The study by Tobe and colleagues1 is a cross-sectional evaluation of the relationship between ambulatory blood pressure (BP), job strain, and marital cohesion in a large sample of middle-aged men and women. It has previously been reported by many groups that work stress, operationalized as high demands coupled with low control or decision latitude, is related to BP.2 Earlier work from this research group has shown that low marital cohesion is inversely associated with ambulatory diastolic pressure in mild hypertensives.3 The hypothesis was tested in the present study that martial quality and job stress factors interact in their association with BP.
The results are interesting in extending the study of psychosocial correlates of cardiovascular risk from single to multiple interacting factors. At present, much research in this field evaluates factors such as work stress, social support, or marital strain in isolation. However, interactions are important, as favorable social relationships may offset the adverse effects of other stressful exposures. Having said this, there are features of the study that limit the conclusions that can be drawn.
The first concerns the study population. The study attracted a preponderance of high status, high income participants, many of whom worked in an academic health setting, and who were much more physically active than typical Canadian adults. Not only does this impinge on the generalizability of results, it may also have undermined the influence of marital cohesion. Poor marital relationships have greater adverse effects in the presence of financial strain and material deprivation, when the (often conflicting) choices about use of money in nonharmonious couples become critical. Job strain is also socially graded, with lower levels in higher status occupations in which demands are balanced by greater autonomy and opportunities for skill development. It is possible, therefore, that the impact of the interaction between job and marital strain would have been greater in a more diverse study population.
Second, the critical interaction between high job and marital strain is not illustrated, and its precise nature is unclear. The interaction term was significant in the regression on 24-h systolic BP, independently of factors such as age, gender, and body mass. The effect is said to be due to high marital cohesion being related to lower BP in participants reporting high job strain, but it could equally be significant because high marital cohesion is related to elevated BP in low job strain participants. There is no very convincing explanation of why associations were previously found between marital cohesion and diastolic pressure,3 whereas in this study effects were only significant for systolic pressure.
Third, it cannot be assumed from a cross-sectional study that “double exposure” is a determinant of ambulatory BP. This report is evidently from the baseline phase of a longitudinal investigation. It will be interesting to discover whether changes in job or marital stress modify ambulatory BP, as has recently been reported for changes in financial strain.4