Bioelectrical impedance analysis: population reference values for phase angle by age and sex

BACKGROUND

Phase angle is an indicator based on reactance and resistance obtained from bioelectrical impedance analysis (BIA). Although its biological meaning is still not clear, phase angle appears to have an important prognostic role.

OBJECTIVE

The aim of this study was to estimate population averages and SDs of phase angle that can be used as reference values.

DESIGN

BIA and other methods used to evaluate body composition, including hydrodensitometry and total body water, were completed in 1967 healthy adults aged 18-94 y. Phase angle was calculated directly from body resistance and reactance, and fat mass (FM) was estimated from the combination of weight, hydrodensitometry, and total body water by using the 3-compartment Siri equation. Phase angle values were compared across categories of sex, age, body mass index (BMI), and percentage FM.

RESULTS

Phase angle was significantly (P < 0.001) smaller in women than in men and was lower with greater age (P < 0.001). Phase angle increased with an increase in BMI and was significantly inversely associated with percentage fat in men. Phase angle was significantly predicted from sex, age, BMI, and percentage FM in multiple regression models.

CONCLUSIONS

Phase angle differs across categories of sex, age, BMI, and percentage fat. These reference values can serve as a basis for phase angle evaluations in the clinical setting.

Bioelectrical impedance analysis in clinical practice: a new perspective on its use beyond body composition equations

PURPOSE OF REVIEW

The bioelectrical impedance analysis is not a direct method for estimating body composition. Its accuracy depends on regression equations, and recent papers have suggested that this approach should not be used in several clinical situations. Another option is to obtain information about the electrical properties of tissues by using raw bioelectrical impedance measurements, resistance and reactance. They can be expressed as a ratio (phase angle) or as a plot (bioelectrical impedance vector analysis). This review describes their use in clinical practice.

RECENT FINDINGS

The phase angle changes with sex and age. It is described as a prognostic tool in many clinical situations. There are some controversies about considering it as a nutritional marker. Studies in burn victims and sickle-cell disease corroborate its ability to evaluate cell membrane function. Bioelectrical impedance vector analysis allows a semi-quantitative estimation of body composition from information from tissue hydration and soft-tissue mass in a plot. It can be used in healthy individuals or patients, for a population or individual evaluation of fluid imbalance or an assessment of soft-tissue mass. It has also been used as a prognostic tool in dialysis and cancer patients.

SUMMARY

The phase angle can be considered a global marker of health, and future studies are needed to prove its utility in intervention studies. Bioelectrical impedance vector analysis has increased its utility in clinical practice, even when the equations may be inaccurate for body composition analysis.

Utilização de medicamentos para tratamento de infecções respiratórias na comunidade

OBJETIVO: Descrever o perfil dos tratamentos medicamentosos usados nas infecções respiratórias, com o intuito de auxiliar o estabelecimento de ações que otimizem o manejo dessas importantes entidades nosológicas. MÉTODOS: Foi realizado um estudo transversal de base populacional que incluiu uma amostra de 6.145 indivíduos residentes na zona urbana do município de Pelotas, RS, localizado na Região Sul do Brasil, no período de 1999/2000. Para coleta de dados foram utilizadas entrevistas com questionário estruturado contendo perguntas sobre o uso de medicamentos para o tratamento de infecções respiratórias nos 30 dias que antecederam a entrevista. Para análise estatística dos dados utilizou-se o teste de qui-quadrado de Pearson. RESULTADOS: A prevalência global de infecções respiratórias tratadas foi de 6,3%. Ela foi maior nas crianças de até quatro anos de idade (18%) e menor nos idosos (60 anos ou mais) (3%; p<0,001). As faringoamigdalites foram as infecções mais freqüentemente tratadas (41%). Cinqüenta e nove por cento dos entrevistados usaram antimicrobianos no tratamento de infecções respiratórias. O antimicrobiano mais utilizado foi a amoxicilina (38%). Entre as drogas sintomáticas utilizadas, os antiinflamatórios não esteróides foram os mais citados (27%). CONCLUSÕES: A maioria das infecções respiratórias para as quais se utilizou algum medicamento são tratadas com antimicrobianos, apesar de a etiologia viral ser a mais prevalente nessas doenças. O uso excessivo dessas drogas, além de aumentar os custos dos tratamentos, pode levar à emergência de resistência bacteriana aos antimicrobianos mais freqüentemente utilizados.

