Biomedical subjects

M W Knuiman

Publications and source records attributed to M W Knuiman.

At least 19 recordsLinked to original sources

PubMed2006

Surgeon experience and trends in intraoperative complications in laparoscopic cholecystectomy.

BACKGROUND: Intraoperative complications, particularly bile duct injuries (BDIs), have increased since the introduction of laparoscopic cholecystectomy (LC). This excess risk is expected to decline as surgeon experience in laparoscopic surgery increases. METHODS: This was a population-based study of trends in intraoperative injuries in 33 309 cholecystectomies carried out in Western Australia between 1988 and 1998, based on hospital discharge abstracts. Endpoints were identified from diagnostic and procedure codes in index or postoperative readmissions, or a register of endoscopic retrograde cholangiopancreatography procedures, and validated using hospital records. Multivariate analysis was used to estimate the risk of complications associated with potential risk factors. RESULTS: Following the introduction of LC in 1991, the prevalence of all complications doubled by 1994 then stabilized, whereas that of BDI declined after 1994. The risk of complications increased with age, was higher in men, teaching and country hospitals, and was higher for LC and more complicated operations. It was lower when intraoperative cholangiography was performed and with increasing surgeon experience. Approximately 20 per cent of all complications and 30 per cent of BDIs were attributable to surgeons who had performed 200 or fewer cholecystectomies in the previous 5 years. CONCLUSION: The risk of intraoperative complications declined with increasing surgical experience and use of intraoperative cholangiography.

Bile Ducts↗

PubMed2006

The obesity-driven rising costs of type 2 diabetes in Australia: projections from the Fremantle Diabetes Study.

BACKGROUND: The cost of diabetes is high for both the individual and society. Future health-care planning requires patient-level diabetes-attributable health-care cost data that have not previously been available for Australia. AIM: To determine Australian national direct diabetes-attributable health-care costs for known type 2 diabetes in 2000 and project these to 2051. METHODS: A total of 1294 patients with type 2 diabetes was recruited to the Fremantle Diabetes Study between 1993 and 1996. A bottom-up, prevalence-based approach using diabetes-attributable costs provided average annual per patient health-care costs (in year 2000 A$). Costs were extrapolated to 2051 using Australian type 2 diabetes prevalence figures and Australian Bureau of Statistics population projections, assuming that prevalence rates (i) remain at current levels and (ii) rise steadily. RESULTS: Total annual direct diabetes-attributable health-care costs in 2000 in Australia for people > or =25 years with known type 2 diabetes were estimated at A$636 million. As a result of ageing, the number of people with type 2 diabetes will double between 2000 and 2051 with a 2.5-fold increase in diabetes-attributable health-care costs. If obesity and inactivity prevalence rates continue to rise, prevalence rates of type 2 diabetes will further increase. The number of people with type 2 diabetes in 2051 may be 3.5 times higher than in 2000 with a 3.7-fold cost increase. CONCLUSIONS: The financial burden of treating type 2 diabetes could quadruple by 2051 unless more is done to prevent type 2 diabetes and its complications. A smaller proportion of the population will have the capacity to fund these rising health-care costs.

Adult↗

PubMed2004

Risk of death in prisoners after release from jail.

OBJECTIVE: To compare the risk of death in a cohort of Western Australian released prisoners with the risk experienced by the general population of Western Australia. METHODS: A cohort study of prisoners in Western Australia whose last date of release ranged from 1 January 1994 to 1 January 1999. Overall mortality and cause of death were determined by data linkage to the Registrar General's record of deaths. RESULTS: Aboriginal prisoners had a significantly lower survival rate after release than non-Aboriginal prisoners (p < 0.0001). When compared with their peers in the Western Australian community, both Aboriginal and non-Aboriginal prisoners were found to have an increased relative risk of death. Female non-Aboriginal released prisoners aged between 20 and 40 years were 17.8 (95% CI 8.1-27.5) times more likely to die than other female non-Aboriginals in Western Australia in the same age range. Male non-Aboriginal prisoners aged 20-40 years were 6.3 (95% CI 5.2-7.4) times more likely to die than their counterparts in the WA community. Female Aboriginal released prisoners were 3.4 (95% CI 1.2-5.6) times more likely to die than their peers, while male Aboriginal released prisoners were 2.9 (95% CI 2.2-3.5) times more likely to die. In their first six months after release, female non-Aboriginal prisoners aged 20 to 40 years were 69.1 (95% CI 17.9-120.3) times more likely to die than their counterparts in the WA community. The main causes of excess death were related to drug and alcohol abuse. CONCLUSION: All prisoners were at greater than expected relative risk of death after release from prison, with female non-Aboriginal prisoners at particularly high relative risk.

