Search

To investigate the time-dependent effects of traditional risk factors on functional disability in all-cause mortality post-stroke, we evaluated data from a long-term stroke cohort. Baseline cerebrovascular risk factors (CVRF) and functionality at 1 and 6 months were evaluated in survivors from a prospective stroke cohort using the modified Rankin scale (m-RS), which classifies participants as improvement of disability, unchanged disability (at least moderate), and worsening disability. Cox regression models considering baseline risk factors, medication use, and functionality 6 months after stroke were fitted to identify their time-dependent effects up to 12 years of follow-up. Adjusted hazard ratios (HR) with 95% confidence intervals (CI) are presented. Among 632 survivors (median age 68, 54% male, 71% first-ever episode), age and functional disability (unchanged and worsening) 6 months after ischemic stroke had time-dependent effects on all-cause mortality risk up to 12 years of follow-up. The most impacting risk factors were unchanged (at least moderate) (HR, 2.99; 95%CI: 1.98-4.52) and worsening disability (HR, 2.85; 95%CI: 1.26-6.44), particularly in the first two years after a stroke event (Time 1: ≥6 mo to <2.5 y). Worsening disability also impacted mortality in the period from ≥2.5 to <7.5 years (Time 2) of follow-up (HR, 2.43 (95%CI: 1.03-5.73). Other baseline factors had a fixed high-risk effect on mortality during follow-up. Post-stroke and continuous medication use had a fixed protective effect on mortality. Functional disability was the main contributor with differential risks of mortality up to 12 years of follow-up.

The longitudinal association between psoriasis and carotid intima-media thickness (CIMT) has not yet been established. This study aimed do compare CIMT and its change (∆CIMT) after an 8-year follow-up according to psoriasis diagnosis and the association with risk factors in the ELSA-Brasil study. Data from 7564 participants were analyzed (median age of 50.0 [44.0-57.0] years, 56.9% women). CIMT was assessed by ultrasound and ∆CIMT was calculated by subtracting baseline values from follow-up values. Psoriasis participants were identified by self-reported medical diagnosis (n=143) and compared with matched participants without disease (n=572) and with the entire sample without psoriasis (n=7421). Baseline CIMT explained the 8-year CIMT increase only in 36.9% among psoriasis participants and in ∼43.0% in participants without disease. CIMT was associated with age (β=0.002, P=0.002) and hypertension (β=0.029, P=0.034) in psoriasis participants. Among participants without psoriasis, CIMT was associated with age, male sex, low educational attainment, past smoking, obesity, diabetes, hypertension, and dyslipidemia (P<0.05). There was an inverse association of CIMT with private health insurance (β=-0.004, P=0.042) and White ethnicity (β=-0.006, P=0.004) in the entire sample without psoriasis but not in matched participants. Psoriasis participants showed an inverse association between ∆CIMT and diabetes (β=-0.214, P=0.011), while the entire sample without psoriasis showed an inverse association between ∆CIMT and age (β=-0.005, P<0.001), past smoking (β=-0.048, P=0.009), and hypertension (β=-0.048, P=0.009). In conclusion, psoriasis was not associated with CIMT after an 8-year follow-up. The inverse association of ∆CIMT with diabetes in psoriasis participants needs further clarification.

Current data shows that the autonomic and vascular systems can influence each other. However, only a few studies have addressed this association in the general population. We aimed to investigate whether heart rate variability (HRV) was associated with coronary artery calcium (CAC) in a cross-sectional analysis of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). We examined baseline data from 3138 participants (aged 35 to 74 years) without previous cardiovascular disease who underwent CAC score assessment and had validated HRV recordings. Prevalent CAC was defined as a CAC score>0, and HRV analyses were performed over 5-min segments. We detected CAC score>0 in 765 (24.4%) participants. Subgroup analyses in older participants (≥49 years) adjusted for sociodemographic and clinical variables revealed that CAC score>0 was associated with lower values of standard deviation of NN intervals (SDNN) (odds ratio [OR]=1.32; 95%CI: 1.05,1.65), root mean square of successive differences between adjacent NN intervals (RMSSD) (OR=1.28; 95%CI: 1.02,1.61), and low frequency (LF) (OR=1.53, 95%CI: 1.21,1.92). Interaction analysis between HRV indices and sex in age-stratified groups revealed significant effect modification: women showed increased OR for prevalent CAC in the younger group, while for men, the associations were in the older group. In conclusion, participants aged ≥49 years with low SDNN, RMSSD, and LF values were more likely to present prevalent CAC, suggesting a complex interaction between these markers in the pathogenesis of atherosclerosis. Furthermore, our results suggested that the relationship between CAC and HRV might be sex- and age-related.