Utilização de medicamentos em adultos: prevalência e determinantes individuais

OBJETIVO: Estudar os padrões de utilização de medicamentos, classificando-os por grupos farmacológicos e verificando os determinantes individuais desse uso. MÉTODOS: Delineamento transversal de base populacional. Amostra composta por 3.182 indivíduos com 20 anos de idade ou mais, residentes na região urbana do município de Pelotas, RS. O processo de amostragem foi conduzido em múltiplos estágios. O instrumento foi um questionário estruturado, utilizando um período recordatório de 15 dias e aplicado através de entrevistas individuais. Na análise bruta, foram utilizados os seguintes testes: qui-quadrado para comparação de proporções, teste t para comparação de médias e o teste de tendência linear. A análise ajustada foi conduzida através de uma regressão de Poisson. RESULTADOS: A prevalência de uso global de medicamentos foi de 65,9%. Os seguintes grupos apresentaram maiores prevalências de utilização de medicamentos após análise ajustada: mulheres, idosos, indivíduos de nível econômico mais elevado e com pior autopercepção de saúde. Os grupos farmacológicos mais utilizados foram os analgésicos, antiinflamatórios e anti-hipertensivos. CONCLUSÕES: A prevalência de uso de medicamentos foi superior às encontradas em outros estudos nacionais e internacionais. O estudo dos determinantes individuais de utilização de medicamentos indica os grupos mais sujeitos ao uso excessivo, o que pode embasar estratégias específicas para diminuir a utilização nesses grupos, tais como políticas mais restritivas para prescrição e venda de medicamentos.

Utilização de antimicrobianos em uma população urbana

OBJETIVO: A emergência de cepas microbianas com crescentes níveis de resistência aos antimicrobianos tem sido objeto de preocupação em todo o mundo. Entre as causas apontadas para o fenômeno, está o uso abusivo e indiscriminado de drogas antimicrobianas. O presente estudo visa fornecer informações sobre o padrão de utilização dessas drogas em uma população urbana. MÉTODOS: Em um estudo transversal, de base populacional, 6.145 indivíduos de todas as idades residentes na zona urbana de Pelotas, Rio Grande do Sul, foram entrevistados sobre o uso de antimicrobianos nos 30 dias que antecederam a entrevista. RESULTADOS: A prevalência global de utilização de antimicrobianos encontrada foi de 8%. Essa foi maior entre as crianças até quatro anos de idade (14%; p<0,001), entre as mulheres (9%; p=0,004) e entre os separados/divorciados (10%; p=0,02). As indicações clínicas principais foram infecções do trato respiratório (50%), infecções do trato urinário (16%) e infecções dentárias (9%). As drogas antimicrobianas mais utilizadas foram as penicilinas (41%), as sulfas (17%) e as tetraciclinas (8%). CONCLUSÕES: O uso intensivo de drogas de última geração, temido por muitos estudiosos do tema, não foi confirmado. A possibilidade de redução da utilização de antimicrobianos existe, uma vez que as afecções do trato respiratório (a principal indicação para o seu uso) são, em sua maioria, de etiologia viral, e seu tratamento não se beneficia com drogas antimicrobianas.

Alternatives for logistic regression in cross-sectional studies: an empirical comparison of models that directly estimate the prevalence ratio

BACKGROUND

Cross-sectional studies with binary outcomes analyzed by logistic regression are frequent in the epidemiological literature. However, the odds ratio can importantly overestimate the prevalence ratio, the measure of choice in these studies. Also, controlling for confounding is not equivalent for the two measures. In this paper we explore alternatives for modeling data of such studies with techniques that directly estimate the prevalence ratio.