Adult↗

PubMed2004

Trends in coronary artery revascularisation procedures in Western Australia, 1980-2001.

OBJECTIVES: To describe trends in the use of coronary artery revascularisation procedures (CARPs) and to determine whether or when CARP rates will stabilise. SETTING: State of Western Australia. PATIENTS: All patients treated by coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) between 1980 and 2001. DESIGN: Descriptive study. MAIN OUTCOME MEASURES: Age standardised rates of first and total CARPs, CABGs, and PCIs. RESULTS: Overall rates for both total and first CARPs among men and women rose steeply from 1980 to 1993, when they abruptly stabilised or actually started to decline. Rates in age groups under 65 years tended to rise earlier in the period and remained relatively flat, while rates for people over the age of 75 years started to rise later and were still increasing at the end of the study. CONCLUSIONS: Despite continuing increases in capacity to perform both CABG and PCI in Western Australia and evidence of continuing increases in the use of CARPs in the elderly population, rates appear to have stabilised for the first time since they were introduced.

Adult↗

PubMed2004

Trends in two year risk of repeat revascularisation or death from cardiovascular disease after coronary artery bypass grafting or percutaneous coronary intervention in Western Australia, 1980-2001.

AIMS: To investigate whether, over the 21 year period 1980-2001, there had been a reduction in the risk of repeat revascularisation or death from cardiovascular disease in the cohort of all patients who were treated by coronary revascularisation in Western Australia. SETTING: State of Western Australia. PATIENTS: All patients treated by coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) between 1980 and 2001. DESIGN: Cohort study. MAIN OUTCOME MEASURES: Risk of repeat coronary artery revascularisation procedures (CARP) and risk of death from cardiovascular disease after first CARP. RESULTS: After a CABG procedure, the two year risk of repeat revascularisation remained low (less than 2%) across the period 1980-2001. For PCI, however, this risk declined significantly from 33.6% in 1985-9 to 12.4% in 2000-1. The risk of death from cardiovascular disease after a CARP declined by about 50% between 1985 and 2001. CONCLUSIONS: Outcomes such as the risk of repeat revascularisation and the risk of death from cardiovascular disease have improved significantly for patients who underwent CARPs across the period 1980-2001. This has occurred despite an increasing trend in first CARP rates among older people and those with a recent history of myocardial infarction.

Adult↗

PubMed2003

Serum ferritin and cardiovascular disease: a 17-year follow-up study in Busselton, Western Australia.

The association between serum ferritin level and coronary heart disease (CHD) and stroke events was evaluated in a long-term Western Australia prospective study in 1981-1998. The cohort consisted of the 1612 men and women aged 40-89 years who participated in the 1981 Busselton Health Survey and who were free of cardiovascular disease at that time. Serum ferritin levels were obtained from serum samples stored frozen since 1981. The outcomes of interest were time to first CHD event (hospital admission or death) and time to first stroke event. Case-cohort sampling was used to reduce costs and preserve serum but still allow efficient analysis. Ferritin assays were performed for 217 CHD cases, 118 stroke cases, and a random sample of 450 of the total cohort. Proportional hazards regression models were used to obtain age-adjusted and multivariate-adjusted hazard ratios for ferritin level in relation to CHD and stroke. The hazard ratio for the highest tertile group compared with the lowest group was 0.96 (95% confidence interval: 0.60, 1.53) for CHD and 1.43 (95% confidence interval: 0.78, 2.64) for stroke. Little or no evidence was found that ferritin level was a risk factor for cardiovascular disease.

Adult↗

PubMed2003

Health status of users of hormone replacement therapy by hysterectomy status in Western Australia.

