Population Attributable Risk Fraction Research Articles

Metabolic Syndrome and Mortality in Older Adults

The utility of metabolic syndrome (MetS) for predicting mortality among older adults, the highest-risk population, is not well established. In addition, few studies have compared the predictive utility of MetS to that of its individual risk factors. We evaluated relationships of MetS (as defined by the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults [Adult Treatment Panel III (ATPIII)], International Diabetes Foundation [IDF], and World Health Organization [WHO]) and individual MetS criteria with mortality between 1989 and 2004 among 4258 US adults 65 years or older and free of prevalent cardiovascular disease (CVD) in the Cardiovascular Health Study, a multicenter, population-based, prospective cohort. Total, CVD, and non-CVD mortality were evaluated. Cox proportional hazards models were used to estimate the mortality hazard ratio (relative risk [RR]) predicted by MetS. At baseline (mean age, 73 years), 31% of men and 38% of women had MetS (ATPIII). During 15 years of follow-up, 2116 deaths occurred. After multivariable adjustment, compared with persons without MetS, those with MetS had a 22% higher mortality (RR, 1.22; 95% confidence interval [CI], 1.11-1.34). Higher risk with MetS was confined to persons having elevated fasting glucose level (EFG) (defined as > or = 110 mg/dL [> or = 6.1 mmol/L] or treated diabetes mellitus) (RR, 1.41; 95% CI, 1.27-1.57) or hypertension (RR, 1.26; 95% CI, 1.15-1.39) as one of the criteria; persons having MetS without EFG (RR, 0.97; 95% CI, 0.85-1.11) or MetS without hypertension (RR, 0.92; 95% CI, 0.71-1.19) did not have higher risk. Evaluating MetS criteria individually, we found that only hypertension and EFG predicted higher mortality; persons having both hypertension and EFG had 82% higher mortality (RR, 1.82; 95% CI, 1.58-109). Substantially higher proportions of deaths were attributable to EFG and hypertension (population attributable risk fraction [PAR%], 22.2%) than to MetS (PAR%, 6.3%). Results were similar when we used WHO or IDF criteria, when we evaluated different cut points of each individual criterion, and when we evaluated CVD mortality. These findings suggest limited utility of MetS for predicting total or CVD mortality in older adults compared with assessment of fasting glucose and blood pressure alone.

Prospective meta-analysis of interleukin 1 gene complex polymorphisms confirms associations with ankylosing spondylitis

Objectives:The aim of the current study was to determine the contribution of interleukin (IL)1 gene cluster polymorphisms previously implicated in susceptibility for ankylosing spondylitis (AS) to AS susceptibility in different...

Erectile dysfunction prospectively associated with cardiovascular disease in the Dutch general population: results from the Krimpen Study

The possible relationship between erectile dysfunction and the later occurrence of cardiovascular disease while biologically plausible has been evaluated in only a few studies. Our objective is to determine the relation between ED as defined by a single question on erectile rigidity and the later occurrence of myocardial infarction, stroke and sudden death in a population-based cohort study. In Krimpen aan den IJssel, a municipality near Rotterdam, all men aged 50-75 years, without cancer of the prostate or the bladder, without a history of radical prostectomy, neurogenic bladder disease, were invited to participate for a response rate of 50%. The answer to a single question on erectile rigidity included in the International Continence Society male sex questionnaire was used to define the severity of erectile dysfunction at baseline. Data on cardiovascular risk factors at baseline (age smoking, blood pressure, total- and high-density lipoprotein cholesterol, diabetes) were used to calculate Framingham risk scores. During an average of 6.3 years of follow-up, cardiovascular end points including acute myocardial infarction, stroke and sudden death were determined. Of the 1248 men free of CVD at baseline, 258 (22.8%) had reduced erectile rigidity and 108 (8.7%) had severely reduced erectile rigidity. In 7945 person-years of follow-up, 58 cardiovascular events occurred. In multiple variable Cox proportional hazards model adjusting for age and CVD risk score, hazard ratio was 1.6 (95% confidence interval (CI): 1.2-2.3) for reduced erectile rigidity and 2.6 (95% CI: 1.3-5.2) for severely reduced erectile rigidity. The population attributable risk fraction for reduced and severely reduced erectile rigidity was 11.7%. In this population-based study, a single question on erectile rigidity proved to be a predictor for the combined outcome of acute myocardial infarction, stroke and sudden death, independent of the risk factors used in the Framingham risk profile.

