori: a Bulgarian study

The aim of the retrospective study was to evaluate geographic regions and residence places as possible risk factors for primary Helicobacter pylori antibiotic resistance in Bulgaria. Data from Sofia region, exhibiting the highest living density, were compared to those from other residence places. In total, 588 H. pylori strains from untreated adults who filled a questionnaire were evaluated. Strain susceptibility was assessed by a breakpoint susceptibility test. Resistance rates to metronidazole and clarithromycin have been found to increase, and that to tetracycline has been found to decrease over years. Clarithromycin resistance was 1.7-fold higher in Sofia inhabitants (23.5 %) than elsewhere (13.8 %) and 4.7-fold higher than that in villages (5.0 %). Moreover, the clarithromycin resistance rate was 2.6-fold lower in northern region (8.2 %) than in southern region (21.7 %). On multivariate analysis, sex and residence place were independent predictors for metronidazole resistance. Men were at lower risk for metronidazole resistance compared with women [odds ratio (OR) 0.703; 95 % confidence interval (CI) 0.499–0.990]. Importantly, Sofia inhabitants were at higher risk for the resistance compared with those living elsewhere (OR 1.453; 95 % CI 1.009–2.093). In conclusion, living in Sofia was associated with a risk for antibiotic resistance in H. pylori-positive adults. Living density could be associated with H. pylori resistance rates.     

HBs antigen and antibody in Barcelona]

The frequency of HBs antigen and antibody has been studied among three populations living in Spain: blood donors, hospital staff, renal deficient hemodialyzed patients. Total results and those given with reference to age, sex, place of birth and residence are compared to each other and to those obtained for populations living in Languedoc.     

Seroprevalence of Helicobacter pylori and Length of Stay in a Nursing Home

Background. Helicobacter pylori infection appears to be contracted mainly in childhood, and it is associated with disadvantaged socioeconomic conditions, overcrowding, and living in institutions. In this study we determined the seroprevalence of H. pylori among elderly patients (age ≥ 70 years) admitted to a major medical center in Israel, and studied the relationship between seroprevalence of H. pylori and the duration of stay in a nursing home prior to the admission.
Patients and Methods. Whole blood from 182 consecutive patients hospitalized at the Rabin Medical Center was tested for the presence of anti- H. pylori IgG using Helisal Rapid Blood Test kit (Cortecs Diagnostics). Multivariate logistic regression analysis was used to study the relation between H. pylori seropositivity and possible predictive factors such as age, gender and duration of stay in a nursing home.
Results. Of the 182 patients included in the study, 80 (44%) were living in nursing homes (NH) and 102 (56%) were living in their own homes (H) prior to admission. Subjects that stayed in nursing homes for more than 15 months were significantly more likely to be seropositive than subjects with a shorter duration of stay (84% and 63% respectively, p = 0.03). Using a multivariate logistic regression analysis on both the NH group and the whole group, seropositivity was found to be significantly associated with duration of stay in a nursing home (  p = 0.03 and p = 0.01 respectively). Seropositivity was not associated with age in either group.
Conclusions. Living in a nursing home is associated with increased risk for H. pylori infection in the elderly. There is a strong correlation between the duration of stay in a nursing home and the prevalence of H. pylori infection.     

Socioeconomic determinants of rates of consultation in general practice based on fourth national morbidity survey of general practices.

OBJECTIVE--To identify the socioeconomic determinants of consultation rates in general practice. DESIGN--Analysis of data from the fourth national morbidity survey of general practices (MSGP4) including sociodemographic details of individual patients and small area statistics from the 1991 census. Multilevel modelling techniques were used to take account of both individual patient data and small area statistics to relate socioeconomic and health status factors directly to a measure of general practitioner workload. RESULTS--Higher rates of consultations were found in patients who were classified as permanently sick, unemployed (especially those who became unemployed during the study year), living in rented accommodation, from the Indian subcontinent, living with a spouse or partner (women only), children living with two parents (girls only), and living in urban areas, especially those living relatively near the practice. When characteristics of individual patients are known and controlled for the role of "indices of deprivation" is considerably reduced. The effect of individual sociodemographic characteristics were shown to vary between different areas. CONCLUSIONS--Demographic and socioeconomic factors can act as powerful predictors of consultation patterns. Though it will always be necessary to retain some local planning discretion, the sets of coefficients estimated for individual level factors, area level characteristics, and for practice groupings may be sufficient to provide an indicative level of demand for general medical services. Although the problems in using socioeconomic data from individual patients would be substantial, these results are relevant to the development of a resource allocation formula for general practice.     

Fertility desires of Yoruba couples of South-western Nigeria

Using the matched wife-husband (763) sample from the data collected from Ogbomoso and Iseyin towns in Oyo State, Nigeria, this paper examines factors associated with couples' fertility intention. The analysis used logistic regression models for predicting the effects of selected socioeconomic background characteristics on a couple's fertility intention. Results indicate high levels of concurrence among husbands and wives on fertility intention. Where differences exist, husbands are more pronatalists than their wives. About 87% of pairs of partners reported similar fertility preferences. Of these couples, 59.5% wanted more children while only 27.8% reported otherwise. The logistic regression models indicated that a couple's fertility intention was associated with age, education, place of residence, frequency of television-watching and number of living children. Therefore, programme interventions aimed at promoting fertility reduction in Nigeria should convey fertility regulation messages to both husbands and wives.     