The systematic assessment of cognitive performance of older people without cognitive complaints is controversial and unfeasible. Identifying individuals at higher risk of cognitive impairment could optimize resource allocation. We aimed to develop and test machine learning models to predict cognitive impairment using variables obtainable in primary care settings. In this cross-sectional study, we included 8,291 participants of the baseline assessment of the ELSA-Brasil study, who were aged between 50 and 74 years and were free of dementia. Cognitive performance was assessed with a neuropsychological battery and cognitive impairment was defined as global cognitive z-score below 2 standard deviations. Variables used as input to the prediction models included demographics, social determinants, clinical conditions, family history, lifestyle, and laboratory tests. We developed machine learning models using logistic regression, neural networks, and gradient boosted trees. Participants' mean age was 58.3±6.2 years, 55% were female. Cognitive impairment was present in 328 individuals (4%). Machine learning algorithms presented fair to good discrimination (areas under the ROC curve between 0.801 and 0.873). Extreme Gradient Boosting presented the highest discrimination, high specificity (97%), and negative predictive value (97%). Seventy-six percent of the individuals with cognitive impairment were included among the highest ranked individuals by this algorithm. In conclusion, we developed and tested a machine learning model to predict cognitive impairment based on primary care data that presented good discrimination and high specificity. These characteristics could support the detection of patients who would not benefit from cognitive assessment, facilitating the allocation of human and economic resources.

Sarcopenia and sleep problems share common physiopathology. We aimed to investigate the association of sleep disturbances with sarcopenia and its defining components in Brazilian middle-aged and older adults. In this cross-sectional analysis of the second wave of the ELSA-Brasil study, we included data from 7948 participants aged 50 years and older. Muscle mass was evaluated by bioelectrical impedance analysis and muscle strength by hand-grip strength. Sarcopenia was defined according to the Foundation for the National Institutes of Health criteria. Sleep duration and insomnia complaint were self-reported. Short sleep duration was considered as ≤6 h/night and long sleep duration as >8 h/night. High risk of obstructive sleep apnea (OSA) was assessed using the STOP-Bang questionnaire. Possible confounders included socio-demographic characteristics, lifestyle, clinical comorbidities, and use of sedatives and hypnotics. The frequencies of sarcopenia, low muscle mass, and low muscle strength were 1.6, 21.1, and 4.1%, respectively. After adjustment for possible confounders, high risk of OSA was associated with low muscle mass (OR=2.17, 95%CI: 1.92-2.45). Among obese participants, high risk of OSA was associated with low muscle strength (OR=1.68, 95%CI: 1.07-2.64). However, neither short nor long sleep duration or frequent insomnia complaint were associated with sarcopenia or its defining components. In conclusion, high risk of OSA was associated with low muscle mass in the whole sample and with low muscle strength among obese participants. Future studies are needed to clarify the temporal relationship between both conditions.

Recent evidence suggests that glaucoma and Alzheimer's disease are neurodegenerative diseases sharing common pathophysiological and etiological features, although findings are inconclusive. We sought to investigate whether self-reported glaucoma patients without dementia present poorer cognitive performance, an issue that has been less investigated. We employed cross-sectional data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) and included participants ≥50 years of age without a known diagnosis of dementia and a self-reported glaucoma diagnosis. We excluded those with previous stroke, other eye conditions, and using drugs that could impair cognition. We evaluated cognition using delayed word recall, phonemic verbal fluency, and trail making (version B) tests. We used multinomial linear regression models to investigate associations between self-reported glaucoma with cognition, adjusted by several sociodemographic and clinical variables. Out of 4,331 participants, 139 reported glaucoma. Fully-adjusted models showed that self-reported glaucoma patients presented poorer performance in the verbal fluency test (β=-0.39, 95%CI=-0.64 to -0.14, P=0.002), but not in the other cognitive assessments. Thus, our results support the hypothesis that self-reported glaucoma is associated with poor cognitive performance; however, longitudinal data are necessary to corroborate our findings.