STUDY OBJECTIVES: To compare the demographic, behavioural, and biological correlates of use of hormone replacement therapy (HRT) in women with an intact uterus and women who have undergone hysterectomy. DESIGN: Cross sectional analysis of data from the Busselton Health Study and the 1994 Healthway-National Heart Foundation Risk Factor Survey. SETTING: Busselton and Perth, Western Australia, 1994. PARTICIPANTS: 2540 women aged 35-79 years. MAIN OUTCOME MEASURES: Demographic, behavioural, and biological correlates of use of HRT by hysterectomy status. RESULTS: In women with an intact uterus, after adjustment for age and place of residence, current use of HRT was significantly associated with having a professional level of occupation, ever use of alcohol, having a history of smoking, and a lower body mass index. Current users of HRT had significantly lower levels of total cholesterol and higher levels of triglycerides than non-users. In women who had undergone hysterectomy, the only non-biological characteristic associated with use of HRT was having a history of smoking. Current users of HRT had lower levels of systolic blood pressure, lower levels of LDL cholesterol, higher levels of HDL cholesterol, and higher levels of triglycerides. The association between use of HRT and participation in exercise, level of systolic blood pressure, level of HDL cholesterol, and total/HDL cholesterol ratio varied significantly by hysterectomy status. After adjustment for age and place of residence, the mean levels of systolic and diastolic blood pressure, body mass index, waist/hip ratio, LDL cholesterol, and total/HDL cholesterol ratio were highest in women who had undergone hysterectomy and were not using HRT. CONCLUSIONS: Demographic/behavioural and biological correlates of use of HRT varied depending on hysterectomy status. Demographic and behavioural characteristics were more important as selection factors for use of HRT in women with an intact uterus than in women who had undergone hysterectomy. Women who had undergone hysterectomy and were not using HRT had a significantly worse profile for CHD than did women with an intact uterus. These results indicate that any bias in estimates of the protective effect of HRT on risk of CHD in observational studies is likely to depend on the prevalence of hysterectomy within the study population. Hysterectomy status needs to be taken into account in any studies that investigate the effect of HRT on risk of CHD.

Adult↗

PubMed2002

Trends in road injury hospitalisation rates for Aboriginal and non-Aboriginal people in Western Australia, 1971-97.

OBJECTIVE: To examine trends in road injury hospitalisation rates for Aboriginal and non-Aboriginal people in Western Australia. METHODS: Data from the Western Australian Hospital Morbidity Data System for the years between 1971 and 1997 were analysed. Poisson regression models were fitted to determine whether the trends were significant. RESULTS: The rate of hospitalisation due to road injury for Aboriginal people (719.1 per 100 000 population per year) over the time period examined was almost twice as high as that for non-Aboriginal people (363.4 per 100 000 population per year). Overall, the results showed that while hospitalisations from road injury involving non-Aboriginal people have been decreasing by 6.7% per three year period since 1971, the rates of hospitalisation for Aboriginal people have been increasing by 2.6% per three year period. Both of these trends were statistically significant. The alarming increasing trend observed for Aboriginal people was more pronounced in males, those aged 0-14 years and over 45 years, and for those living in rural areas. CONCLUSIONS: As the rates of road injury for Aboriginal people are higher than for non-Aboriginal people, and are also following an increasing trend, road safety issues involving Aboriginal people need to be addressed urgently by health and transport authorities.

Accidents, Traffic↗

PubMed2001

Association of hemostatic variables with MRI-detected cerebral abnormalities: the atherosclerosis risk in communities study.

OBJECTIVES: Population-based and clinical prospective studies have shown independent associations of several hemostatic factors with ischemic heart disease and stroke. MRI-detected cerebral infarcts and white matter lesions are often detected in elderly individuals without clinical disease. It has been hypothesized that these types of lesions are often the consequence of cerebral ischemic damage and may be the precursors of clinical stroke. METHODS: This study examined the relation between a range of hemostatic factors measured at baseline in middle-aged participants who were free of diagnosed cardiovascular disease in the Atherosclerosis Risk in Communities Study and MRI-detected cerebral abnormalities at a 6-year follow-up examination. RESULTS: Plasma fibrinogen and perhaps von Willebrand factor were associated positively, and protein C was associated negatively, with cerebral infarctions. Adjusted for other risk factors, the odds ratio for cerebral infarction was 1.21 (95% confidence interval, CI = 1.02-1.44) per standard deviation increment for fibrinogen, 1.15 (95% CI = 0.97-1.37) per standard deviation increment for von Willebrand factor, and 0.77 (95% CI = 0.62-0.95) per standard deviation increment for protein C. No hemostatic factor, however, was associated with white matter disease. CONCLUSIONS: This study has only a follow-up MRI, and it is likely that some MRI lesions were present at baseline. Nevertheless, increased levels of fibrinogen and von Willebrand factor and reduced levels of protein C appear to be associated with cerebral infarction identified by MRI.

