Cancer incidence in hypertensives.

Cancer incidence was measured over a 5-year period (1978 to 1982) in 4067 hypertensive patients, and 10,366 normotensive patients from general practices in southwestern Ontario. For cancer of all sites an elevated incidence was found among hypertensive patients. The elevation was most pronounced among newly diagnosed hypertensive patients, with hypertension of moderate or greater severity, and for sites that have been described in clinical reports as being capable of producing a rise in blood pressure. It is tentatively concluded that the causal direction is from cancer to hypertension, rather than the reverse. If this conclusion is correct, the associations that have been reported between cancer mortality and hypertension may be due to an effect of blood pressure upon survival from cancer.