Previous analyses of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) identified four main dietary patterns (DP). The aim of this study was to explore the association between the previously defined DP and renal function (RF). A cross-sectional study using the ELSA-Brasil baseline data was carried out. DP ("traditional", "fruits and vegetables", "bakery", and "low sugar/low fat), metabolic syndrome (MS) using the Joint Interim Statement criteria, microalbuminuria (MA), and glomerular filtration rate (eGFR) through the CKD-EPI equation were evaluated. Abnormal RF was defined as eGFR<60 mL·min-1·(1.73 m2)-1 and MA≥3.0 mg/dL. Factors associated with RF were determined and mediation analysis was performed to investigate the association between DP, MS, and RF. A total of 15,105 participants were recruited, with a mean age of 52±9 years; 8,134 participants (54%) were females. The mediation analysis identified indirect associations between "bakery" and "fruits and vegetables", and both were associated with decreased eGFR and albuminuria in both genders, compared with "traditional" and "low sugar/low fat" patterns in the general population. There was a direct association of the "bakery" pattern with MA in men (OR: 1.17, 95%CI: 1.92-1.48). The "fruits and vegetables" pattern also showed a direct association with reduced eGFR in women (OR: 1.65, 95%CI: 1.28-2.12), although there was no significance after adjustment. The "fruits and vegetables" and "bakery" DPs were associated with renal dysfunction. The only independent, direct association was between "bakery" DP and MA in men, raising concerns about DP and renal damage in men.

Body fat distribution predicts cardiovascular events better than body-mass index (BMI). Waist circumference (WC) and neck circumference (NC) are inexpensive anthropometric measurements. We aimed to present the conditional distribution of WC and NC values according to BMI, stratified by age and sex, from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) baseline data. We analyzed 15,085 ELSA-Brasil participants with complete data. We used spline quantile regression models, stratified by sex and age, to estimate the NC and WC quantiles according to BMI. To test a putative association between age and median NC or WC values, we built sex-specific median regression models using both BMI and age as explanatory variables. We present estimated 25th, 50th, 75th, and 90th percentiles for NC and WC values, according to BMI, age, and sex. Predicted interquartile intervals for NC values varied from 1.6 to 3.8 cm and, for WC values, from 5.1 to 10.3 cm. Median NC was not associated with age in men (P=0.11) nor in women (P=0.79). However, median WC increased with advancing age in both sexes (P<0.001 for both). There was significant dispersion in WC and NC values for a given BMI and age strata for both men and women. WC, but not NC values, were associated with increasing age. The smaller influence of advancing age on the relationship between BMI and NC (compared to WC) values may be useful in longitudinal studies.

Carotid artery assessment by ultrasound is a non-invasive evaluation of subclinical atherosclerosis and a predictor of cardiovascular events. However, ultrasound examinations are operator-dependent. In the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), ultrasound images have been acquired from more than 10,000 participants. In this article, we describe the reproducibility of carotid intima-media thickness (CIMT), carotid plaque detection, and carotid plaque score (defined as the number of arterial sites with plaques) using ELSA-Brasil protocol, in a subset of 118 participants. Two board-certified radiologists and a trained technician read carotid images. We calculated intra- and inter-observer intraclass correlation (ICC) for CIMT values. We also present kappa coefficients for plaque detection and weighted kappa coefficients for carotid plaque score. Participants were aged 58.2±6.6 years, and 60 (50.8%) were men. For common carotid artery CIMT measurements, intra- and inter-observer ICC values were very good to excellent, ranging from 0.90 (95% confidence interval [95%CI]: 0.72-0.95) to 0.98 (95%CI: 0.97-0.99). For carotid plaque, intra- (0.96 [95%CI: 0.96-0.96]) and inter- (0.99 [95%CI: 0.99-0.99]) observer weighted kappa coefficients were very good. Intra- and inter-observer Kappa coefficients for the presence of plaques by site were good to very good, ranging from 0.69 to 1.00. In conclusion, we found very good reproducibility for carotid plaque score and CIMT measurements in the ELSA-Brasil at baseline. These results are comparable to the best findings from similar large cohorts that analyzed carotid ultrasound data.