Association Study of the Genetic Polymorphisms of the Transcription Factor 7-Like 2 (TCF7L2) Gene and Type 2 Diabetes in the Chinese Population

Genetic polymorphisms of the transcription factor 7-like 2 (TCF7L2) gene is one of the few validated genetic variants with large effects on the risk of type 2 diabetes in the populations of European ancestry. In this study, we aimed to explore the effect of the TCF7L2 polymorphisms in a Han Chinese population. We genotyped 20 single nucleotide polymorphisms (SNPs) across the TCF7L2 gene in 1,520 unrelated subjects from a Han Chinese population in Taiwan. The associations of SNPs and haplotypes with type 2 diabetes and linkage disequilibrium (LD) structure of the TCF7L2 gene were analyzed. The previously reported SNPs rs7903146 T- and rs12255372 T-alleles of the TCF7L2 gene were rare and were not associated with type 2 diabetes in a Chinese population, which may attribute to the low frequencies of these two SNPs. SNP rs290487 located in an LD block close to the 3' end of the gene was associated with type 2 diabetes (allele-specific P = 0.0021; permuted P = 0.03). The odds ratio was 1.36 for the CT genotype (95% CI 1.08-1.71; P = 0.0063) and 1.51 for the CC genotype (1.10 -2.07; P = 0.0085) compared with the TT genotype, corresponding to a population attributable risk fraction of 18.7%. The haplotypes composed of rs290487 were also significantly associated with type 2 diabetes (global P = 0.012). We identified a novel risk-conferring genetic variant of TCF7L2 for type 2 diabetes in a Chinese population. Our data suggested that the TCF7L2 genetic polymorphisms are major determinants for risk of type 2 diabetes in the Chinese population.

Severe Mental Illness and Risk of Sexual Offending in Men

To examine the comorbidity of severe mental illness with sexual offending in men. A case-control design was used to investigate psychiatric hospitalization and sexual offending. Data were obtained from Swedish national registers for crime, hospital discharge diagnoses (based on International Classification of Diseases revisions 9 and 10), demographic, and socioeconomic factors for the years 1988 through 2000. All male sexual offenders (N = 8495) in Sweden were included and compared with a random sample of male controls taken from the general population (N = 19,935). The population attributable risk fraction (the proportion of all sexual crimes throughout the study period that were committed by patients with a history of psychiatric hospitalization) was also estimated. After adjustment for demographic and socioeconomic confounders, sexual offenders were 6 times more likely to have a history of psychiatric hospitalization compared with the general population (OR = 6.3, 95% CI = 5.7 to 6.9). Sexual offenders were significantly more likely to have a severe mental illness than the general population, whether this was schizophrenia (OR = 4.8, 95% CI = 3.4 to 6.7), other psychoses (OR = 5.2, 95% CI = 3.9 to 6.8), or bipolar affective disorder (OR = 3.4, 95% CI = 1.8 to 6.4). The proportion of all sexual crimes committed by hospitalized psychiatric patients (the population attributable risk fraction) was 20.1%. The increased relative risk of psychiatric hospitalization and severe mental illness in sexual offenders is contrary to much expert opinion in the field. If these findings are replicated in other settings, policies in the criminal justice system regarding the assessment, management, and treatment of sexual offenders may need review.

