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TABLE 6 Coverage in the follow-up cohorts by migration status

Village type

Migrants

Nonmigrants


T

P

%

T

P

%

Fresco╣

Santo Domingo

212

79

37.3

382

332

86.9

Espiritu Santo

138

66

47.8

285

256

89.8

Atole▓

Conacaste

201

80

39.8

474

408

86.1

San Juan

176

71

40.3

301

282

93.7

Supplemented Combined

727

296

40.7

1442

1278

88.6

Comparison

Subinal

61

28

45.9

177

137

77.4

Las Ovejas

98

44

44.9

288

236

81.9

El Caulote

76

33

43.4

229

168

73.4

Comparison Combined

235

105

44.7

694

541

78.0

ALL VILLAGES

962

401

41.7

2136

1819

85.2

╣ Large Fresco village, Santo Domingo; small Fresco village, Espiritu Santo.
▓ Large Atole village, Conacaste; small Atole village, San Juan; T. target sample; P. participants; %, coverage.

Table 6 presents coverage rates by migration status. Coverage rates differed between supplemented and comparison villages; among nonmigrant subjects, coverage rates were ~10% greater in supplemented (88.6%) than in comparison villages (78.0%.). This is probably the result of the good rapport built by INCAP during the 9 y of the longitudinal study. On the other hand, coverage for migrants was slightly less in supplemented (40.7%) than comparison villages (44.7%). This may be due to differences in how the target sample was defined in supplemented and comparison villages. The target sample of migrants in the comparison villages was identified using information available in the 1987 census. Therefore, only adolescent migrants whose families were still living in the villages at the time of the follow-up census were selected. In contrast, in the supplemented villages, follow-up cohorts whose entire families had migrated before the beginning of the follow-up study also were selected, using records from the longitudinal study. Some of these migrant families were located using information provided by neighbors and relatives; however, as a result of the absence of parents or close relatives, follow-up cohorts belonging to these families were much more difficult to locate than migrants whose families were still living in the villages.

Coverage rates for migrants were overall much lower than those for nonmigrants because of the difficulty of locating migrants and because data collection in migrants was restricted to those living in Guatemala City and two provincial cities. The decision to focus on these locations was based on resource restrictions and the fact that information available at the beginning of the study indicated that ~64% of the subjects for whom locations were known lived in one of these three cities. Coverage for migrants known to have moved to these three cities was 62%. For the entire migrant sample, coverage was 42% (Table 6).

Coverage rates for females were greater in both migrants and nonmigrants. In migrants, coverage rates were 45.6% and 36.9% for females and males respectively; these patterns were similar in supplemented (females: 176/394 = 44.75% and males: 120/333 = 36.0%) and comparison villages (females: 65/134 = 48.5% and males: 40/101 = 39.6%). In nonmigrants, coverage for females was 89.7% and for males 81.2%. Coverage rates were greater in females in supplemented villages (females: 623/666 = 93.5% and males: 655/776 = 84.4%) as well as in comparison villages (females:278/339=82.0% and males:263/255=74.1%).

TABLE 7 Percent coverage in the follow-up exhorts by birth cohorts and gender

Cohorts╣ Village type

Females

Males

I

II

III

IV

I

II

III

IV

Fresco▓

Santo Domingo

84.1

73.0

56.4

68.8

82.3

70.9

61.5

50.0

Espíritu Santo

90.4

74.4

65.9

69.2

87.5

77.3

55.8

62.1

Atole│

Conacaste

84.8

74.1

79.4

81.4

87.5

65.7

55.8

53.8

San Juan

76.3

79.0

67.9

67.9

90.8

74.0

58.5

57.1

Supplemented Combined

83.8

75.1

67.9

73.1

87.1

71.2

60.3

54.5

Comparison

Subinal

89.2

83.3

54.2

58.3

90.9

67.4

46.7

42.9

Las Ovejas

83.8

81.2

64.7

66.0

85.7

81.4

61.9

49.0

El Caulote

87.8

76.6

55.2

47.6

91.7

70.6

38.5

42.4

Comparison Combined

87.0

80.4

58.6

57.5

88.8

73.7

51.8

45.5

ALL VILLAGES

84.8

76.6

65.2

67.5

87.6

71.9

57.9

51.2

╣ See Table 3 for cohort definitions. Values are percentages.
▓ Large Fresco village, Santo Domingo; small Fresco village, Espíritu Santo.
│ Large Atole village, Conacaste; small Atole village, San Juan.

Subjects were classified into four birth cohorts according to ages of exposure to supplementation (Table 3). Table 7 presents coverage rates by cohort and village. In general, Cohort I has the highest coverage rates, followed by Cohort II and finally by Cohorts III and IV. Younger subjects may have had more time to participate in the various tests and interviews than older subjects.

Table 8 presents coverage rates for the different study domains by village type. Coverage rates were ~ 70% for most domains. The low coverage for blood collection deserves comment. Interviews of subjects who had refused to participate and of their families revealed that anxiety related to blood collection was one of the principal reasons for nonparticipation. Some subjects felt that the very small amount of blood collected (5 mL) was very large relative to the total blood volume in an adult. In one village, there were rumors that the blood was being sold. To remedy the situation, subjects were informed that blood collection was not essential for participation in the rest of the tests, measurements and interviews. In addition, subjects were reminded that blood samples also were used for the diagnosis of anemia, with treatment provided when necessary. Subsequently the refusal rate declined, though refusals to provide a blood sample among participants in the study remained high.

Table 8 also presents coverage rates for the different study domains in the comparison villages. Coverage rates were slightly less than found in the supplemented villages, but follow the same patterns. For the work capacity test, more subjects than originally planned were examined in comparison villages (see Haas et al. 1995).

Coverage rates for anthropometric measurements of parents of the follow-up sample was 82.4%, with no difference between supplemented (809/979 = 82.6%) and comparison villages (386/472 = 81.8%). Similar coverage rates were obtained for the life history of mothers of the follow-up samples (82.7%), with similar coverage rates for supplemented (452/543 = 83.2%) and comparison villages (207/253 = 81.8%). In contrast, coverage of the income and wealth questionnaire applied to heads of households was lower (62.0%), with rates being similar in supplemented (62.5%) and comparison villages (60.7%). The low coverage rates for the income and wealth interviews were due in part to the long time required to obtain the information and the fact that most of the heads of households worked in agriculture and were away during most of the day.

TABLE 8 Coverage rates by study domain and village type for the follow-up cohorts

Study area

 

Supplemented villages

Comparison villages

T

P

%

T

P

%

Anthropometry

2169

1554

71.7

929

633

68.1

Medical Exam

2169

1543

71.1

929

630

67.8

Hand-wrist x-rays

1149

920

80.1

459

337

73.4

Blood sample

2169

1196

55.1

929

425

45.7

Psychology tests Functional competence and intelligence

1897

1367

72.1

766

532

69.5

Information processing

1897

1331

70.2

766

521

68.0

Life history

Males

1109

742

66.9

456

282

61.8

Females

1060

730

68.9

473

311

65.8

Work capacity subsample

388

361

93.0

152

178

100.0╣

T. target sample; P. participants, %, coverage.
╣ More subjects were examined than originally planned.

Concluding remarks

Full details about design and methods, such as contained in this article, are often not readily available in the literature. The INCAP longitudinal and follow-up studies are among the most important sources of information from developing countries about child growth, development and nutrition and it is likely that there will be continued analyses of these data for years to come. It is important to have a faithful record of the design, objectives, methods and procedures, particularly for the benefit of analysts who may not have been directly involved with the studies.


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