Relationship between Lung Function and Hypertension among Rural Canadians using Fractional Polynomials

Studies have shown that persons with lower pulmonary function have a higher risk for developing cardiovascular diseases including hypertension. The objectives of this paper are to examine: (i) the relationship between lung function and hypertension; and (ii) the correct functional forms of the continuous predictors of hypertension using fractional polynomials.

This analysis was based on data from a cross-sectional community study of 1,834 adult subjects aged 18-79 years conducted in 2003 in Humboldt, Saskatchewan, Canada. Clinical measurements were made during a clinic visit, and other information was collected from a questionnaire. Logistic regression analysis was conducted to determine associations between hypertension and lung function measurements. Multivariate fractional polynomial logistic regression model was used to preserve the continuous nature of the predictor variables.

There was an expected significant difference between men and women in values for FVC and FEV₁. We observed that the ordinary logistic regression model and fractional polynomial model gave the same functional form when stratified by gender. The data suggest an increasing risk of hypertension with decreasing FVC and FEV₁ values. After adjusting for potential risk factors including age, body mass index, parental history of hypertension and smoking, there was increased risk of hypertension among women with low FVC [OR_adj: 0.73 (95% CI: 0.56, 0.95)]. We did not see this association for men [OR_adj: 1.10 (95% CI: 0.90, 1.33)]. We observed that the risk of hypertension increases with decreasing FVC for women after adjusting for potential risk factors.

DOI: http://dx.doi.org/10.4038/sljastats.v12i0.4967

Sri Lankan Journal of Applied Statistics Vol.12 2011 pp.41-61