The Population Impact of Severe Mental Illness on Violent Crime

This study aimed to determine the population impact of patients with severe mental illness on violent crime. Sweden possesses high-quality national registers for all hospital admissions and criminal convictions. All individuals discharged from the hospital with ICD diagnoses of schizophrenia and other psychoses (N=98,082) were linked to the crime register to determine the population-attributable risk of patients with severe mental illness to violent crime. The attributable risk was calculated by gender, three age bands (15-24, 25-39, and 40 years and over), and offense type. Over a 13-year period, there were 45 violent crimes committed per 1,000 inhabitants. Of these, 2.4 were attributable to patients with severe mental illness. This corresponds to a population-attributable risk fraction of 5.2%. This attributable risk fraction was higher in women than men across all age bands. In women ages 25-39, it was 14.0%, and in women over 40, it was 19.0%. The attributable risk fractions were lowest in those ages 15-24 (2.3% for male patients and 2.9% for female patients). The population impact of patients with severe mental illness on violent crime, estimated by calculating the population-attributable risk, varies by gender and age. Overall, the population-attributable risk fraction of patients was 5%, suggesting that patients with severe mental illness commit one in 20 violent crimes.

The Population Impact of Severe Mental Illness on Violent Crime

Objective: This study aimed to determine the population impact of patients with severe mental illness on violent crime. Method: Sweden possesses high-quality national registers for all hospital admissions and criminal convictions. All individuals discharged from the hospital with ICD diagnoses of schizophrenia and other psychoses (N=98,082) were linked to the crime register to determine the population-attributable risk of patients with severe mental illness to violent crime. The attributable risk was calculated by gender, three age bands (15–24, 25–39, and 40 years and over), and offense type. Results: Over a 13-year period, there were 45 violent crimes committed per 1,000 inhabitants. Of these, 2.4 were attributable to patients with severe mental illness. This corresponds to a population-attributable risk fraction of 5.2%. This attributable risk fraction was higher in women than men across all age bands. In women ages 25–39, it was 14.0%, and in women over 40, it was 19.0%. The attributable risk fractions were lowest in those ages 15–24 (2.3% for male patients and 2.9% for female patients). Conclusions: The population impact of patients with severe mental illness on violent crime, estimated by calculating the population-attributable risk, varies by gender and age. Overall, the population-attributable risk fraction of patients was 5%, suggesting that patients with severe mental illness commit one in 20 violent crimes.

Predicting the impact of in vitro fertilisation and other forms of assisted conception on perinatal and infant mortality in England and Wales: examining the role of multiplicity

The increased risk of perinatal and infant mortality observed among in vitro fertilisation (IVF) births and other assisted conception births is thought to be largely attributable to multiplicity. Using mortality statistics and estimates of the proportion of births following infertility treatment, we predicted the excess stillbirths and infant deaths associated with twins and higher order births resulting from assisted conception in England and Wales. According to our results, approximately 73 deaths could have been avoided in 2001 if all IVF infants had been born as singletons or as naturally occurring monozygotic twins, equating to a population attributable risk fraction of around 1% for perinatal and infant deaths. If we include all types of assisted conception, this figure was estimated to be around 4% of deaths-more than 220 perinatal and infant deaths in 2001. We confirm the public health importance of multiple births associated with assisted conception.

Driving-while-intoxicated history as a risk marker for general aviation pilots

The Federal Aviation Administration conducts background checking for driving-while-intoxicated (DWI) convictions on all pilots. This study examined the association between DWI history and crash risk in a cohort of 335,672 general aviation pilots. These pilots were followed up from 1994 to 2000 through the aviation crash surveillance system of the National Transportation Safety Board. At baseline, 3.4% of the pilots had a DWI history. DWI history was associated with a 43% increased risk of crash involvement (adjusted relative risk: 1.43; 95% confidence interval: 1.15–1.77). The population-attributable risk fraction for DWI history was estimated as 1.4%. In addition to DWI history, male gender, older age, and inexperience were associated with significantly increased risk of crash involvement. The results of this study support DWI history as a valid risk marker for general aviation pilots. The safety benefit of background checking for DWI history needs to be further evaluated.

Effects of physical activity and dietary calcium intake on bone mineral density and osteoporosis risk in a rural Thai population.