METHODS

We compared Cox regression with constant time at risk, Poisson regression and log-binomial regression against the standard Mantel-Haenszel estimators. Models with robust variance estimators in Cox and Poisson regressions and variance corrected by the scale parameter in Poisson regression were also evaluated.

RESULTS

Three outcomes, from a cross-sectional study carried out in Pelotas, Brazil, with different levels of prevalence were explored: weight-for-age deficit (4%), asthma (31%) and mother in a paid job (52%). Unadjusted Cox/Poisson regression and Poisson regression with scale parameter adjusted by deviance performed worst in terms of interval estimates. Poisson regression with scale parameter adjusted by chi2 showed variable performance depending on the outcome prevalence. Cox/Poisson regression with robust variance, and log-binomial regression performed equally well when the model was correctly specified.

CONCLUSIONS

Cox or Poisson regression with robust variance and log-binomial regression provide correct estimates and are a better alternative for the analysis of cross-sectional studies with binary outcomes than logistic regression, since the prevalence ratio is more interpretable and easier to communicate to non-specialists than the odds ratio. However, precautions are needed to avoid estimation problems in specific situations.

[Traffic accidents resulting in injuries: underreporting, characteristics, and case fatality rate]

In order to describe traffic accidents in a medium-sized Brazilian city and compare the risks of injury and death among different types of vehicles and pedestrians, all traffic accidents identified through police and hospital emergency records were registered for two years Deaths by such accidents were identified and confirmed through the coroner's office. The number of registered vehicles in the municipality was obtained through the State traffic authority. Morbidity and mortality rates were calculated and tests of association between selected variables performed. There was a relevant underreporting of accidents by the police (up to 53%), which varied according to the type of accident and time of occurrence. The highest case fatality rate was observed among bicyclists and pedestrians (around 5%), followed by motorcyclists (3%). Pedestrians formed the highest contingent of deaths. Motorcyclists had an eightfold risk of dying, a fourfold risk of injury, and a twofold risk of running over pedestrians as compared to automobile drivers. We conclude that pedestrians and motorcyclists are priority groups for interventions aimed at reducing injury and death from traffic accidents.

Outpatient health service utilization and associated factors: a population-based study

OBJECTIVE

To identify factors that lead people to visit a doctor in Brazil and assess differences between socioeconomic groups.

METHODS

A cross-sectional study comprising 1,260 subjects aged 15 or more was carried out in southern Brazil. Demographic, socioeconomic, health needs and regular source of care data were analyzed concerning visits to a doctor within two months from the interview. Adjusted prevalence ratios and 95% confidence intervals were calculated using Poisson regression.

RESULTS

Adjusted PR showed that women having stressful life events, health insurance, and a regular doctor increased the outcome. A dose-related response was found with self-reported health, and the probability of visiting a doctor increased with health needs. Analysis in the chronic disease group revealed that uneducated lower income subjects had a 62% reduction in the chance of visiting a doctor compared to uneducated higher income ones. However, as it was seen a significant interaction between income and education, years of schooling increased utilization in this group.

CONCLUSIONS

Results suggest the existence of health inequity in the poorest group that could be overcome with education. Specific measures reinforcing the importance of having a regular doctor may also improve access in the underserved group.

Can bioelectrical impedance analysis identify malnutrition in preoperative nutrition assessment?

OBJECTIVE

Malnutrition is characterized by changes in cellular membrane integrity and alterations in fluid balance, both of which can be detected by bioelectrical impedance analysis (BIA). We investigated whether BIA-measured variables could detect malnutrition, as defined by the Subjective Global Assessment (SGA), in preoperative surgical patients.

METHODS

We prospectively evaluated 279 patients hospitalized for elective gastrointestinal surgery during the first 72 h after admission. BIA estimates were used to derive body cell mass, ratio of extracellular mass to body cell mass, and phase angle. Malnutrition diagnosed with these measures was compared with the SGA score. Receiver operating characteristic curves also were formulated to explore alternative cutoff points for one measure, phase angle.

