Nutritional evaluation follow-up of the 1982 birth cohort, Pelotas, Southern Brazil

Abstracts

OBJECTIVE: To estimate the prevalence of over/underweight and its association with demographic and socioeconomic factors. METHODS: Longitudinal cohort study of youths born in 1982 in Pelotas, Southern Brazil. In 2004-5 we interviewed 4,198 of the 5,914 cohort subjects, obtaining weight and stature measurements that were used to calculate body mass index (BMI). Underweight was defined as BMI lower than 18,5 kg/m²; overweight as BMI between 25 and 30kg/m²; and obesity as BMI IMC > 30kg/m². The effects of socioeconomic (family income and schooling) and demographic (skin color) variables, birthweight, and breastfeeding on underweight, overweight, and obesity were analyzed separately for men and women using Poisson regression. RESULTS: Prevalence of underweight, obesity, and overweight were 6.0%, 8.2%, and 28.9%, respectively. In adjusted analysis, only birthweight remained associated with underweight among men and women. Poor men showed higher risk of underweight, but were protected from obesity and overweight. By contrast, risk of obesity and overweight was higher among poor women. CONCLUSIONS: The present results underscore the importance of socioeconomic determinants on nutritional status, with special emphasis on the distinct effects these factors have among men and women in different nutritional conditions.

Adult; Nutrition Assessment; Obesity; Deficiency Diseases; Socioeconomic Factors; Cohort Studies; Brazil

OBJETIVO: Estimar a prevalência de desnutrição por déficit ou excesso de peso e sua associação com fatores demográficos e socioeconômicos. MÉTODOS: Estudo longitudinal de coorte de jovens nascidos em 1982 em Pelotas, RS. Em 2004-5 foram entrevistados 4.198 dos 5.914 indivíduos dessa coorte, que tiveram suas medidas de peso e estatura coletadas para cálculo do índice de massa corporal (IMC). Definiu-se baixo peso pelo valor de IMC inferior a 18,5 kg/m²; excesso de peso, pelo IMC entre 25 e 30kg/m²; e obesidade pelo IMC>30kg/m². Os efeitos de variáveis socioeconômicas (renda familiar e escolaridade), demográfica (cor da pele), peso ao nascer e amamentação sobre baixo peso, excesso de peso e obesidade foram analisados utilizando regressão de Poisson separadamente para homens e mulheres. RESULTADOS: As prevalências de baixo peso, obesidade e excesso de peso foram 6,0%, 8,2% e 28,9%, respectivamente. Na análise ajustada somente o peso ao nascer manteve-se associado com baixo peso em homens e mulheres. Homens pobres tiveram maior risco de baixo peso, mas ficaram protegidos da obesidade e do excesso de peso. Por outro lado, o risco de obesidade e excesso de peso foi maior entre as mulheres pobres. CONCLUSÕES: Os resultados reforçam a importância da determinação socioeconômica sobre o estado nutricional, chamando atenção como esses fatores agem de forma distinta em homens e mulheres de diferentes situações nutricionais, indicando atenção no que se refere a medidas específicas na prevenção, melhorando o acesso à informação sobre educação alimentar e nutricional para toda população.

Adulto; Avaliação Nutricional; Obesidade; Deficiências Nutricionais; Fatores Socioeconômicos; Estudos de Coortes; Brasil

ORIGINAL ARTICLES

Denise P Gigante^I; Gicele C Minten^I; Bernardo L Horta^I; Fernando C Barros^II; Cesar G Victora^I

^IPrograma de Pós-Graduação em Epidemiologia. Universidade Federal de Pelotas. Pelotas, RS, Brasil

^IIPrograma de Pós-Graduação em Saúde e Comportamento. Universidade Católica de Pelotas. Pelotas, RS, Brasil

Correspondence

ABSTRACT

OBJECTIVE: To estimate the prevalence of over/underweight and its association with demographic and socioeconomic factors.

METHODS: Longitudinal cohort study of youths born in 1982 in Pelotas, Southern Brazil. In 2004-5 we interviewed 4,198 of the 5,914 cohort subjects, obtaining weight and stature measurements that were used to calculate body mass index (BMI). Underweight was defined as BMI lower than 18,5 kg/m²; overweight as BMI between 25 and 30kg/m²; and obesity as BMI IMC > 30kg/m². The effects of socioeconomic (family income and schooling) and demographic (skin color) variables, birthweight, and breastfeeding on underweight, overweight, and obesity were analyzed separately for men and women using Poisson regression.

RESULTS: Prevalence of underweight, obesity, and overweight were 6.0%, 8.2%, and 28.9%, respectively. In adjusted analysis, only birthweight remained associated with underweight among men and women. Poor men showed higher risk of underweight, but were protected from obesity and overweight. By contrast, risk of obesity and overweight was higher among poor women.

