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2 Research Unit 106, Nutrition, Food, Societies, (WHO collaborating Centre for Nutrition), Institut de Recherche pour le Développement (IRD), Montpellier, France; 3 Doctoral School 393, Public Health: Epidemiology and Biomedical Information Sciences, Université Pierre et Marie Curie, Paris 6, France; and 4 Research Unit 106, Nutrition, Food, Societies, Institut de Recherche pour le Développement (IRD), Ouagadougou, Burkina Faso
* To whom correspondence should be addressed. E-mail: mathilde.savy{at}mpl.ird.fr.
| ABSTRACT |
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| Introduction |
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| Subjects and Methods |
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350,000 inhabitants. The majority of the population belongs to the Gourmantche ethnic group. The province is particularly vulnerable because of its landlocked position, low-quality soils, and harsh climatic conditions, including scarce and erratic rainfall. Annual rainfall is
610 mm and is concentrated during the period between June and September. The year is split into 3 distinct periods: the harvest season from October to December; the postharvest season from January to April, when food is relatively abundant; and the preharvest season from May to September, during which the population faces a cereal shortage and which is also characterized by hard agricultural work and increased morbidity. Sampling. A longitudinal domestic survey was carried out in 30 villages in the province at the beginning of the cereal-shortage season (April 2003) and at the end of the cereal-shortage season of the same year (September). The sample stemmed from a previous survey carried out in March 2002 (28) for which a 2-stage sampling technique was used: first, the 30 villages were randomly selected with a probability proportional to size, and then 6 compounds were randomly selected in each village. All the women living in the selected compounds that had a child <5 y of age were included in the study. The same women were surveyed again in April and in September of 2003. In April, the sample included 550 women; 67 were lost at follow-up in September because of migration away from the study area, refusal to take part in the study, or because they died. All the women included in the study, as well as the village, compound, and household heads, verbally gave their free and informed consent to participate.
Food consumption. A qualitative recall of all foods consumed by the women during the previous 24-h period was performed in both seasons (April and September 2003). Each woman involved in the study was asked to recall all the dishes, snacks, or other foods she had eaten during this period, regardless of whether the food was eaten inside or outside the compound. From a practical point of view, we first let the woman spontaneously describe her food consumption and then we prompted her to be sure that no meal or snacks had been forgotten. Next, a detailed list of all the ingredients of the dishes, snacks, or other foods mentioned, was collected from either the person in charge of their preparation or directly from the woman being interviewed. No distinction was made between recalls made on weekdays or on weekends, insofar as weekends did not have any special importance in the context of our study. We were careful not to include atypical days (such as local feast days or celebrations) in the recall, but market days were noted and accounted for in the analysis because food consumption was likely to be different on those occasions. The interviews were conducted by 2 carefully trained fieldworkers with at least a secondary-school education. Both of them spoke French and local languages (Gourmantchema, Moore, and Fulfulde).
The information collected allowed us to calculate a dietary diversity score for each season, which was defined as the number of different food groups consumed in the 24 h preceding the recall. Because there is no internationally acknowledged recommendation for the food group classifications to be used, we decided to use a 9 foodgroup classification derived from a proposal made at a workshop on dietary diversity in Rome in October, 2004 (31): cereals, roots, tubers; pulses, nuts; vitamin Arich fruits, vegetables; other vegetables; other fruits; meat, poultry, fish; eggs; milk, dairy products; and oils, fats. Neither the frequency of consumption nor the amount of food consumed was taken into consideration. The scores were used as discrete quantitative variables and were also divided into terciles to distinguish diets of high, medium, and low diversity. The choice of cut-offs to define the terciles was based on the distribution of DDSs observed in April. The same cut-offs were applied to the DDSs measured in September.
Anthropometric measurements.
The anthropometric measurements were performed using the standardized procedures recommended by WHO (32). The women were weighed to the nearest 100 g on electronic scales with a weighing capacity of 10 to 140 kg. Their height was measured to the nearest mm with locally made portable devices equipped with height gauges (SECA 206 Bodymeter). The BMI [weight/height2 (kg/m2)] was calculated and the threshold of 18.5 kg/m2 was used to identify underweight women. Bicipital, tricipital, subscapular, and suprailiac skinfold thicknesses were measured in duplicate to the nearest 0.2 mm with a Holtain caliper according to standard Lohman procedures (33). The measurement of skinfold thickness enabled us to determine body density by applying the equation developed by Durnin and Womersley (34). To calculate the body fat percentage from body density in black subjects, we accounted for their higher lean mass density by adapting the equation of Siri (35) according to the recommendation of Heyward (36). The mid-upper arm circumference (MUAC) of the left arm was measured to the nearest mm with a nonstretch measuring tape. Upper arm muscle area (UAMA) was calculated from the MUAC and tricipital skinfold measurements using the following formula (37): UAMA = [{MUAC (
x tricipital skinfold)}2 / 4
] 6.5. Women who said they were pregnant (n = 94 in April and n = 78 in September) and women with unreliable measurements due to a physical handicap (n = 6 in April and n = 5 in September) were excluded from all analyses using anthropometric measures.
