Health-related mobility, health inequalities and gradient constraint. Discussion and results from a Norwegian study.

BACKGROUND: Recent studies have argued that health-related mobility does not widen social class health differentials, but rather moderates them. This is termed gradient constraint. This paper examines gradient constraint from a theoretical and empirical angle.
METHODS: How health-related mobility influences social class health differentials is discussed using hypothetical models. In a Norwegian survey with data on intergenerational mobility (N = 1,853 males aged 30-69 years), mean health and height values for different subsections of the sample were analysed.
RESULTS: When initial social class health differences are large and mobility widespread, health-related mobility may lead to smaller differentials, but the result depends on how closely mobility varies with health. This empirical study found non-significant increases in height and health differentials from class of origin to class of destination. The interpretation has to consider effects of both social mobility and social causation. Health is measured in the post-mobility situation and the effects of social mobility and social causation are difficult to separate from each other for most of the health indicators analysed. However, this limitation does not apply to height which is not influenced by social causation during adulthood. In these data mobility did not reduce the height differential.
CONCLUSION: Health-related mobility can either lead to smaller or larger social class health differentials. The specific effects of social mobility cannot be determined without knowing how social causation has interfered. The intergenerational mobility process analysed in this paper does not show gradient constraint as regards the height differential between the worker and higher occupational categories.