Bone Mineral Density Linked to Pulmonary Function and Is Influenced by Age, Race

Pulmonary function (PF) is positively associated with bone mineral density (BMD) in US adults, and the association is influenced by race and age, according to study findings published in Osteoporosis International.

As many as 60% of patients with chronic obstructive pulmonary disease have osteoporosis and as many as 72% have osteopenia. Investigators aimed to determine whether a correlation exists between BMD and PF as measured by forced expiratory volume in 1 second (FEV₁) percent predicted and the ratio of FEV₁ to forced vital capacity (FVC).

The researchers conducted a cross-sectional study based on data from 6327 adults (mean [SD] age 44.51 [15.64] years) in the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2010 to evaluate the association between PF and BMD. Multiple linear regression models, adjusted for a range of confounders, analyzed the relationship between FEV₁ percent predicted (independent variable), FEV₁/FVC (independent variable) and BMD (dependent variable). In measuring BMD, the investigators used dual-energy X-ray absorptiometry to measure BMD of the total femur, femur neck, total spine, and first lumbar vertebrae (L1).

Participants (45% women; 45% non-Hispanic White, 20% Mexican American, 19% non-Hispanic Black, 12% other Hispanic) were divided into quartiles based on their FEV₁ percent predicted. Participants in the highest quartile were more likely to be younger, White/non-Hispanic, and male, to have lower serum uric acid, total protein, and body mass index, and to have higher cholesterol and serum vitamin D.

Investigators then determined the overall relationship between FEV₁ percent predicted and BMD, then adjusted the model to analyze for age and race, then performed an additional fully adjusted analysis that took into account numerous variables including age, race/ethnicity, height, drinking behavior, body mass index

(BMI), total protein, serum calcium, serum uric acid, cholesterol, serum phosphorus, and blood urea nitrogen.

Overall, investigators found a positive association between FEV₁ percent predicted and femur BMD that was more significant in those aged 20 to 34 years and those aged 50 years and older, and in individuals who were White/non-Hispanic.  A positive correlation was also found between spinal BMD and FEV₁/FVC (β = 0.275; 95% CI, 0.102-0.448; P =.002), although correlations between FEV₁/FVC and the other BMD categories were much weaker.

In the fully adjusted model, FEV₁ was positively correlated with femur BMD (β, 0.032; 95% CI, 0.010-0.054; P =.004) and had approximately similar strength correlations with total spine, femoral neck, and L1 BMD. A positive correlation was seen between FEV₁/FVC with spine BMD (β, 0.275; 95% CI, 0.102-0.448; P =.002), although correlations between FEV₁/FVC and the other BMD categories were much weaker.

The positive association between FEV₁ percent predicted and femoral BMD stratified by sex, race, and age remained significant in White non-Hispanic participants (β, 0.054; 95% CI, 0.022-0.085; P <.001), those aged 20 to 34 years (β, 0.074; 95% CI, 0.027-0.121; P =.002), and those at least 50 years of age (β, 0.033; 95% CI, 0.001-0.064; P =.041). Gender was not a correcting factor for the positive correlation between FEV₁ percent predicted and BMD.

Study limitations include the nature of cross-sectional design, which does not allow confirmation of causality; insufficient data; incomplete results; and unaccounted-for confounders of dietary habits, occupation, daily smoking, exercise, estrogen levels, and thoracic spine fractures. The study authors concluded that “The PF of the American population is positively correlated with BMD, and mixed factors such as race and age may affect this relationship.” As the investigators further noted, “We found a positive association between FEV1(% predicted) and femur BMD in the US population… more significant in individuals aged 20–34 years, those aged 50 years and older, and non-Hispanic whites.”

This article originally appeared on Pulmonology Advisor