|The Functional Significance of Low Body Mass Index (IDECG, 1992, 203 p.)|
|Assessing the linkages between low body mass index and morbidity in adults: evidence from four developing countries|
Durnin: How did you estimate the income of the females?
Kennedy: We had data on sources of income within the household for off-farm income. For farm income we had information on who controls the plots, crop production and distribution, whether it was marketed or for home consumption and if it was for home consumption it was valued at what they would have to pay in the open market.
Durnin: In the Philippines, males were ill for 7 days out of 14. Is that representative of that population?
Kennedy: Yes, there was a lot of malaria. Increased income improved energy consumption and anthropometry but did not change the morbidity patterns of children or adults. It is probably because it is such a squalid environment with so much disease about that the extra money for food does not make up for this.
Naidu: With such high morbidity, poor environments, and lack of distinction between kinds of severity of illness, do you think any relationship with BMI is being masked?
Kennedy: The methodological problems are indeed great and this self-reporting method is not ideal. The 2 week period of recall is too long: 1 week would be better. The reported numbers are high but we know there is underreporting of illness.
Ferro-Luzzi: I would like to ask Eileen Kennedy, are there any more data on LSMS World Bank on Ghana or from elsewhere to use to address the issue of mortality and disease?
Kennedy: Yes, there is a series of LSMS studies that are nationwide representative samples. But their method for collecting morbidity was a 4-week recall and validation studies suggest that recall beyond 1 week is unreliable; it underestimates illness and people only remember their most severe disease.
Scrimshaw: The period of recall is situation specific. In Guatemala where the same worker went to the same family every 2 weeks for 3 years, we did get useful data from a 2-week recall. In another situation, validation of 2-week recall showed underestimation, and picked up only severe illness. If you have a large enough sample, a point prevalence, in which you combine the self-reporting of the individual, with probing and direct observation, can be useful for that period only.
Waterlow: In many countries most children seem to be ill about 15-20% of the time. If you do a 1-day point prevalence, out of every 100 children you would get 15 ill, and that is a good number. In many situations you could easily visit 200 children a day, and from a practical point of view it seems little work, so I like the idea of point prevalence.
Ferro-Luzzi: A point prevalence for recognized disease is OK but it would be difficult for nonspecific disease, not easily identified.
Scrimshaw: There are problems with point prevalence because of fluctuating levels of endemicity and hyperendemicity with superimposed epidemicity and seasonal fluctuations with diarrhoea, respiratory disease etc. and, of course, no field method will pick up unsymptomatic disease like HIV. With frequent rectal swabs and a good laboratory you could pick up very high levels of non-symptomatic disease.
Waterlow: I don't think we can expect to diagnose diseases like HIV, tuberculosis, malaria, but we can record symptoms and that is useful.
Allen: There is a case for detecting illnesses such as malaria that are clearly caused by environmental pathogens.