CONCLUSIONS: The present results underscore the importance of socioeconomic determinants on nutritional status, with special emphasis on the distinct effects these factors have among men and women in different nutritional conditions.

Descriptors: Adult. Nutrition Assessment. Obesity, epidemiology. Deficiency Diseases, epidemiology. Socioeconomic Factors. Cohort Studies. Brazil.

RESUMEN

OBJETIVO: Estimar la prevalencia de desnutrición por déficit o exceso de peso y su asociación con factores demográficos y socioeconómicos.

MÉTODOS: Estudio longitudinal de cohorte de jóvenes nacidos en 1982 en Pelotas (Sur de Brasil). En 2004-5 fueron entrevistados 4.198 de los 5.914 individuos de esa cohorte, que tuvieron sus medidas de peso y estatura colectadas para cálculo del índice de masa corporal (IMC). Se definió bajo peso por el valor de IMC inferior a 18,5 kg/m²; exceso de peso por el IMC entre 25 y 30 30kg/m²; y obesidad por el IMC>30kg/m². Los efectos de variables socioeconómicas (renta familiar y escolaridad), demográfica (color de piel), peso al nacer y amamantamiento sobre bajo peso, exceso de peso y obesidad fueron analizados utilizando regresión de Poisson separadamente para hombres y mujeres.

RESULTADOS: Las prevalencias de bajo peso, obesidad y exceso de peso fueron 6,0%, 8,2% y 28,9%, respectivamente. En el análisis ajustado solamente el peso al nacer se mantuvo asociado con bajo peso en hombres y mujeres. Hombres pobres tuvieron mayor riesgo de bajo peso, pero estuvieron protegidos de la obesidad y del exceso de peso. Por otro lado, el riesgo de obesidad y exceso de peso fue mayor entre las mujeres pobres.

CONCLUSIONES: Los resultados refuerzan la importancia de la determinación socioeconómica sobre el estado nutricional, llamando la atención de cómo esos factores actúan de forma distinta en hombres y mujeres de diferentes situaciones nutricionales, indicando atención en lo que se refiere a medidas específicas en la prevención, mejorando el acceso a la información sobre educación alimentar y nutricional para toda la población.

Descriptores: Adulto. Evaluación Nutricional. Obesidad, epidemiología. Enfermedades Carenciales, epidemiología. Factores Socioeconómicos. Estudios de Cohortes. Brasil.

INTRODUCTION

Beginning in the 1960's, the World Health Organization (WHO) has proposed nutritional evaluation systems for the early detection of nutritional problems highly prevalent in different settings as a basis for developing preventive and control measures.⁵

In 1995, WHO proposed the use of the body mass index (BMI) as a definition of various degrees of underweight, overweight, and obesity.²¹

Nutritional evaluation across long time periods and in different populations has provided evidence of a nutritional transition, linked to the processes of demographic and epidemiologic change. In contrast to developed countries, however, increased occurrence of obesity and overweight in several developing countries is taking place alongside the persistence of problems related to underweight.¹²

Global estimates for 2005 indicated that 1.6 billion adults were classified as overweight, and 400 million as obese. Although these problems were initially described only among adults, they currently affect also children and adolescents, with an estimated 20 million overweight children aged up to five years worldwide.ª Almost one-half of the global burden of disease is due to problems related to nutritional status, be it over or underweight, as determined both by BMI and diet.

METHODS

The present analysis refers to the birth cohort study initiated in Pelotas, Southern Brazil, in Southern Brazil, in 1982. Detailed methodological information on this study has been published previously (Victora et al^17,18 2003 e 2006; Barros et al²).

In 2004-5, 4,297 of the 5,914 youths born in 1982 were visited for nutritional evaluation. We excluded from this analysis 90 women in the third to ninth months of pregnancy, representing 4.3% of the women in the sample. Therefore, our results pertain to 4,198 youths whose anthropometric information allowed for nutritional evaluation. Weight was measured using portable electronic scales (Seca uniscale^®, Alemanha) with 100g precision. Aluminum anthropometers were used to obtain height measures. Weight and height measures were obtained following the recommendations of Lohmann et al,⁸ and all interviewers were trained in obtaining these measures. Underweight, overweight, and obesity were defined based on BMI (weight divided by height in meters squared), according to criteria established by WHO.²¹ Subjects with BMI<18.5 kg/m² were classified as underweight; those with BMI between 25 and 30kg/m², as overweight, and those with BMI>30 kg/m², as obese.