The objective of the study was to determine the effects of modifiable risk factors on bone mineral density in postmenopausal Thai women. Dietary calcium intake (g/day), energy expenditure (kcal/day), and sunlight exposure (h/day) were assessed in 129 rural Thai women aged 63 years (range 50 to 84 years). Bone mineral density (BMD) at the femoral neck, lumbar spine, and distal radius were measured by dual-energy X-ray absorptiometry (DXA). The average dietary calcium intake was 236 +/- 188 g/day (mean +/- SD), while the energy expenditure was 2,118 +/- 656 kcal/day with 1.1 +/- 1.7 h of sunlight exposure. In multiple linear regression analysis, dietary calcium intake, energy expenditure, and years since menopause were significant and independent predictors of BMD at various sites. The three factors together accounted for between 35% and 45% of the variance of BMD. The prevalence of osteoporosis (defined as BMD T-scores < or =-2.5) was 33% at the femoral neck, 42% at the lumbar spine, and 35% at the distal radius. The risk of osteoporosis was higher in women with lower dietary calcium intake (< or =138 mg/day; prevalence rate ratio [PRR], 1.4; 95% confidence interval [CI], 1.0 to 1.9), lower energy expenditure (< or =1,682 kcal; PRR, 1.7; 95% CI, 1.2 to 2.3), and greater years since menopause (> or =6 years; PRR, 2.6; 95% CI, 1.2 to 5.8). The population attributable risk fraction of osteoporosis risk due to the three factors was 70%. These results suggest that in the Thai population, low dietary calcium intake and low physical activity together with advancing years since menopause were independent risk factors for low BMD.

Social class differences in coronary heart disease in middle-aged British men: implications for prevention.

Though social class differences in coronary heart disease (CHD) are well recognized, few studies have assessed the effect of imprecision in social class assessment on the relationship or the overall contribution of social class to attributable CHD risk. Prospective observational study of the relationship between occupational social class (assessed at baseline and after 20 years), major CHD (coronary death and non-fatal myocardial infarction) and all-cause mortality rates over 20 years among 5628 middle-aged British men with no previous evidence of CHD. The age-adjusted hazard of major CHD for manual men relative to non-manual men was 1.41 (95% CI: 1.21, 1.64) before correction and 1.50 (95% CI: 1.25, 1.79) after correction for imprecision of social class measurement. The imprecision-corrected estimate was attenuated to 1.28 (95% CI: 1.06, 1.54) after adjustment for the adult coronary risk factors (blood cholesterol, blood pressure, body mass index, cigarette smoking, alcohol, physical activity, and lung function) and to 1.20 (95% CI: 0.99, 1.45) following further adjustment for height. The population attributable risk fraction of major CHD for social class (manual versus non-manual) was 22% after correction for imprecision in social class, which was reduced to 14% after adjustment for the adult coronary risk factors, and 10% after further adjustment for height. Similar results were obtained for all-cause mortality. Even taking account of measurement imprecision, the contribution of social class to overall CHD risk is modest. Population-wide strategies to reduce major CHD risk factors are likely to have greater potential benefits for CHD prevention than strategies designed specifically to reduce social inequalities in CHD.

Risk factors for norovirus, Sapporo-like virus, and group A rotavirus gastroenteritis.

Viral pathogens are the most common causes of gastroenteritis in the community. To identify modes of transmission and opportunities for prevention, a case-control study was conducted and risk factors for gastroenteritis attributable to norovirus (NV), Sapporo-like virus (SLV), and rotavirus were studied. For NV gastroenteritis, having a household member with gastroenteritis, contact with a person with gastroenteritis outside the household, and poor food-handling hygiene were associated with illness (population attributable risk fractions [PAR] of 17%, 56%, and 47%, respectively). For SLV gastroenteritis, contact with a person with gastroenteritis outside the household was associated with a higher risk (PAR 60%). For rotavirus gastroenteritis, contact with a person with gastroenteritis outside the household and food-handling hygiene were associated with a higher risk (PAR 86% and 46%, respectively). Transmission of these viral pathogens occurs primarily from person to person. However, for NV gastroenteritis, foodborne transmission seems to play an important role.

Re-assessing the contribution of serum total cholesterol, blood pressure and cigarette smoking to the aetiology of coronary heart disease: impact of regression dilution bias.