Other information. Socio-demographic, economic, and sanitary information was collected at the level of the household or of the individual. To summarize information, the following 3 indices were computed. 1) The property level index was constructed using a correspondence analysis performed on the matrix of indicator variables that code housing quality (walls, roof, and floor), possessions (electric lamp, petrol lamp, radio, bicycle, or moped), and ownership of cattle. For a given household, the value on the first principal component of the correspondence analysis gives a coordinate that is interpreted as a summary indicator of its economic level. This index was then divided into terciles (38). 2) The hygiene index provided information about hygiene practices and conditions in the household. It was constructed from information concerning the type of water and the distance to the water source, latrines, promiscuity with animals, garbage disposal, and a spot check of the cleanliness of the compound. Based on this index, the sample was divided into 3 classes of hygienic conditions: high, medium, and low. 3) The care for women index assessed the level of attention and support given to women by other members of the household. This index was constructed from the following information: knowledge and use of family planning, obstetrical background (history of stillbirth or infant death), level of prenatal care (number of visits, malaria prophylaxis, and iron supplementation), beneficial practices during pregnancy (improved feeding, alleviation of physical burden, and postpartum rest time), declared ill treatment, and power of decision and autonomy. The index was subsequently divided into terciles.
Data management and analyses. Data entry was performed with EpiData software, version 3.1 (39). Data quality was ensured by quality checks associated with the data entry process, double entry, and also by further data cleaning. Data management, including computation of DDS from the dietary recall and recipe databases, was performed with SAS system, version 9.1 (SAS Institute). The analysis first assessed seasonal variations in the dietary diversity scores, the food consumption, and the nutritional status of women. The DDS, frequency of food group consumption, and the anthropometrics of the women were used as dependent variables and were examined as a function of the "season" variable that was coded for the surveys conducted in April and in September. Next, we identified the effect of socio-demographic and economic factors on DDSs and BMIs at each season. Models with BMI or DDS as the response variable and each economic factor as regressors were thus fitted for each season. Finally, we analyzed the modifying effect (40) of the season on the relation between the mean DDS and the socio-economic variables, the nutritional status and the socio-economic variables, and the nutritional status of women and DDS. For this purpose, an interaction term, season x each variable, was included in the models. The first type error rate for interactions was set at 0.20 to account for the lower power of interaction tests compared with main effects (41). The general linear model was used for quantitative response variables, and the logistic model was used for dichotomous responses. For quantitative variables, unadjusted or adjusted means ± SEM are given. Qualitative variables are expressed as unadjusted or adjusted percentages. All analyses took into account the longitudinal design (repeated measurements on the same women) by including in the model a covariance structure on the errors by means of GEE estimation, except for some special cases (zero percentages) for which analysis was stratified by subject (42). The clustered sample was also taken into account by including a village random effect in the models. Mixed models were fitted with SAS, version 9.1, using the MIXED procedure for quantitative response variables (BMI and DDS) and the GLIMMIX procedure for dichotomous response variables. Except where otherwise specified, the first type error rate was set at 0.05 for all analyses.
| Results |
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30% had a secondary occupation in addition to their agricultural activity. The characteristics of the women who were no longer included in the September sample (n = 67) and those in the initial sample in April did not differ significantly.
Seasonal variations in dietary diversity.
The distribution of the DDS was different between the beginning and the end of the cereal shortage period (Fig. 1). Indeed, by applying the same cut-offs for the terciles of DDS to both seasons, it turned out that, in September, a much lower proportion of women exhibited a low DDS (8.1 vs. 31.6%), and a higher proportion exhibited a high DDS (58.2 vs. 36.2%) than in April, although there were fewer women with a very high DDS (
6 food groups) in September. This resulted in an increase in the mean DDS at the end of the cereal shortage season as compared with the beginning (3.8 ± 1.1 vs. 3.4 ± 1.5 food groups, respectively, P < 0.0001).
