4. Adult BMI and morbidity

When BMI was analysed according to whether or not the adults smoked, the expected relationship was found. Cigarette smokers had a higher probability of being thinner than non-smokers. For pipe and cigar smokers the sample size was too small to reach any conclusion. Both male and female cigarette smokers are thinner than non-smokers.

The PNSN survey also provides the opportunity of linking the BMI of individuals with their morbidity assessed in a variety of ways. Figure 6 shows the relationship in adults between their BMI and the number of days spent in bed during the 2 weeks before the survey. There is a U-shaped curve in morbidity similar to that often published of the mortality curve of BMI in Western societies. This means that thin as well as obese people have a greater probability of staying in bed than normal individuals.

It is noteworthy that there is a modest increase in morbidity for the 16.0-17.5 BMI category but the second category of 16.0-17.0 shows a marked increase in morbidity. When each condition leading to their morbidity was assessed it was assumed that febrile episodes and diarrhoeal disease would feature prominently in the causes of the morbidity because these are the two prominent features in malnourished children. In practice, neither fever nor diarrhoeal disease contributed to their morbidity but upper respiratory tract infections were common.