H E A LT H A N D S O C I O E C O N O M I C S TAT U S
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Demonstrating that iron deficiency impedes maximal capacity and endurance does not reveal the economic consequences of iron deficiency in daily life. Those consequences may be more closely aligned with energy efficiency—the amount of physiological energy required to perform a given task. In fact, evidence from randomized treatment-control studies of Chinese female cotton mill workers and Sri Lankan female tea plantation workers suggest that elevated productivity resulted in changes in time allocation. Specifically, neither study found evidence of greater productivity per hour among iron-deficient subjects who received iron supplements relative to subjects who were not supplemented, but in both cases, treated women reallocated time away from work and toward nonwork activities (Edgerton et al. 1979; Li et al. 1994). Results from a random assignment treatment-control iron supplementation study of male rubber workers, however, indicates that treated individuals who were anemic at the initiation of the study were able to tap about 20 percent more rubber after supplementation, compared with anemic controls (Basta et al. 1979). Interpretation of this result is complicated by the fact that attrition from the study exceeded 50 percent; if those subjects who did not benefit from the study were more likely to attrit, the estimated benefits would be biased upward. The Work and Iron Status Evaluation (WISE) is designed to examine the immediate and longer-term impact of providing iron supplements to older adults in Central Java, Indonesia (Thomas et al. 2006). In this population, about one-quarter of older men and one-third of older women are iron deficient, as indicated by low hemoglobin. Older males are randomly assigned to receive a weekly iron supplement, or an identical-appearing placebo, for slightly more than a year. Everyone in the man’s household is similarly assigned to treatment or control. (In the small fraction of households with more than one older male, a random male is selected to determine assignment to treatment or control for the entire household.) Respondents who were iron deficient prior to the intervention and who were assigned to the treatment have higher levels of iron in their blood and are able to cycle longer on an ergocycle at the end of the intervention, relative to comparable control subjects. Relative to similar controls, treated subjects are more likely to be working, lose less work time to illness, are more energetic, are better able to conduct physically arduous activities, and enjoy better psychosocial health. About half the male workers in the study are self-employed (primarily as rice farmers), and the other half are paid a time wage. There is no evidence that hours of work were affected by the treatment, for either time-wage workers or the selfemployed. Among males who earned a time wage, there is no evidence of changes in productivity as indicated by hourly earnings. Of course, if their wages are set by an employer, it is not obvious that the worker will reap the benefits of greater productivity. This is not true for the self-employed; males who were iron deficient and selfemployed at baseline reported 20 percent higher hourly earnings after six months of supplementation relative to similar controls. Since there was no change in their hours of work, this translates into 20 percent higher income from labor. Wage workers who received the treatment reduced their amount of time spent sleeping by about 40 minutes per day and reallocated this time to leisure. Selfemployed workers made no such adjustments. A picture emerges of iron deficiency