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Case-control study of risk of dehydrating diarrhoea in infants in vulnerable period after full weaning

BMJ 1996; 313 doi: (Published 17 August 1996) Cite this as: BMJ 1996;313:391
  1. Sandra Costa Fuchs, associate professora,
  2. Cesar Gomes Victora, professorb,
  3. Jose Martines, medical officerc
  1. a Department of Social Medicine, School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, R Ramiro Barcelos 2600, sala 415, CEP 90035-003, Porto Alegre, RS, Brazil
  2. b Mestrado de Epidemiologia, School of Medicine, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
  3. c Diarrhoeal Diseases Control Programme, Word Health Organisation, Geneva, Switzerland
  1. Correspondence to: Dr Fuchs.
  • Accepted 11 June 1996


Objectives: To investigate risk factors for dehydrating diarrhoea in infants, with special interest in the weaning period.

Design: Case-control study.

Setting: Metropolitan area of Porto Alegre, Brazil.

Subjects: Cases were 192 children aged 0-23 months hospitalised with acute diarrhoea and moderate to severe dehydration. Controls were 192 children matched for age and neighbourhood who did not have diarrhoea in the previous week.

Main outcome measures: Associations between dehydrating diarrhoea and child's age, type of milk consumed, time since breast feeding stopped, and breast feeding status.

Results: In infants aged <12 months the risk of dehydrating diarrhoea was significantly higher in the first 9 months of life (P<0.001), and in those aged 12-23 months the risk was again greater in younger children (12-17 months) (P = 0.03). The type of milk consumed before start of diarrhoea episode was strongly associated with dehydration independent of socioeconomic, environmental, maternal reproductive, demographic, and health services factors. Compared with infants exclusively breast fed, bottle fed infants were at higher risk (odds ratio (95% confidence interval) for cow's milk 6.0 (1.8 to 19.8), for formula milk 6.9 (1.4 to 33.3)). Compared with those still breast feeding, children who stopped in the previous two months were more likely to develop dehydrating diarrhoea (odds ratio 8.4 (2.4 to 29.6)). This risk decreased with time since breast feeding stopped.

Conclusion: These results confirm the protective effect of breast feeding and suggest there is a vulnerable period soon after breast feeding is stopped, which may be of relevance for developing preventive strategies.

Key messages

  • In this study infants who were exclusively breast fed were six times less likely to have dehydrating diarrhoea than bottle fed infants

  • Partially breast fed infants were at intermediate levels of risk

  • Children who were recently weaned showed a higher risk of dehydrating diarrhoea than those who had been weaned for six months or more

  • Recently weaned children presenting with diarrhoea should receive closer attention from health workers


  • Funding World Health Organisation.

  • Conflict of interest None.

  • Accepted 11 June 1996
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