Previous - Next
4.5.1. Mexico
A Mexican study of nutritional supplementation (CHAVEZ and MARTINEZ, 1982) is probably the most critical one for the present considerations. The study was prospective, began before the birth of the child, and longitudinal measures were taken of both activity and development throughout the first 2 years of life.
A cohort of village children were studied in the first year, and in the following year a second cohort were given nutritional supplementation and studied in a similar way. The mothers were supplemented in pregnancy and their children were supplemented throughout early childhood. Time-motion techniques were used, in which foot contacts with the supporting surface were counted to provide an activity rating. The supplemented children showed a higher level of activity from 8 months of age. Their activity increased steadily until they were six times more active than the non-supplemented group by 24 months. The supplemented children had higher DQs on the Gesell Schedules throughout the two years.
This study has frequently been cited as evidence for reduced activity being the mechanism linking undernutrition to poor development. In Figure 3, the activity data have been plotted on the same graph as the Gesell subscale scores of the children. It can be clearly seen that, far from the increased activity leading to improved development, there is little association between the two. The supplemented children's development was better from birth. There were some fluctuations, but the difference showed no sign of increasing. The timing suggests that, if there is a relationship, improved development leads to greater activity. In addition, there are problems with attributing the increased activity to the supplementation alone. The groups were observed a year apart, and there was no control for the increased attention received by the supplemented children.
4.5.2. Colombia
In a nutritional supplementation study in Bogota (SUPER et al., 1981), mothers were supplemented in pregnancy and their children from birth for three years. Observations were carried out when the children were 4 and 8 months of age. In a complex analysis, the results were presented in summary scales. At 4 months, the supplemented children had higher scores on the 'activity scales than the non-supplemented groups. This included 'gross body movements' and 'quiet play' as well as other variables. Children who received both supplementation and stimulation were especially active. There was no effect of supplementation at 8 months of age.
4.5.3. Guatemala
A large supplementation study was conducted in four villages in Guatemala. Pregnant women and children under 7 years were nutritionally supplemented on a self-selection basis. The children's behavior in several games was observed when they were 6 to 8 years old (BARRETT and RADKE-YARROW, 1985). The children who had received the most supplement in the first 4 years of life and when their mothers were pregnant, were compared with those who had received less. The high-supplement group was judged to be more active and exploring than the low-supplement group. However, it is not clear whether some of the supplemented children were still being supplemented. Also, self-selection could be a severe confounder in this study.
The main findings from the review of children with mild-to-moderate undernutrition are:
1. They have low levels of development and school achievement, which are more often related to their height-for-age than their weight-for-height.
2. In a clinical setting, there is evidence from two studies that reduced energy intake results in reduced activity.
3. In free-living children, there is limited evidence of reduced activity in preschool children. Studies have had inappropriate controls or insufficient details have been published to evaluate. In the only study of school children, no reduction of activity was found.
4. Reduced exploration has been found in undernourished children.
5. In three studies of nutritional supplementation, increased activity and exploration have been found. However, in two of them increased stimulation or better home backgrounds could be confounding variables.
6. There is no evidence to support the hypothesis that reduced activity levels lead to poor mental development.
5.1. Developmental levels
5.2. Activity levels
5.3. Relationship between activity and development
5.4. Dietary intakes
5.5. Conclusions
At present, we are conducting a study of stunted children. The main aim is to determine the effects of nutritional supplementation, psychosocial stimulation or both, on growth, development and activity levels. We are also comparing the stunted children with non-stunted children. A house-to-house survey of poor Kingston neighborhoods was carried out, and all children between 9 and 24 months of age had their lengths and weights measured. All those with lengths below -2SD and weights-for-heights below the median of the NCHS standards (HAMILL et al., 1979) were identified (n = 129). The children were randomly assigned to four groups: a stimulated group, a group which received nutritional supplementation, a group which received both treatments, and a control group. Each child of the control group was matched with a non-stunted child (heights above -1SD NCHS, n = 32) who was of similar age and lived nearest. On enrollment, many baseline measurements were taken, including anthropometry, developmental assessments, dietary intakes, social background, index of stimulation in the home, activity levels, and observations of mother and child. We are still analysing the baseline data, some of which we will report here.
