to produce change at an individual level, a community level, or both. All aspects of each broad determinant of health are not equally amenable to intervention, however. For example, the social environment of isolated senior citizens can be improved by increasing contact with others, but their genetic makeup is not amenable to change.

Time frames for measuring health changes vary widely, from days to decades. Some successful interventions will produce observable results within a year or two, but others may be followed by long latency periods before significant changes in health status can be observed. The impact of an intervention may also be influenced by when it reaches an individual because, as noted above, there appear to be "critical periods" in human development. Certain interventions in childhood may have long-delayed yet long-lasting results. In addition, the population effects of interventions are also important to consider. Small changes at the individual level may have important ramifications when applied to a whole community (Rose, 1992).

The traditional targets for intervention have been specific diseases or behaviors, and categorical funding streams for both research and the delivery of services encourage this approach. The field model of the determinants of health encourages consideration of a wider array of targets. For example, if adolescents' sense of well-being can be improved by reducing their feelings of alienation and hopelessness, can unintended pregnancies, alcohol and other drug use, crime, and the school dropout rate all be reduced? A multidimensional approach would be required, focusing on education, social and community involvement, family preservation, and improved social networks for teens and their parents. Community-level interventions might include after-school programs, athletics (e.g., midnight basketball), and church-based programs.

Whether focused on individuals or the community as a whole, health improvement efforts should be targeted at specific causal pathways or should employ interventions that have been proven effective. There is an obvious tension between what is now known and what we need to know to improve health. For example, the biologic pathways through which poverty or low social class influence health have not been adequately elucidated. A tension also exists between what is now measurable with valid and reliable indicators and what is not measurable, but may be important.

The multidimensional approach may be unfamiliar to health professionals because it is new and relies on partnerships with



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