Independent variables included demographic factors (sex and skin color); socioeconomic factors (family income in 1982, change in income from 1982 to 2004-5, and schooling); birthweight, and duration of breastfeeding. The variable change in income was constructed based on the distribution in terciles of income distribution in 1982 and 2004-5; subjects were classified into the following categories: always poor (those in the lowest family income tercile in both 1982 and 2004-5); poor → non poor (lowest tercile in 1982 to middle or upper tercile in 2004-5); non poor → poor (middle or upper tercile in 1982 to lower tercile in 2004-5); and never poor (middle or upper tercile in both 1982 and 2004-5).

We used Poisson regression to investigate the effect of these variables on the occurrence of underweight, overweight, and obesity. Prevalence ratios and their respective confidence intervals were presented as estimates of risk. Risks were compared using the Wald test for heterogeneity or linear trend when applicable. Analysis was stratified by sex and adjusted according to a hierarchic analysis model including skin color and family income in 1982 (or, in an alternative analysis, change in income in the period) in the first level; birthweight in the second level; and breastfeeding and youth's schooling in the third level. Results were adjusted for any variables in the preceding level associated with the outcomes with p<0.20.

Verbal informed consent was obtained from guardians in study phases between 1982 and 1986, following common practice at the time, when an ethics committee was not available at the Federal University of Pelotas. In more recent stages, the study received the approval of the university's Research Ethics Committee, affiliated to the Conselho Nacional de Ética em Pesquisa (National Research Ethics Committee - CONEP), and written informed consent was obtained.

RESULTS

Mean BMI was 23.6±4.4 kg/m² for the entire sample, and differed significantly between men (23.8±4.1 kg/m²) and women (23.4±4.7 kg/m²). Prevalence of underweight, obesity, and overweight were, respectively, 6.0%, 8.2%, and 28.9% in the entire sample, and also varied according to sex.

Prevalence of underweight was not associated with skin color, family income, or youth's schooling (Table 1), but was inversely associated with birthweight. Though not statistically significant, there was an association between underweight and change in income between 1982 and 2004-5 among men, with higher prevalence among those whose families showed socioeconomic improvement. On the other hand, an association between underweight and duration of breastfeeding was found only among women, with higher prevalence among those weaned within the first month after birth. Adjusted analysis (Table 2) for men showed that the crude effect of lower birthweight on prevalence of nutritional deficit at age 23 years remains. Regarding income-related variables, whereas differences in categories of income change lost statistical significance (p=0.06) after adjustment for skin color, this same adjustment showed a linear effect of lower family income in 1982 on greater prevalence of underweight among men.

Tables 3 and 4 present crude prevalences of obesity and overweight, respectively, for each independent variable. Associations differed according to sex. For skin color, prevalences of obesity and overweight were greater among black or mixed women, but showed no difference among men. Prevalence of obesity and overweight was greater among men of high socioeconomic level and poor women. Greater prevalence of overweight and obesity were also seen among subjects with higher birthweight (with the exception of obesity among women). Obesity and overweight were more prevalent among men who were breastfed for 6 to 8.9 months (p=0.05) and women who were breastfed for 9 to 11.9 months (p=0.03), respectively. These prevalences were also higher among women with lesser schooling, whereas overweight was more frequent among men with greater schooling.

Adjusted results for obesity and overweight were similar. Table 5 presents only the results of crude and adjusted analysis of the effects of independent variables on overweight. In the hierarchic analysis, associations with skin color, family income, change in income, and birthweight were maintained. The association between breastfeeding and overweight observed among women disappeared after control for the effect of the distal variable socioeconomic conditions at birth or of the intermediate variable birthweight. The association between schooling and overweight among men vanished after adjustment for a hierarchically superior socioeconomic variable, such as family income, and for birthweight. This same association was inverse among women, and remained significant after adjustment.

In the case of obesity, adjusted analyses showed similar associations, with the exception of birthweight, which was positively associated with obesity only among men (data not shown).

In adjusted analysis, risk of obesity or overweight fell by half among poorer men. Poorer women showed two to ten-fold greater risk of overweight or obesity when compared to those coming from families who earned over ten minimum wages.

DISCUSSION

Our results show that over one-third of young adults from the 1982 birth cohort are malnourished, defined as BMI below (6% of the cohort) or above (29%) levels considered normal.

