This paper uses longitudinal household data from the Kagera Region of Tanzania collected in 1991-94 to measure the impact of mortality of prime-aged adult household members on the level and changes in physical well-being of the elderly. Our measure of physical wellbeing is the body mass index (BMI), defined as the respondent's weight in kilograms divided by height in meters squared. BMI is considered a strong measure of overall health status for adults as it is predictive of morbidity and mortality and responds to shorter-term changes in energy inputs and outputs. In industrialized countries, extreme low and high values of BMI have been associated with higher risk of morbidity and adult mortality (Duerksen et al 2000, Engelman et al 1999, Expert Subcommittee 1998, Kushner 1993, Stefanovic et al 2000, Waaler 1984). Adults with a BMI greater than 35 double their mortality risk and run even higher risks of morbidity from cardiovascular disease, diabetes and certain cancers (Kushner 1993). The mortality risk of low BMI in industrialized countries is confounded by smoking behavior, as there tends to be a positive correlation between leanness and smoking and those who smoke also suffer from smoking-related causes of morbidity and mortality. Mortality associated with low BMI is due to tuberculosis, lung disease, and lung and stomach cancer (Expert Subcommittee 1998). There are very few studies of health risks for the BMI of adults or the elderly in developing countries, where the highest risks of morbidity and mortality in adults are associated with extremely _low_ values of BMI, indicative of acute under-nutrition (WHO Expert Committee 1995). In a longitudinal study of Chinese 70 and older, those with lower BMI had higher mortality, after controlling for age, sex and physical activity (Woo et al 1998). In a study of poor men in Calcutta, those with BMI less than 16 were more likely to have respiratory tract infections and tuberculosis (Campbell and Ulijaszek 1994). The relation between BMI and infection runs in both directions: morbidity contributes to changes in BMI and low or high BMI raises the susceptibility to ill health (Expert Subcommittee 1998).

Aging affects both stature and weight, which can confound the interpretation of BMI levels and health risk at older ages (Expert Subcommittee 1998). Height declines by 1-2 cm/decade due to compression and other changes in the vertebra, reduced muscle tone and worse posture. In western countries, weight plateaus after age 65 in men and 75 in women due to reduced cell mass and loss of body water. However, in the short run, changes in weight and BMI are predictive of greater health risk. Thus, the recommended "healthy" range for BMI among adults varies according to the source and sometimes by age and gender, but in general the range for the elderly is higher than for middle-aged adults (Kushner 1993). For example, the U.S. Department of Health and Human Services recommends a BMI range of 19-25 for those aged 19-34 but a range of 21-27 for those 35 and older. The U.S. National Academy of Sciences suggests a range of 23-28 for those 55-64 and 24-29 for those 65 and older, compared to a range of 20-25 for those aged 25-34 (Kushner 1993).

In this paper we analyze the impact of prime-aged adult mortality and other determinants of nutritional status on the level and changes in BMI of the elderly in Northwestern Tanzania. The elderly are defined as everyone over 50, to distinguish between those in the prime-aged _2_