Randomised studies of income supplementation: a lost opportunity to assesshealth outcomes

Background-Despite the wealth of evidence linking low income to ill health, there is little information from randomised studies on how much and how qu ickly these risks can be reversed by improvements in income. Objective-To conduct a systematic review of randomised studies of income su pplementation, with particular reference to health outcomes. Design-Extensive searches of electronic databases and contact with previous authors. As well as searching for trials that were specifically designed t o assess the effects of increased income, studies of winners and losers of lotteries were also sought: if winning is purely chance, such studies are, in effect, randomised trials of increased income. Results-Ten relevant studies were identified, all conducted in North Americ a, mostly in the late 1960s and 1970s. Five trials were designed to assess the effects of income supplementation on workforce participation and random ised a total of 10 000 families to 3-5 years of various combinations of min imum income guarantees and reduced tax rates. Two trials were designed to a ssess re-offending rates in recently released prisoners and randomised a to tal of 2400 people to 3-6 months of benefits. One trial was designed to ass ess housing allowances and randomised 3500 families to three years of incom e supplements. One trial assessed the health effects of 12 months of income supplementation in 54 people with severe mental illness. Finally, one stud y compared three groups of people who won different amounts of money in a s tate lottery. In all these studies the interventions resulted in increases in income of at least one fifth. However, no reliable analyses of health ou tcome: data are available. Conclusions-Extensive opportunities to reliably assess the effects of incre ases in income on health outcomes have been missed. Such evidence might hav e increased the consideration of potential health effects during deliberati ons about policies that have major implications for income, such as taxatio n rates, benefit policies, and minim sm wage levels. Randomised evidence co uld still be obtained with innovative new studies, such as trials of full b enefit uptake or prospective studies of lottery winners in which different sized winnings are paid in monthly instalments over many years.