Aged↗

PubMed2001

Familial aggregation and heritability of adult lung function: results from the Busselton Health Study.

Decreased spirometric indices are characteristic of asthma and other respiratory diseases. The aim of this study was to investigate the genetic and environmental components of variance of forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) measured in adulthood in an Australian population-based sample of 468 Caucasian nuclear families. The inter-relationships of the genetic determinants of these traits with asthma and atopic rhinitis were also investigated. Serial cross-sectional studies were conducted in the town of Busselton in Western Australia between 1966 and 1981 and follow-up of previous attendees was undertaken in 1995. Data from each subject included in this study were from a single survey in adulthood (25-60 yrs of age) when the subject was as close to age 45 yrs as possible. Multivariate analysis suggested that FEV1 and FVC levels were associated with age, sex, height, tobacco smoke exposure, asthma and atopic rhinitis. After adjustment for relevant covariates, FEV1 levels had a narrow-sense heritability (h2N) of 38.9% (SE 9.1%). FVC levels had an h2N of 40.6% (SE 8.9%). Extended modelling demonstrated little overlap in the genetic determinants of asthma or atopic rhinitis and either FEV1 or FVC levels. The results of this study were consistent with the existence of important genetic determinants of adult lung function that are independent of asthma or other atopic disease, cigarette smoking, height, age or sex.

Adult↗

PubMed2000

Use of conditional and marginal odds-ratios for analysing familial aggregation of binary data.

We propose a method for measuring familial aggregation of binary outcomes that incorporates unconditional, i.e., marginal, odds-ratios, for measuring association between outcomes within generations while using conditional odds-ratios to measure association between generations. This method may be used together with marginal odds-ratio models to explore the strength of association between individuals within a generation while accounting for the outcomes of predecessors. Interpretation of resulting odds-ratios is straightforward and a number of features of the method are discussed. An example, using smoking status data from Busselton Health Study families, is used to illustrate our approach.

Bias↗

PubMed2000

Road safety issues in remote Aboriginal communities in Western Australia.

A series of interviews with the chairpersons of Aboriginal communities in a remote area of Western Australia were conducted to examine their attitudes to road safety problems. It was found that some road safety issues that were expected to be considered problems were not necessarily seen to be so by those interviewed. This finding suggests that the first stage of a road safety intervention program for Aboriginal people may need to include an awareness raising component. It also suggests that there is a need for more detailed research defining particular problems more accurately before effective and culturally appropriate countermeasures are developed.

Accidents, Traffic↗

PubMed2000

Body mass index and alternative indices of obesity in relation to height, triceps skinfold and subsequent mortality: the Busselton health study.

OBJECTIVES: The ideal index for leanness and obesity in epidemiological studies should correlate strongly with body weight and with a direct measure of fat while minimizing the influence of height. The preferred index is expected to show meaningful associations with subsequent mortality. Our aims were to compare weight/height, weight/height(2) (body mass index or BMI), and weight/height(3) as candidates for this index. DESIGN: We analysed cross-sectional data from surveys of 6948 adults (3334 men (mean age 43 y, mean BMI 24.8 kg/m2), and 3614 women (mean age 42 y, mean BMI 24.3 kg/m2)) in Busselton, Australia whose weight, height, triceps skinfold, and cardiovascular risk factors were measured from 1966 through to 1978. In these same subjects we studied the mortality risks of indices of obesity using Cox regression analysis for survival time from first survey to death, or to follow up at the end of December 1995, after adjustment for age. Subjects dying within 5 y of the baseline survey were excluded from the analysis to avoid the bias of concurrent illness. We also studied subgroups including never smokers, subjects with no heart disease, and subjects <60 years of age at first survey. RESULTS: In men, weight/height2 met the criteria for a satisfactory index in that there was a very strong correlation with triceps skinfold, and a negligible correlation with height. For women, weight/height was as good a measure as weight/height2, with both having strong correlations with triceps skinfold, and minimal correlations with height. Weight/height2 as a predictor of mortality in men of all ages showed the typical U-shaped associations that were similar and consistent and of variable statistical significance. The significances of the hazard ratio curves were the strongest for cardiovascular disease deaths (all men P=0.001; men without heart disease at baseline P<0.001; never smoking men P=0.007). In never smoking men there was a near linear positive relationship with all-cause mortality (P=0.018). In women weight/height2 showed no consistent associations with mortality. There was a shallow U-shaped relationship with all-cause mortality (P=0.087), also seen in never smoking women (P=0.075). In assessing 'ideal' weight for height in this population, a weight/height2 of 25 kg/m2 (range 22.5-27.5 kg/m2) is appropriate. Weight/height and mortality showed very similar patterns in men to weight/height2 with quite similar levels of statistical significance. In women much more pronounced U-shaped curves were apparent in all groups and subgroups, with a significant all-cause mortality trend for all women (P=0.029) and never smoking women (P=0.034). In assessing 'ideal' weight for height a weight/height of 42.5 kg/m (range 35-50 kg/m) appears appropriate for men and women. CONCLUSIONS: Weight/height2 is an appropriate index of leanness and obesity in males at all ages, whereas weight/height is at least as good an index for females. In mortality studies weight/height2 and weight/height predict mortality similarly in males, but weight/height is a better discriminant of mortality in females. International Journal of Obesity (2000)24, 108-115