To estimate the combined contribution of serum total cholesterol, blood pressure and cigarette smoking to coronary heart disease (CHD) risk after adjustment for regression dilution bias. Six thousand, five hundred and thirteen middle-aged British men without CHD were followed for major CHD events over 10 years. The population attributable risk fraction (PARF) was predicted for a range of risk factor thresholds before and after adjustment for regression dilution of serum total cholesterol and blood pressure. Defining 'low-risk' individuals as being in the bottom tenth of the population distributions of serum total cholesterol (<5.2 mmol/l) and diastolic blood pressure (<70 mmHg) and a non-cigarette smoker, the PARF was 75%, increasing to 86% after adjustment for regression dilution. Regardless of the threshold criteria chosen, the PARF was substantially greater than 65% before adjustment for regression dilution and greater than 75% after adjustment. Exclusion of ex-smokers and passive smokers from the low-risk group increased estimates further. Adjustment for other coronary risk factors had little effect on the results. At least 80% of major CHD events in middle-aged men can be attributed to the three strongest risk factors. Population-wide control of these factors is crucial for effective CHD prevention.

Risk factors of perinatal mortality in Lithuania, 1997-1998.

The aim of this paper is to determine the risk factors of perinatal mortality in Lithuania during 1997-1998. The focus of the study is the 1997-1998 Medical Birth Register Database (N = 75,178) covering social-demographic factors, the obstetric anamnesis of previous pregnancies, as well as mothers health behaviour and pathology of the current pregnancy, delivery and obstetric aid. The multivariate analysis assessing odds ratios of risk factors for perinatal mortality using logistic regression has been carried out and related population attributable risk fractions were calculated. A statistically significant (p < 0.01) model predicting perinatal mortality has been obtained in which 19 out of 76 analysed factors have been distinguished to be statistically significant. The septic state of the mother during the delivery (OR = 13.3; CI = 8.9-19.9) and haemorrhage due to a premature placental separation (OR = 11.6; CI = 7.9-16.9) were associated with substantial increased risks of the foetus. Factors from other groups (perinatal pathology during previous pregnancies and social, behavioural or environmental factors) had somewhat lower, though significant, risk on perinatal mortality. The highest population attributable risk fraction (PARF) was found for the breech birth and foetal growth retardation (PARF = 13 percent and PARF = 9.7 percent, respectively). It should be pointed out that the impact of marital status on perinatal mortality was very high (PARF = 6.4 percent), even higher than that of some clinical factors, though its odds ratio was among the lowest (OR = 1.5; CI = 1.2-1.7). During 1997-1998, the highest risk for perinatal mortality in Lithuania was associated with obstetric aid during delivery and pathology of current pregnancy. These groups of risk factors had also the highest population attributable risk fraction.

Lamb and kid mortality in village flocks in the coastal savanna zone of Ghana.

A cohort study was designed to observe and follow up mortality in lambs and kids in 88 flocks of sheep and goats under the traditional production system in five villages within the coastal savanna zone of Ghana over a 2-year period. The overall mortality rates for kids and lambs were 30.8% and 33.5%, respectively. Significantly higher proportions of kids (80.2%) and lambs (75.6%) up to 3 months of age died compared to kids and lambs from 4 to 12 months of age. The differences in mortality rates, either between male and female kids and lambs or between single-born and multiple-birth kids and lambs, were not significant. The odds ratio (OR) and relative risks (RR) for lambs and kids, on the basis of sex and birth types, were not significant; neither were the values obtained for attributable risk, attributable fraction, population attributable risk and population attributable fraction. The overall mortality rate on the basis of species of animal was not significant. At the village level, significant differences in the proportions of mortality on the basis of sex were seen in two villages. At Akotokyir, more male lambs (54.2%) died compared to females (27.6%), while at Apewosika more female lambs (42.2%) died compared to males (16.7%). The only significant difference in mortality proportions on the basis of birth type at the village level was seen at Apewosika, where more single-born kids died (52.8%) compared to kids born with sibling(s) (28.4%). The significant ORs for mortalities were 3.10 for male lambs at Akotokyir, 3.35 for female lambs at Apewosika and 2.82 for single-born kids at Apewosika. The corresponding RRs were equally significant. On the basis of species, significantly more lambs died at Akotokyir (44.2%) and Kwesimprah (44.7%) compared to kids. The implications of these findings are discussed.