On enrollment, all children were given developmental assessments with the Griffiths Test. The stunted groups combined had significantly lower DQs, and their scores were lower on each subscale (Table 4). Their mothers were given the Bettye Caldwell Home Inventory (CALDWELL, 1967), modified for Jamaica, and their standard of housing was assessed. When we controlled for the stimulation in the home, mothers' IQ and height, standard of housing, sex, age and birthweight of the child, the DQs of the stunted and non-stunted groups were still significantly different.
Table 4. Developmental quotients and anthropometry on enrollment by group
Stunted |
Non-stunted |
|||
n = 129 |
n = 32 |
|||
Mean |
SD |
Mean |
SD |
|
DQ |
.2 |
9.0 ++ |
106.3 |
9.9 |
Locomotor |
101.7 |
12.0 ++ |
113.9 |
12.1 |
Hearing & speech |
96.3 |
12.9 ++ |
104.3 |
13.0 |
Hand & eye |
103.7 |
11.4 + |
109.0 |
13.6 |
Performance |
90.8 |
11.7 + |
98.0 |
13.2 |
Height-for-age ° |
-3.0 |
0.7 ++ |
0.1 |
0.6 |
Weight-for-height ° |
-1.0 |
0.7 ++ |
0.0 |
0.8 |
p < .05+
The activity levels of a subsample of the children were observed. Seventy-eight of the stunted and 26 of the non-stunted children, all between 12 and 24 months of age, were studied. Time-motion methods, similar to those of TORUN (1984), were used. In this method, all activities likely to occur are listed, and a check is made every 10 minutes to indicate which ones occurred. The assumption is then made that equal time is spent in each activity which occurs in the period. Torun pointed out that this tends to increase the time apparently spent in the more vigorous activities. We also demonstrated this in the pilot phase. Therefore, we changed the recording interval to one minute, as this more closely approximates the actual timing.
The proportion of time spent in each activity was calculated for the whole observation period. Energy costs of the activities were then taken from values reported by TORUN and VITERI (1989) which were expressed as multiples of BMR. The data were expressed as the proportion of time spent in vigorous, moderate and light or sedentary activities, according to their estimated energy costs. In addition, an activity rating was calculated by multiplying the percent of time spent in each activity by its estimated energy cost and then summing the products. In the pilot phase, 10 children were observed for 3 days. The activity ratings on the 3 days were highly correlated (r = 0.81 to 0.96) and the mean activity ratings were not significantly different on the different days. The children in the main study were observed for 4 waking hours, from 9.30 a.m., for 2 weekdays, never more than 2 weeks apart. Further details of the method and interobserver reliabilities have been reported (MEEKS GARDNER et al., 1990). We also recorded whether certain other activities occurred in the child's environment. Examples of these are whether the child was in a crib or playpen or being held, and whether anyone was talking to or playing with him.
The stunted children spent more time in light activities (p < .001) and less time in moderate (p < .01) and vigorous activities (p < .01) than the non-stunted children (Table 5). The activity rating was significantly lower in the stunted group (mean 1.4, SD .1, p < .01) than in the non-stunted group (mean 1.5, SD .1), and the difference was not due to one group being carried or restrained more than the other. However, in terms of energy cost, the difference was small.
