Neighbourhood, family and health care.

OBJECTIVE The effects of family and place on health outcomes may be seriously misestimated by standard analytic techniques. The information-rich settings in several Canadian provinces can provide appropriate designs to minimize biases resulting from omitted variables and measurement error. This paper compares siblings with children living in the same neighbourhood (but not in the same family) in terms of health care utilization and health care costs. A complete history of residential mobility since birth permits an estimate of the effects of exposure to different environments. METHODS Registry data from a Manitoba cohort born between 1978 and 1985 and continuously resident in the province generated a large sample of same-sex siblings and neighbours (N = 18,280). Administrative information on physician billings, hospital inpatient stays, and costs provided data on utilization between ages 12 and 17. RESULTS Large effects on the outcome variables were associated with being in the same family (correlations up to 0.50), whereas the correlations representing upper limits on neighbourhood effects were usually small. These neighbourhood correlations typically shrank slightly after adjustment for family effects. Higher neighbour correlations with utilization (particularly ambulatory visits) occurred in rural Manitoba and probably reflect variation in access to care. Higher correlations are associated with relatively small neighbourhoods and with families remaining in the neighbourhood for at least 17 years. DISCUSSION Although specific variables taken from administrative data are only marginally predictive, our results emphasize the importance of "family" in affecting health care utilization in Manitoba. The minimal effects of neighbourhood differ from those found by investigators generally using weaker designs and emphasizing the significance of neighbourhood.