RESULTS

A linear trend for means across SGA categories was found for all indicators used, except percentage of body cell mass. However, there was only fair overall agreement between SGA and BIA estimates. The receiver operating characteristic curves for phase angle suggested that the test was too sensitive or too specific. No alternative cutoff points resulted in suitable tests that could provide an alternative to SGA.

CONCLUSIONS

Although not in close agreement with SGA, the results suggested that there are some alterations in tissue electrical properties with malnutrition that can be detected by BIA. New cutoff points may be needed for application of BIA as a complementary method in the nutrition assessment of surgical patients.

[Prevalence of near vision deficiency and related factors: a population-based study]

The objective of this article was to estimate the prevalence of presbyopia in adults > or = 30 years and explore associated characteristics such as demographic, socioeconomic, and individual variables. A cross-sectional, population-based study was performed with 3,007 adults > or = 30 years in Pelotas, Rio Grande do Sul, Brazil. Near vision acuity was evaluated using the Jaeger table, and other variables were investigated using standardized, pre-coded questionnaires. Prevalence of presbyopia was 54.7%. When visual acuity was measured using visual corrective means, prevalence was 29.34%. Age and female gender were associated with the outcome variable after controlling for confounding. Some 42.4% of the sample reported not requiring near vision for routine daily tasks. The conclusion was that presbyopia displays a high prevalence in the adult population and is directly related to increasing age, especially 45 years of age and appearing earlier in women. In some 30% of individuals who already use visual corrective means, the latter are ineffective for near vision.

[Risk factors for accidental injuries in preschool children]

OBJECTIVE

To measure the main risk factors associated with the occurrence of accidental injuries in children aged 4-5 years.

METHODS

The study included a prospective cohort of children whose parents filled in a diary recording accidents and injuries during a period of one-month. The children represented a systematic subsample from a population-based birth cohort in southern Brazil. The outcome was the number of reported injuries per child during one month. Multivariate analysis (Poisson regression) was used to assess confounding factors.

RESULTS

The monthly frequency of accidents was 53.8%, and 48.4% of the children suffered at least one injury. Boys had 30% more injuries than girls, and white children had 70% higher incidence than non-white. Family income, parental education and maternal employment were not associated with the frequency of injuries. After adjustment of socioeconomic and environmental factors, having younger siblings was associated with a 30% higher injury rate, and living in a home made of bricks was associated with a 35% increase. The incidence of injuries appeared to be higher among children attending day-care centers and those living in periurban areas.

CONCLUSIONS

Few risk factors were associated with an increased frequency of injuries. Among them, the most amenable to intervention seems to be the presence of younger siblings. Parents should become aware of children's needs for increased attention when a younger sibling is born.

Desigualdades na utilização e no acesso a serviços odontológicos: uma avaliação em nível nacional

Para avaliar a situação de utilização e acesso aos serviços de odontologia no Brasil e estudar diferenciais entre os estratos socioeconômicos, utilizaram-se dados da Pesquisa Nacional por Amostragem de Domicílios (PNAD) de 1998, realizada pelo IBGE. A análise, que levou em conta o desenho amostral, indicou um nível baixo de utilização de serviços odontológicos. Setenta e sete por cento das crianças de 0-6 anos e 4% dos adultos de 20-49 anos nunca haviam consultado um dentista. Entre estes adultos, comparando-se os 20% mais pobres com os 20% mais ricos, observou-se que o número de desassistidos era 16 vezes maior entre os primeiros. No grupo de 0-6 anos, as crianças ricas consultaram o dentista cinco vezes mais do que as pobres no ano anterior à entrevista. Cerca de 4% dos que procuraram atendimento odontológico não o obtiveram, 8% dos quais entre os mais pobres e 1% entre os mais ricos. A maioria (68%) dos atendimentos do grupo mais pobre foi financiada pelo SUS, enquanto 63% deles foram pagos pelos mais ricos. As maiores desigualdades no acesso e na utilização de serviços odontológicos foram encontradas, exatamente, nos grupos de menor acesso ou utilização. A participação do SUS nos atendimentos odontológicos é muito mais baixa do que na atenção médica.