Table 5. Percentage of time spent in activity categories and the activity rating by group
Stunted |
Non-stunted |
|||
n = 79 |
n = 26 |
|||
Activity category |
Mean |
SD |
Mean |
SD |
Light |
78 |
9 ++ |
73 |
7 |
Moderate |
21 |
8 + |
25 |
7 |
Vigorous |
1 |
2 + |
2 |
2 |
Activity rating |
1.4 |
0.1 + |
1.5 |
0.1 |
p < .01+
In the pilot phase, we showed that observing for 4 waking hours gave very similar results to observing for all the waking time from 9.30 a.m. to 5.30 p.m. It is reasonable to assume that these data represent the activity levels of the children for at least this period of time. The amount of time the children slept, while the observers were present, was very similar in the two groups. Further, the mothers were asked how long their child slept the previous day, and again both groups reported very similar amounts (stunted mean 11.9, SD 1.3; non stunted 11.8, SD 1.4). The activity level increased significantly with age (r = .59 p < .001). It was not related to weight-for-height, sex or dietary intake data. The aetiology of the reduced activity in the stunted group was not therefore clearly related to reduced energy availability.
The relationship between the children's activity ratings and development was examined. Separate multiple regression analyses of the activity rating were calculated, using in turn DQs and each subscale quotient as independent variables. In each regression, age was entered first, then the developmental measure followed by group (stunted/non-stunted). The proportions of variance in activity ratings explained by the quotients are shown in Table 6.
Table 6. Percentage of variance in activity ratings explained by age, developmental and subscale quotients, and group
Independent variables |
|||
Quotient used |
Age | Quotient |
Group |
DQ |
34.7 ++ |
6.4 + |
1.3 |
Locomotor |
34.7 ++ |
14.0 ++ |
0.2 |
Hearing & speech |
34.7 ++ |
0.6 |
4.7 ++ |
Hand & eye |
34.7 ++ |
1.0 |
4.6 ++ |
Performance |
34.7 ++ |
2.2 |
3.5 + |
p < .05+
Once age was controlled for, DQ explained a significant proportion of variance (6.4%). The only subscale to explain a significant proportion was locomotor, which explained a larger proportion (14%) than DQ. It would appear that the relationship between development and activity is mostly attributable to locomotor ability. Once age and either DQ or the locomotor quotient were controlled for, there was no difference between the groups in activity.
We cannot determine from these cross-sectional data whether locomotor ability predicts activity or vice versa. However, it would seem likely that locomotor ability in this age range is a potent determinant of activity level. The activity observations were repeated six months later, and when these data will be fully analyzed the relationship should be clearer.
Two 24-hour dietary recalls were obtained from the guardians of the children (WALKER, POWELL and GRANTHAM-McGREGOR 1990). The recalls were taken on weekdays, when the children were well. The total energy and protein intakes were similar in both groups. However, when they were expressed per kilogram body weight, the stunted group actually had significantly higher intakes both in energy and protein than the non-stunted group (Table 7). This finding requires further investigation.
Table 7. Energy and protein intakes upon enrollment
Stunted |
Non-stunted |
||||
(n = 129) |
(n = 62) |
||||
Mean |
SD |
Mean |
SD |
||
Energy |
(kcal/d) |
953 |
448 |
973 |
358 |
(kcal/kg/d) |
113 |
51 ++ |
85 |
31 |
|
Protein |
(g/d) |
26.6 |
17.8 |
29.0 |
14.1 |
(g/kg/d) |
3.1 |
1.9 + |
2.5 |
1.2 |
|
p < 0.005+
A higher rate of morbidity in the stunted group may explain some of this difference, but is unlikely to explain it all.
It is unwise to draw firm conclusions before all the analyses are completed. The stunted children had markedly lower DQs than the non-stunted group, even at this young age. They were also less active, but did not have lower energy intakes per kilogram body weight. Therefore the reduced activity was not clearly related to reduced available energy.
The children's development was related to their activity rating mostly through their locomotor development. When their age and locomotor quotient were controlled for, the groups did not differ in activity ratings.
The Jamaican studies referred to in this paper were funded by the Ford Foundation U.S.A., Population Council and United Nations University. We thank S. Chang for assistance in the preparation of this paper.