Maternal diseases and isolated orofacial clefts in Hungary

BACKGROUND: Isolated orofacial clefts (OFCs) are likely to be caused by gene-environment interaction; therefore, the objective of the current study was to evaluate the possible association between all maternal diseases during pregnancy and isolated cleft lip with or without cleft palate (CL+/-CP) and posterior cleft palate (PCP) in the offspring. METHODS: The database of the large population-based Hungarian Case-Control Surveillance of Congenital Abnormalities, 1980-1996, was evaluated. The database includes 1374 cases with isolated CL+/- CP and 601 with PCP, plus 38,151 matched population controls (without defects) and 20,868 patient controls with other defects. Data collection was based on prospective medical records, retrospective maternal data via a self-reported questionnaire, and home visits of nonresponding families. RESULTS: An increased risk for isolated CL+/- CP was found for children born to mothers with influenza, common cold, orofacial herpes, and gastroenteritis during pregnancy. Risk for isolated PCP was increased in children of mothers with influenza, sinusitis, and bronchitis. Among chronic maternal diseases, epilepsy and angina pectoris showed a higher prevalence in the mothers of children born with isolated OFCs (cases). CONCLUSIONS: Some maternal diseases are risk factors for the pathogenesis of isolated OFCs. It is worth considering the prevention of possible harmful effects of influenza by vaccination during the expected epidemic period.     

Vitamin D Deficiency and Its Predictors in a Country with Thirteen Months of Sunshine: The Case of School Children in Central Ethiopia

Studies examining vitamin D status among children living in sunny climates indicated that children did not receive adequate vitamin D, however, this has not been looked at among children living in Ethiopia. In this study, we determined vitamin D deficiency and its predictors among school children aged 11–18 years, examining circulating 25-hydroxy vitamin D [25(OH)D]. The school-based cross-sectional study was conducted in schools in Adama Town (n = 89) and in rural Adama (n = 85) for a total sample of 174. Students were randomly selected using multi-stage stratified sampling method from both settings. Socioeconomic status of parents and demographic, anthropometric, sun exposure status and blood 25(OH)D levels were obtained. Vitamin D deficiency, defined as circulating levels of 25(OH)D <50 nmol/L, was found in 42% of the entire study participants. Prevalence of deficiency was significantly higher among students in urban setting compared to rural (61.8% vs 21.2%, respectively, p<0.001). After controlling for potential confounders using multivariable logistic regression model, duration of exposure to sunlight, amount of body part exposed to sunlight, place of residence, maternal education, body fatness, having TV/computer at home and socioeconomic status were significant predictors of vitamin D deficiency. The findings suggest that Vitamin D deficiency was prevalent in healthy school children living both in urban and rural areas of a country with abundant year round sunshine providing UVB, with the prevalence of deficiency being significantly higher among urban school children who were less exposed to sunlight. Behaviour change communication to enhance exposure to ultraviolet light is critical to prevent vitamin D deficiency in tropical country like Ethiopia. Further study is required to assess the deleterious effect of its deficiency on bone mineral homeostasis of growing children in Ethiopia during their most critical period of bone development.     

Household and community socioeconomic influences on early childhood malnutrition in Africa

This paper uses multilevel modelling and Demographic and Health Survey data from five African countries to investigate the relative contributions of compositional and contextual effects of socioeconomic status and place of residence in perpetuating differences in the prevalence of malnutrition among children in Africa. It finds that community clustering of childhood malnutrition is accounted for by contextual effects over and above likely compositional effects, that urban-rural differentials are mainly explained by the socioeconomic status of communities and households, that childhood malnutrition occurs more frequently among children from poorer households and/or poorer communities and that living in deprived communities has an independent effect in some instances. This study also reveals that socioeconomic inequalities in childhood malnutrition are more pronounced in urban centres than in rural areas.     

Case-control study of leukaemia among young people near La Hague nuclear reprocessing plant: the environmental hypothesis revisited.

OBJECTIVE: To investigate the association between childhood leukaemia and established risk factors or other factors related to La Hague nuclear waste reprocessing plant. DESIGN: Case-control study. SETTING: Area within a 35 km radius of La Hague, Normandy, France. SUBJECTS: Twenty seven cases of leukaemia diagnosed during the period 1978-93 in people aged under 25 years and 192 controls matched for sex, age, place of birth, and residence at time of diagnosis. MAIN OUTCOME MEASURES: Antenatal and postnatal exposure to x rays and viral infections, occupational exposure of parents (particularly ionising radiation), living conditions, lifestyle of parents and children. RESULTS: Increased trends were found for use of local beaches by mothers and children (P < or = 0.01); relative risks 2.87 (95% confidence intervals 1.05 to 8.72) and 4.49 (1.52 to 15.23) when categories were aggregated in two levels (more or less than once a month). Consumption of local fish and shellfish also showed an increased trend (P 0.01); relative risk 2.66 (0.91 to 9.51) when categories were grouped in two levels (more or less than once a week). A relative risk of 1.18 a year (1.03 to 1.42) was observed for length of residence in a granite-built house or in a granitic area. No association was shown with occupational radiation exposure in parents. CONCLUSIONS: There is some convincing evidence in childhood leukaemia of a causal role for environmental radiation exposure from recreational activities on beaches. New methods for identifying the environmental pathways, focusing on marine ecosystems, are warranted.