Among women, prevalence of underweight (7.5%) was similar to that seen in the state of Rio Grande do Sul (6.7%), but lower than the national prevalence (12.0%) reported for women aged 20-24 years in the 2002-2003 Pesquisa Nacional de Orçamentos Familiares (National Household Budget Survey - POF).^c Obesity was more frequent among cohort subjects than among women from Rio Grande do Sul (7.4%) or from Brazil as a whole (4.7%).^c

Among men aged 20-24 years, prevalence of underweight reported by the POF was 4.4% for Brazil and 3.4% for the state of Rio Grande do Sul, compared to 4.9% in the cohort. Prevalence of obesity was higher in the cohort (7.5%) than in the state (5.2%) or the country (3.1%).^c

The results of the POFª for the Brazilian population show an inverse relation between family income and weight among women. Prevalence of underweight was always higher among women with per capita family income below one-quarter of a minimum wage (8.5%). Among men, prevalence was below 5% across all socioeconomic groups.^c However, in the present study, we found no association between income and underweight in women, but an inverse trend for this relationship was seen among men.

The association between birthweight and underweight among cohort subjects confirmed the results of studies showing a positive correlation between birthweight and adult BMI.^11,13,15 As to duration of breastfeeding, we are unable to present comparative data, since the literature reviewed is deficient in this particular aspect.

Regarding factors associated to obesity and overweight, the higher risk found among black and mixed women confirms results reported in the United States.^4,9 Studies carried out in Brazilian cities show contradictory results. A cross-sectional, population-based study of adults from Pelotas⁶ failed to detect an association between obesity and skin color. In Rio de Janeiro, gain of weight across a ten-year period was found to be greater among black and mixed women than among white women, even after adjustment for socioeconomic conditions throughout life.³

In less developed countries, overweight or obesity were historically more frequent among those of higher socioeconomic level.¹⁴ However, Monteiro et al¹⁰ (2004) showed that, in middle-income countries, overweight is becoming increasingly frequent among the poor, and that this inversion occurs earlier for women than for men.

In Brazil, in 1989, overweight and obesity were more prevalent among rich men and women.

Birthweight was positively associated with overweight among men and women from our cohort, and with prevalence of obesity among men, confirming previous findings.^1,16 The same association was also reported for our cohort when subjects were 15 and 18 years old.^11,15

A hypothesis has been proposed according to which weight at birth would contribute mostly to the acquisition of lean mass rather than fat mass.^15,16,20 However, we do not have sufficient data on the evolution of body composition among members of our cohort to allow us to identify the time of onset of this nutritional disorder. We thus chose to use Poisson regression in order to estimate risks associated with the studied outcomes in terms of prevalence ratios.

The inverse association between schooling and overweight or obesity among women corroborates previous findings.^6,10 For men, however, data in the literature are controversial. Positive associations have been observed in seven of the studies included in a review of surveys from developing countries,¹⁰ but another seven studies did not detect such association, as was the case for our cohort. In the hierarchic analysis model used in the present study, the effect of a distal socioeconomic variable such as family income at birth would be related to the level of schooling of the youth. However, one must also consider the effect of current income, given that risk of overweight was greater among those whose income decreased between 1982 and 2004-5.

A meta-analysis study has shown that subjects who were breastfed showed lower frequency of overweight and obesity, irrespective of duration of breastfeeding.⁷ In the present study, no association was detected, confirming previous analyses of this same cohort carried out when subjects were acolescents.¹⁷

The high prevalence of overweight and obesity among young adults shows a pressing need for adequate prevention and control measures in order to prevent the emergence of morbidities related to nutritional status. Intervention priority should be given to subgroups among which nutritional problems are more frequent, namely men of all income levels and poor women. Although obesity and overweight were more frequent among men from higher-income families, no association was found with respect to schooling. This aspect should be considered when planning intervention at the educational level.

As to underweight, the need for interventions aimed at preventing this condition among the poor is questionable, especially given the possibility of consequent increases in overweight and obesity, especially among women.

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Nutritional evaluation follow-up of the 1982 birth cohort, Pelotas, Southern Brazil

Evaluación nutricional de adultos de la cohorte de nacimientos de 1982, Pelotas, Sur de Brasil

^b

The aim of the present article was to estimate the prevalence of malnutrition - either by over or underweight - and determine its associated factors in a cohort of subjects followed since their birth in 1982.

^d

Results from the POF

^c show a direct relationship between income and obesity among men, but not among women; however, greater prevalences among women are found in the intermediate income groups. Increased prevalence of overweight has been observed among men from all of the country's Regions and of all income levels between 1989 and 2003.

^c Among women, prevalence has increased in the country's Northeast Region and among families with lower monthly income, whereas in the remaining regions and in higher-income classes prevalence of overweight has either remained stable or declined (IBGE 2004).

^c

Publication Dates

• Publication in this collection
  06 Jan 2009
• Date of issue
  Dec 2008

History

• Accepted
  19 Sept 2008
• Reviewed
  10 Sept 2008
• Received
  10 Oct 2007