The association between subclinical thyroid dysfunctions and autonomic modulation changes has been described by many studies with conflicting results. We aimed to analyze the association between subclinical hyperthyroidism (SCHyper), subclinical hypothyroidism (SCHypo), and heart rate variability (HRV) using the baseline from ELSA-Brasil. SCHyper and SCHypo were classified by use of medication to treat thyroid disorders, thyrotropin levels respectively above and under the reference range, and normal free thyroxine levels. For HRV, the participants underwent 10 min in supine position and the R-R intervals of the final 5 min were selected for analysis. We first used linear regression models to report crude data and then, multivariate adjustment for sociodemographic (age, sex, and race) and cardiovascular risk factors (hypertension, dyslipidemia, diabetes, smoking, body mass index, use of alcohol, and leisure physical activity) using the euthyroid group as reference. From 9270 subjects (median age, 50; interquartile range: 44-56), 8623 (93.0%) were classified as euthyroid, 136 (1.5%) as SCHyper, and 511 (5.5%) as SCHypo. Compared to euthyroid subjects, SCHyper participants presented significantly higher heart rate (68.8 vs 66.5 for euthyroidism, P=0.007) and shorter R-R intervals (871.4 vs 901.6, P=0.007). Although SCHyper was associated with lower standard deviation of NN interval (SDNN) (β: -0.070; 95% confidence interval (95%CI): -0.014 to -0.009) and low-frequency (LF) (β: -0.242, 95%CI: -0.426 to -0.058) compared to the euthyroid group, these differences lost significance after multivariate adjustment for confounders. No significant differences were found for HRV in SCHypo. No association was found between HRV and SCHyper or SCHypo compared to euthyroid subjects in this sample of apparently healthy subjects.

Data on the association between subclinical thyroid dysfunction and coronary artery disease (CAD) is scarce. We aimed to analyze the association between thyroid function and CAD using baseline data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). We included subjects with normal thyroid function (0.4-4.0 mIU/L, and normal free thyroxine, FT4, or 0.8 to 1.9 ng/dL), subclinical hypothyroidism (SCHypo; TSH>4.0 mIU/L and normal FT4), and subclinical hyperthyroidism (SCHyper; TSH<0.4 mIU/L and normal FT4) evaluated by coronary computed tomography angiography. We excluded individuals using medications that interfere in thyroid function or with past medical history of cardiovascular disease. Logistic regression models evaluated the presence of CAD, segment involvement score (SIS) >4, and segment severity score (SSS) >4 of coronary arteries as the dependent variables, and quintiles of TSH and FT4 as the independent variables, adjusted for demographical data and cardiovascular risk factors. We included 767 subjects, median age 58 years (IQR=55-63), 378 (49.3%) women, 697 euthyroid (90.9%), 57 (7.4%) with SCHypo, and 13 (1.7%) with SCHyper. No association between TSH and FT4 quintiles and CAD prevalence was noted. Similarly, no association between TSH levels and the extent or severity of CAD, represented by SIS>4 and SSS>4 were seen. Restricting analysis to euthyroid subjects did not alter the results. TSH levels were not significantly associated with the presence, extent, or severity of CAD in a middle-aged healthy population.

Allantoin is the main product of uric acid oxidation and was found to be augmented in atherosclerotic plaque in human autopsy and in animal models of atherosclerosis. Uric acid is abundant in human plasma and is prone to oxidation in inflammatory conditions such as atherosclerosis. In this study, we found a significant increase in plasma uric acid (P=0.002) and allantoin (P=0.025) in participants of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) that presented common carotid intima-media thickness (c-IMT) within the 75th percentile (c-IMT≥P75). Multiple linear regression showed an association of c-IMT with uric acid (β=0.0004, P=0.014) and allantoin (β=0.018, P=0.008). This association was independent of age, the traditional risk factor LDL/HDL ratio, and non-traditional risk factors: pulse pressure, neck circumference, and the inflammatory marker myeloperoxidase. The independent and strong association of allantoin with c-IMT shows that it might be a useful marker, along with other traditional risk factors, to evaluate an early stage of atherosclerosis.

