Document Detail

Choosing an appropriate measure of diarrhoea occurrence: examples from a community-based study in rural Kenya.
MedLine Citation:
PMID:  1634323     Owner:  NLM     Status:  MEDLINE    
Epidemiological studies which aim to identify protective or risk factors for diarrhoea may rely on any of several established measures of disease occurrence, including cumulative incidence, (CI), incidence density (ID), and point prevalence (P); each with its own strengths and limitations. Comparison of these measures was afforded by a community-based study in rural Kenya in which the incidence and prevalence of diarrhoea were measured simultaneously but by independent means in the same group of children. In a cohort study, CI and ID among 138 infants (aged 0-6 months) were 26.1% and 1.41 episodes per 100 infant-weeks, respectively. Among 111 toddlers (aged 18-29 months) CI and ID were 39.6% and 1.96 episodes per 100 toddler-weeks, respectively. In a cross-sectional study of these children, the Ps among infants and toddlers were 9.8 and 6.1%, respectively. Data on incident cases required more time and resources to obtain and evidenced more underreporting of diarrhoea episodes relative to the prevalence data. Other community-based studies have reported the ID of diarrhoea five times more often than any other measure, but appear to have calculated ID incorrectly. The infrequency with which CI and P are reported does not reflect their actual utility.
Researchers conducted a cross sectional analysis (126 infants born in May-June 1986) within a cohort study (138 infants followed between 1984-1986) in the rural Embu District of Kenya to compare the utility, validity, and affordability of various measures of diarrhea occurrence. They were able to follow up on all infants. Cumulative incidence of diarrhea for the 1st 6 months of life stood at 26.1% and for 12 months, 54.9%. The cumulative incidence for the 1st 6 months of followup for toddlers was 39.6%. These toddlers and the infants suffered from an average of 1.96 and 1.41 diarrheal episodes each (incidence density) respectively. Incidence density could then be used to determine the resources needed for treating diarrhea in the community. For example, 1.41 diarrheal episodes among infants/100 infant weeks x 200 infants in a community equals about 2.8 episodes/week. Since the mean duration of each diarrhea episodes in this study was 5.7 days, the needed number of oral rehydration solution packets each week would be 16. The point prevalences of infants and toddlers in the cross sectional analysis were 9.8% and 6.1% respectively. The cross sectional study uncovered 11 more cases than were identified in the cohort study. This suggested more accurate reporting. The point prevalence for infants translated into 13.4 episodes/100 infant weeks which was about 10 times that estimated by the cohort study. This disparity could be due to underreporting of diarrhea in the cohort study and instability in incidence density. Point prevalence could not easily identify risk factors, however. Nevertheless cross sectional studies do produce accurate and useful data more rapidly and inexpensively than do cohort studies. Further few cross sectional and cohort studies have reported cumulative incidence and point prevalence, so it is difficult to estimate their actual utility.
J C Thomas; C G Neumann
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  International journal of epidemiology     Volume:  21     ISSN:  0300-5771     ISO Abbreviation:  Int J Epidemiol     Publication Date:  1992 Jun 
Date Detail:
Created Date:  1992-08-24     Completed Date:  1992-08-24     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7802871     Medline TA:  Int J Epidemiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  589-93     Citation Subset:  IM; J    
University of North Carolina, Department of Epidemiology, Chapel Hill 27599.
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MeSH Terms
Child, Preschool
Cohort Studies
Cross-Sectional Studies
Data Collection
Diarrhea / epidemiology*
Diarrhea, Infantile / epidemiology
Kenya / epidemiology
Rural Health

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