The impact of syphilis, HIV-1, and HIV-2 on pregnancy outcome in Bissau, Guinea-Bissau.

Syphilis remains a major cause of fetal loss and neonatal mortality in sub-Saharan Africa. Guinea-Bissau is the epicenter of the HIV-2 epidemic, and little is known about the impact of HIV-2 on pregnancy. To understand better the impact of maternal syphilis and HIV-2 on the outcomes of pregnancy in Bissau, Guinea-Bissau. Using a case-control design, maternal syphilis and HIV-2 seropositive results were examined in relation to adverse outcomes of pregnancy. From June 1997 to April 1998, women presenting to the Simao Mendes hospital of Bissau for a delivery or a spontaneous abortion were invited to participate in the study, and 1341 women were enrolled. The 743 control subjects were women who had delivered a term neonate with a birthweight greater than 2500 g that survived the first 28 days of life. The cases were classified into five groups of mothers according to the outcome of pregnancy: stillbirths (n = 185), spontaneous abortions (n = 89), premature deliveries (n = 256), small-for-gestation-age babies (n = 55), and neonatal deaths (n = 13). Among the control subjects, the prevalences of serologic syphilis and HIV infection were 3.9% and 7.9%, respectively. Positive syphilis serology results together with a rapid plasma reagin titer of 1:16 or more were associated with delivery of a stillborn (adjusted odds ratio [AOR], 6.05) and premature delivery (AOR, 2.98). In Bissau, the population-attributable risk fraction of syphilis was 7.2% (95% CI, 2.2-11.9%) for stillbirths and only 2.4% (95% CI, 0-5.8%) for premature deliveries. Spontaneous abortions, delivery of a small-for-gestation-age baby, and neonatal deaths were not associated with positive syphilis serology results. None of these pregnancy outcomes was significantly associated with HIV-2 infection. The effect of syphilis on the outcome of pregnancy in West Africa is similar to that reported from other parts of Africa. However, because the prevalence of positive syphilis serology results is relatively low, the impact of screening for syphilis on the outcome of pregnancy is likely to be relatively modest. The findings from this study confirm the absence of association between HIV-2 and an adverse pregnancy outcome.

Childhood abuse, household dysfunction, and the risk of attempted suicide throughout the life span: findings from the Adverse Childhood Experiences Study.

Suicide is a leading cause of death in the United States, but identifying persons at risk is difficult. Thus, the US surgeon general has made suicide prevention a national priority. An expanding body of research suggests that childhood trauma and adverse experiences can lead to a variety of negative health outcomes, including attempted suicide among adolescents and adults. To examine the relationship between the risk of suicide attempts and adverse childhood experiences and the number of such experiences (adverse childhood experiences [ACE] score). A retrospective cohort study of 17 337 adult health maintenance organization members (54% female; mean [SD] age, 57 [15.3] years) who attended a primary care clinic in San Diego, Calif, within a 3-year period (1995-1997) and completed a survey about childhood abuse and household dysfunction, suicide attempts (including age at first attempt), and multiple other health-related issues. Self-reported suicide attempts, compared by number of adverse childhood experiences, including emotional, physical, and sexual abuse; household substance abuse, mental illness, and incarceration; and parental domestic violence, separation, or divorce. The lifetime prevalence of having at least 1 suicide attempt was 3.8%. Adverse childhood experiences in any category increased the risk of attempted suicide 2- to 5-fold. The ACE score had a strong, graded relationship to attempted suicide during childhood/adolescence and adulthood (P<.001). Compared with persons with no such experiences (prevalence of attempted suicide, 1.1%), the adjusted odds ratio of ever attempting suicide among persons with 7 or more experiences (35.2%) was 31.1 (95% confidence interval, 20.6-47.1). Adjustment for illicit drug use, depressed affect, and self-reported alcoholism reduced the strength of the relationship between the ACE score and suicide attempts, suggesting partial mediation of the adverse childhood experience-suicide attempt relationship by these factors. The population-attributable risk fractions for 1 or more experiences were 67%, 64%, and 80% for lifetime, adult, and childhood/adolescent suicide attempts, respectively. A powerful graded relationship exists between adverse childhood experiences and risk of attempted suicide throughout the life span. Alcoholism, depressed affect, and illicit drug use, which are strongly associated with such experiences, appear to partially mediate this relationship. Because estimates of the attributable risk fraction caused by these experiences were large, prevention of these experiences and the treatment of persons affected by them may lead to progress in suicide prevention.