Adult↗

PubMed1999

Lung function, respiratory symptoms, and mortality: results from the Busselton Health Study.

PURPOSE: This study examines the association between lung function [percentage predicted FEV, (forced expiratory volume in 1 s)] and respiratory symptoms (asthma, bronchitis, wheeze, dyspnea) and mortality from all causes; coronary heart disease, stroke, cancer, and respiratory disease in a cohort of 2,100 men and 2,177 women in the Busselton Health Study followed for 20-26 years for mortality. METHODS: A total of 840 men and 637 women died during the follow-up period, and Cox proportional hazards regression was used to assess the relationships between risk factors and mortality. RESULTS: Lung function was significantly and independently predictive of mortality from all causes, coronary heart disease, cancer, and respiratory disease in both men and women, and of mortality from stroke in women. There was evidence that, among men, the association was stronger in current and former smokers as compared to those who never smoked. After adjustment for age, smoking, lung function, coronary heart disease, blood pressure, treatment for hypertension, total cholesterol, body mass index, and alcohol consumption, dyspnea was significantly related to total mortality in men and women and to respiratory disease mortality in men, and asthma was significantly related to respiratory disease mortality in women. CONCLUSIONS: Lung function is associated with mortality from many diseases independent of smoking and respiratory symptoms. Although most respiratory symptoms are associated with smoking and lung function, after controlling for smoking and lung function, only dyspnea is associated with mortality from nonrespiratory causes.

Adult↗

PubMed1999

Associations between white blood cell count, lung function, respiratory illness and mortality: the Busselton Health Study.

An independent association between reduced levels of lung function and increased mortality from nonrespiratory causes has been observed in a number of studies. Since the total white blood cell count (WBC) has been related to both death from coronary heart disease and to levels of lung function, the relationship between these parameters was examined in subjects from the Busselton Health Surveys. Questionnaires regarding respiratory and cardiac illness and smoking habits were administered and total WBC, forced expiratory volume in one second (FEV1) and forced vital capacity measured in 2,105 males and 2,186 females at their initial attendance at a Busselton Health Survey in 1969, 1972 or 1975. Mortality follow-up to 1995 was completed. Multiple linear regression showed that smoking, increasing age, reduced FEV1 (% predicted) and a history of bronchitis were associated with increased WBC. Reduction of FEV1 (% pred) by 20%, a history of dyspnoea and an increase in WBC of 1,300 cells x mL(-1) were predictive of increased mortality from all causes or coronary heart disease by approximately 20, 100 and 10% respectively, independent of smoking. Removing WBC from the regression model did not significantly change the relationship between FEV1 and mortality. The study shows that the white blood cell count, forced expiratory volume in one second and dyspnoea are independently related to mortality in both males and females and that the effect of forced expiratory volume in one second on mortality is not explained by the white blood cell count.

Adult↗

PubMed1999

Complications of cholecystectomy: risks of the laparoscopic approach and protective effects of operative cholangiography: a population-based study.