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Seasonal variations in nutritional status and associated factors. Between the beginning and the end of the food shortage period the mean weight loss was 1.9 kg (Table 3). The mean BMI fell to <21 kg/m2 and the percentage of underweight women (BMI <18.5 kg/m2) increased from 11 to 17% (P = 0.001). All the skinfold thicknesses decreased between both rounds, which resulted in a decrease in the body fat percentage (23.1% in April vs. 20.3% in September, P < 0.001). In contrast, there was no change in lean mass assessed by the UAMA (36.3 vs. 35.7 cm2, P = 0.1). Very few socio-economic characteristics were associated with these nutritional modifications. Generally, women with higher anthropometric values in April underwent larger decreases. Thus, there was a greater decrease in the mean BMI during the cereal shortage season for literate women (21.7 to 20.5 kg/m2 vs. 20.9 to 20.4 kg/m2 for illiterate women; P for interaction term = 0.09), for women with agricultural incomes (21.1 to 20.4 kg/m2 vs. 20.0 to 20.2 kg/m2; P for interaction term = 0.10), and women who declared illness during the preceding fortnight (20.9 to 20.0 kg/m2 vs. 21.1 to 20.7 kg/m2; P for interaction term = 0.10). Except for these categories, all the women underwent the same seasonal decrease in their BMI.
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| Discussion |
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As expected, seasonal changes in body weight and fat mass were observed among the women in our study. These weight changes were moderate, but not negligible: a mean of 1.9 kg, corresponding to a mean weight loss of 3.5%. Similar seasonal weight changes were reported in women living in other developing countries (4,68,43). The mobilization of body fat stores constitutes a response to a negative energy balance that is caused by low energy intakes combined with heavy agricultural work (4,13). In contrast, we did not observe seasonal change in lean tissue mass, which agrees with the results of other studies (4,44). This would mean that, in years when the food shortage is not exceptional, seasonal stress has no effect on the muscle mass of women, which is probably maintained by the physical demands of agricultural work.
Very few socio-economic factors were found to be associated with the seasonal decrease in the women's nutritional status in our sample, as was the case in other studies (7,9). In our study, only educational levels, morbidity rates, and agricultural incomes of the women were associated with a decrease in their BMI. In fact, it seems that the decreases in BMI were larger in more privileged women because their initial values were also higher. Thus, the relative advantage of some women in April disappeared in September because the cereal-shortage season somewhat levels out the nutritional status. Except for these characteristics, all the other women underwent a similar decrease in their nutritional status during the cereal-shortage period. As for DDSs, the season modified the relation between BMI and the socio-economic characteristics of the women. In April, the BMI was significantly associated with several socio-economic factors, such as the hygienic level of the household, the ethnic group, the level of education, women's agricultural incomes, or the care for women index, but these associations were no longer significant in September (results not shown). On the whole, it appears that the relation between BMI and socio-economic factors was weakened over the period of cereal shortage. As previously discussed, some of the socio-economic characteristics of the women and households may have changed between the 2 seasons. Furthermore, the anthropometric indices decreased between April and September, probably because of dietary factors but also because of an increased workload for women in September. All these changes may have modified the relation between BMI and socio-economic factors.
Finally, we found no significant relation between the DDS and BMI at the end of the cereal-shortage season, whereas we did observe a relation when the DDS was measured before the shortage (28,29). This may be because in September, there was less difference in the DDS and in nutritional status among the women. Gnagna province is a typical Sahelian rural area that is very poor and rather homogenous, and the cereal shortage affects everyone but, as we have shown, without reducing dietary diversity. However, the lack of association of the DDS with the BMI in September may also reflect the limited ability of a simple DDS to represent changes in the energy balance because as it does not take portion size or amount of food into consideration. Global energy intake is likely to be linked to the level of dietary diversity (46), but this assertion may not hold for adults during a cereal-shortage season. Indeed, even if the number of food items increased in September because women made use of a variety of alternative food resources, the consumption of staple foods declines during the seasonal shortage (8,9).
Consequently, DDSs can help identify vulnerable individuals from a socio-economic and nutritional standpoint when measured before the cereal shortage season and are less likely to do so when measured after. In such a context, the usefulness of measuring DDSs at the end of the cereal shortage season is, therefore, questionable, especially when conducted in a yearly or single-round cross-sectional survey. As discussed in the introduction, Swindale et al. (30) recommended, at the household level, measuring the DDS at the end of the food-shortage season to more effectively identify vulnerable households. They also recommended repeating surveys at the same season to avoid seasonal differences when assessing changes over time (for evaluation purposes notably). Our results are in line with their second recommendation, as we have shown that DDSs change across the seasons. However, at least at the individual level and in Sahelian rural contexts, to more accurately target people with the greatest needs, we also recommend measuring the dietary diversity scores before the cereal shortage season, when there are more women with low DDSs.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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5 Abbreviations used: DDS, dietary diversity score, MUAC, mid-upper arm circumference, UAMA, upper arm muscle area; OR, odds ratio. ![]()
Manuscript received 26 April 2006. Initial review completed 10 June 2006. Revision accepted 7 July 2006.
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