The ankle-brachial index (ABI) is a marker of subclinical atherosclerosis related to health-adverse outcomes. ABI is inexpensive compared to other indexes, such as coronary calcium score and determination of carotid artery intima-media thickness (IMT). Our objective was to identify how the ABI can be applied to primary care. Three different methods of calculating the ABI were compared among 13,921 men and women aged 35 to 74 years who were free of cardiovascular diseases and enrolled in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). The ABI ratio had the same denominator for the three categories created (the highest value for arm systolic blood pressure), and the numerator was based on the four readings for leg systolic blood pressure: the highest (ABI-HIGH), the mean (ABI-MEAN), and the lowest (ABI-LOW). The cut-off for analysis was ABI<1.0. All determinations of blood pressure were done with an oscillometric device. The prevalence of ABI<1% was 0.5, 0.9, and 2.7 for the categories HIGH, MEAN and LOW, respectively. All methods were associated with a high burden of cardiovascular risk factors. The association with IMT was stronger for ABI-HIGH than for the other categories. The proportion of participants with a 10-year Framingham Risk Score of coronary heart disease >20% without the inclusion of ABI<1.0 was 4.9%. For ABI-HIGH, ABI-MEAN and ABI-LOW, the increase in percentage points was 0.3, 0.7, and 2.3%, respectively, and the relative increment was 6.1, 14.3, and 46.9%. In conclusion, all methods were acceptable, but ABI-LOW was more suitable for prevention purposes.

Brain-derived neurotrophic factor (BDNF) is associated with neuroplasticity and synaptic strength, and is decreased in conditions associated with chronic stress. Nevertheless, BDNF has not yet been investigated in psoriasis, a chronic inflammatory systemic disease that is exacerbated by stress. Therefore, our aim was to determine BDNF plasma levels in psoriasis patients and healthy controls. Adult patients (n=94) presenting with psoriasis for at least 1 year were enrolled, and age- and gender-matched with healthy controls (n=307) from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). Participants had neither a previous history of coronary artery disease nor current episode of major depression. BDNF plasma levels were determined using the Promega ELISA kit. A general linear model was used to compare BDNF levels in psoriasis patients and controls, with age, gender, systolic blood pressure, serum fasting glucose, blood lipid levels, triglycerides, smoking status, and body mass index examined. After adjusting for clinical and demographic variables, significantly decreased BNDF plasma levels were observed in psoriasis patients (P=0.01) (estimated marginal means of 3922 pg/mL; 95%CI=2660-5135) compared with controls (5788 pg/mL; 95%CI=5185-6442). Similar BDNF levels were found in both mild and severe cases of psoriasis. Our finding, that BDNF is decreased in psoriasis, supports the concept of a brain-skin connection in psoriasis. Further studies should determine if BDNF is increased after specific psoriasis treatments, and associated with different disease stages.

Thyroid diseases are common, and use of levothyroxine is increasing worldwide. We investigated the influence of gender, race and socioeconomic status on the diagnosis and treatment of thyroid disorders using data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), a multicenter cohort study of civil servants (35-74 years of age) from six Brazilian cities. Diagnosis of thyroid dysfunction was by thyrotropin (TSH), and free thyroxine (FT4) if TSH was altered, and the use of specific medications. Multivariate logistic regression models were constructed using overt hyperthyroidism/hypothyroidism and levothyroxine use as dependent variables and sociodemographic characteristics as independent variables. The frequencies of overt hyper- and hypothyroidism were 0.7 and 7.4%, respectively. Using whites as the reference ethnicity, brown, and black race were protective for overt hypothyroidism (OR=0.76, 95%CI=0.64-0.89, and OR=0.53, 95%CI=0.43-0.67, respectively, and black race was associated with overt hyperthyroidism (OR=1.82, 95%CI=1.06-3.11). Frequency of hypothyroidism treatment was higher in women, browns, highly educated participants and those with high net family incomes. After multivariate adjustment, levothyroxine use was associated with female gender (OR=6.06, 95%CI=3.19-11.49) and high net family income (OR=3.23, 95%CI=1.02-10.23). Frequency of hyperthyroidism treatment was higher in older than in younger individuals. Sociodemographic factors strongly influenced the diagnosis and treatment of thyroid disorders, including the use of levothyroxine.

Psoriasis is a chronic inflammatory disease that significantly impacts life quality, being associated with stress and mental disorders. We investigated whether the activity of the hypothalamic-pituitary-adrenal (HPA) axis was associated with psoriasis severity, daily life stress and anxiety, and depressive symptoms. In this ancillary study, which was part of the CALIPSO (coronary artery calcium in psoriasis) study, saliva was collected from 102 patients with psoriasis immediately upon awakening, 30, and 60 min after awakening, at 2:00 pm and at bedtime (five time points) to determine salivary cortisol levels. We used Pearson's correlation coefficient to evaluate the association of clinical and psychopathological variables with HPA activity. We found a direct correlation between bedtime cortisol and psoriasis severity evaluated by the psoriasis area severity index (PASI; r=0.39, P<0.001). No correlations between other clinical and psychopathological variables or with other cortisol assessments were observed. The findings indicated that HPA dysfunction may be present in psoriasis, as bedtime cortisol was correlated with psoriasis severity. Our study is limited by the lack of a control group; therefore, we were not able to explore whether these cortisol values were different compared with a concurrent, healthy sample.