Breastfeeding, socio-economic conditions and nutritional status of children younger than 12 months in Brazil.

Taking account of socio-economic determinants such as maternal education and family income, nutritional status and its relationship to breastfeeding and socio-economic conditions were studied in 419 children aged 3-12 months in the city of Niterói in south-eastern Brazil. Data were obtained by sampling a population during a high coverage (90%) vaccination campaign in 1992. After stratifying by maternal educational level, the relative risk (prevalence ratio) for height-for-age (H/A) Z-score < -1 in relation to no breastfeeding was 2.2 (95% CI 1.1-4.2) for families where mothers had been educated for less than 4 years and 0.7 (95% CI 0.4-1.1) otherwise, indicating a significant interaction (modifying effect) between breastfeeding and the control variable (chi 2 = 7.4; p = 0.006). Similar results were found when family income was used as the stratification variable (RR 2.2, 95% CI 1.1-4.3 in the lower and RR 0.7, 95% CI 0.4-1.2 in the higher income stratum; chi 2 = 6.7; p = 0.009). The population-attributable risk fraction indicated that in the age group analysed a reduction of about 40% in the number of children with HAZ < -1 could be achieved in low-income/low-education families by the widespread adoption of breastfeeding.

Assessment of separate contributions to perinatal mortality of infertility history and treatment: a case-control analysis

Few studies have described the perinatal risks associated with infertility, other than for infertility treated by in-vitro fertilisation or gamete intrafallopian transfer. The aim of this analysis was to estimate the risks of perinatal death associated with treated and untreated infertility. A population-based case-control study of perinatal deaths was carried out in Leicestershire Health District over the period 1990-94, during which 60,922 babies were delivered. Of these, 567 perinatal deaths were associated with 542 women. 972 mothers were randomly selected as controls. Medical, obstetric, and social data were collected for cases and controls from the medical notes and interviews with the women. The relative risks of perinatal death associated with treated and untreated infertility before the index pregnancy were estimated as odds ratios by means of unconditional logistic regression analysis. 65 (10%) of cases and 34 (3.5%) of the controls had infertility before the index pregnancy. History of infertility in the index pregnancy, irrespective of treatment, increased the risk of perinatal death (odds ratio 2.9 [95% CI 1.8-4.5]). The population attributable risk fraction for perinatal death related to infertility was 6.2% (3.4-9.0). 45 (54%) of the deaths, even in the untreated group, were associated with immaturity. Compared with women without infertility, women with untreated infertility were at increased risk of perinatal death (3.3 [1.6-6.8]). The risk of perinatal death associated with multiple births did not explain this finding. Similarly, treated infertility also increased the risk of perinatal death (2.7 [1.5-4.7]); the risks associated with multiple births explained some, but not all, of this excess. In Leicestershire, the overall underlying risk of a mother experiencing at least one perinatal death over the study was 9.0 per 1000 women. For women who experience infertility, this risk increases by about 18 per 1000 (6-30). Counselling for women before any form of infertility treatment should include discussion of the risks of perinatal death. Our results would benefit from confirmation. However, we advocate that at antenatal booking a history of infertility, irrespective of treatment, should be sought, because these women have a significantly increased risk of perinatal death, particularly associated with prematurity.

Lifelong exposures and the potential for stroke prevention: the contribution of cigarette smoking, exercise, and body fat.

STUDY OBJECTIVE: To examine the potential for stroke prevention by avoidance of hazards related to lifestyle. Assessment of the lifelong contribution of both individual and combined exposures was a particular...