BACKGROUND: Previous studies suggest that laparoscopic cholecystectomy (LC) is associated with an increased risk of intraoperative injury involving the bile ducts, bowel, and vascular structures compared with open cholecystectomy (OC). Population-based studies are required to estimate the magnitude of the increased risk, to determine whether this is changing over time, and to identify ways by which this might be reduced. METHODS: Suspected cases of intraoperative injury associated with cholecystectomy in Western Australia in the period 1988 to 1994 were identified from routinely collected hospital statistical records and lists of persons undergoing postoperative endoscopic retrograde cholangiopancreatography. The case records of suspect cases were reviewed to confirm the nature and site of injury. Ordinal logistic regression was used to estimate the risk of injury associated with LC compared with OC after adjusting for confounding factors. RESULTS: After the introduction of LC in 1991, the proportion of all cholecystectomy cases with intraoperative injury increased from 0.67% in 1988-90 to 1.33% in 1993-94. Similar relative increases were observed in bile duct injuries, major bile leaks, and other injuries to bowel or vascular structures. Increases in intraoperative injury were observed in both LC and OC. After adjustment for age, gender, hospital type, severity of disease, intraoperative cholangiography, and calendar period, the odds ratio for intraoperative injury in LC compared with OC was 1.79. Operative cholangiography significantly reduced the risk of injury. CONCLUSION: Operative cholangiography has a protective effect for complications of cholecystectomy. Compared with OC, LC carries a nearly twofold higher risk of major bile, vascular, and bowel complications. Further study is required to determine the extent to which potentially preventable factors contribute to this risk.

Aged↗

PubMed1999

Decline in lung function and mortality: the Busselton Health Study.

BACKGROUND: There is a direct association between level of lung function, measured by forced expiratory volume in 1 second (FEV1) and mortality rates. A low FEV may result from an increased decline in FEV1 with age, which may be an independent predictor of mortality. OBJECTIVE: To examine the association between decline in FEV1 and mortality in a cohort from a community health study. SETTING AND METHODS: From five cross sectional studies in Busselton between 1969 and 1981 a cohort of 751 men and 940 women was identified who had three assessments of lung function over a six year period and had other health related data collected. Each subject's average FEV1 and decline in FEV1 (litre/year) were calculated from these three measurements. Mortality follow up to December 1995 was obtained. Cause of death was taken as the certified cause of death from the death certificate using ICD9 categories. RESULTS: The average decline in FEV1 was 0.04 litre per year (SD = 0.07) for men and 0.03 litre per year (SD = 0.06) for women. Average FEV1 was significantly associated with all cause and cardiovascular disease mortality in both sexes. In women there was a significant association between decline in FEV1 and death from all causes, after adjusting for average FEV1, age, smoking, coronary heart disease, and cardiovascular disease risk factors; a 0.05 litre per year increase in the rate of decline of FEV1 increased the risk of death for all causes by 1.23 (95% confidence interval 1.06, 1.44). In men the effect of decline in FEV1 on death rate was less; for all men the hazard ratio for a 0.05 litre/year greater decline in FEV1 was 1.19 (0.99, 1.21). CONCLUSION: Decline in lung function, measured by FEV1 is a predictor of death, independent of average FEV1 and risk factors for cardiovascular disease.

Alcohol Drinking↗

PubMed1999

Effect of dichotomising a continuous variable on the assessment of familial aggregation: an empirical study using body mass index data from the Busselton Health Study.

BACKGROUND: Continuous measures are often dichotomised according to some meaningful threshold. When measures of association are the study focus, such as in familial aggregation studies, we may use an odds-ratio (OR), instead of a Pearson correlation coefficient, to measure correlation between outcomes. In this paper, we examine the effect of using different threshold values on the resulting OR estimates and their statistical efficiency. METHODS: We use an example based on obesity data, in the form of BMI measurements on family members, to guide a study of the OR based on four-fold probabilities which result when a pair of normally distributed outcomes is dichotomised at a certain value. This leads to a study of outcomes from simulated nuclear family data. As a possible alternative, we also assess the performance use of a simple tetrachoric correlation coefficient, the dichotomous analogue of Pearson's correlation coefficient. RESULTS: The studies indicate that dichotomisation at values close to the mean leads to results more comparable to the continuous equivalent. The results show that, in our setting, there is a positive relationship between threshold value and resulting OR, and between threshold value and resulting standard errors. The value of the tetrachoric correlation coefficient decreases, relative to Pearson's correlation coefficient, as threshold values deviate from the mean. DISCUSSION: Familial OR that result from dichotomisation are influenced by the choice of threshold value. We discuss implications of this and related issues on the interpretation of results.

Adult↗