Patients with clinical diseases often present psychiatric conditions whose pharmacological treatment is hampered due to hazardous interactions with the clinical treatment and/or disease. This is particularly relevant for major depressive disorder, the most common psychiatric disorder in the general hospital. In this context, nonpharmacological interventions could be useful therapies; and, among those, noninvasive brain stimulation (NIBS) might be an interesting option. The main methods of NIBS are repetitive transcranial magnetic stimulation (rTMS), which was recently approved as a nonresearch treatment for some psychiatric conditions, and transcranial direct current stimulation (tDCS), a technique that is currently limited to research scenarios but has shown promising results. Therefore, our aim was to review the main medical conditions associated with high depression rates, the main obstacles for depression treatment, and whether these therapies could be a useful intervention for such conditions. We found that depression is an important and prevalent comorbidity in a variety of diseases such as epilepsy, stroke, Parkinson's disease, myocardial infarction, cancer, and in other conditions such as pregnancy and in patients without enteral access. We found that treatment of depression is often suboptimal within the above contexts and that rTMS and tDCS therapies have been insufficiently appraised. We discuss whether rTMS and tDCS could have a significant impact in treating depression that develops within a clinical context, considering its unique characteristics such as the absence of pharmacological interactions, the use of a nonenteral route, and as an augmentation therapy for antidepressants.

Genomics is expanding the horizons of epidemiology, providing a new dimension for classical epidemiological studies and inspiring the development of large-scale multicenter studies with the statistical power necessary for the assessment of gene-gene and gene-environment interactions in cancer etiology and prognosis. This paper describes the methodology of the Clinical Genome of Cancer Project in São Paulo, Brazil (CGCP), which includes patients with nine types of tumors and controls. Three major epidemiological designs were used to reach specific objectives: cross-sectional studies to examine gene expression, case-control studies to evaluate etiological factors, and follow-up studies to analyze genetic profiles in prognosis. The clinical groups included patients' data in the electronic database through the Internet. Two approaches were used for data quality control: continuous data evaluation and data entry consistency. A total of 1749 cases and 1509 controls were entered into the CGCP database from the first trimester of 2002 to the end of 2004. Continuous evaluation showed that, for all tumors taken together, only 0.5% of the general form fields still included potential inconsistencies by the end of 2004. Regarding data entry consistency, the highest percentage of errors (11.8%) was observed for the follow-up form, followed by 6.7% for the clinical form, 4.0% for the general form, and only 1.1% for the pathology form. Good data quality is required for their transformation into useful information for clinical application and for preventive measures. The use of the Internet for communication among researchers and for data entry is perhaps the most innovative feature of the CGCP. The monitoring of patients' data guaranteed their quality.

Previous genetic association studies have overlooked the potential for biased results when analyzing different population structures in ethnically diverse populations. The purpose of the present study was to quantify this bias in two-locus association studies conducted on an admixtured urban population. We studied the genetic structure distribution of angiotensin-converting enzyme insertion/deletion (ACE I/D) and angiotensinogen methionine/threonine (M/T) polymorphisms in 382 subjects from three subgroups in a highly admixtured urban population. Group I included 150 white subjects; group II, 142 mulatto subjects, and group III, 90 black subjects. We conducted sample size simulation studies using these data in different genetic models of gene action and interaction and used genetic distance calculation algorithms to help determine the population structure for the studied loci. Our results showed a statistically different population structure distribution of both ACE I/D (P = 0.02, OR = 1.56, 95% CI = 1.05-2.33 for the D allele, white versus black subgroup) and angiotensinogen M/T polymorphism (P = 0.007, OR = 1.71, 95% CI = 1.14-2.58 for the T allele, white versus black subgroup). Different sample sizes are predicted to be determinant of the power to detect a given genotypic association with a particular phenotype when conducting two-locus association studies in admixtured populations. In addition, the postulated genetic model is also a major determinant of the power to detect any association in a given sample size. The present simulation study helped to demonstrate the complex interrelation among ethnicity, power of the association, and the postulated genetic model of action of a particular allele in the context of clustering studies. This information is essential for the correct planning and interpretation of future association studies conducted on this population.