« Back

High serum phosphorus levels represent potential risk factor for coronary artery atherosclerosis in young adults, research indicates

Thursday, February 19 2009 | Comments

---

What's This? In healthy young adults, higher serum phosphorus levels--even those that fall within the normal range--are a possible risk factor for coronary artery atherosclerosis, new study data suggest.

Although animal studies and observational studies of patients on dialysis have linked higher serum phosphate levels to vascular disease, the question as to whether phosphate levels in patients with normal kidney function are linked to coronary artery calcium levels has not been studied, the researchers explained.

To investigate this issue, they conducted an analysis of 3,015 healthy young adults (mean age at enrollment, 25.2 yrs) in the prospective Coronary Artery Risk Development in Young Adults study. Phosphorus levels were measured at baseline, and, 15 years later, the presence of coronary artery calcium was evaluated using computed tomography.

The level of coronary artery calcium, which was treated as an ordinal variable, was the primary focus. Calcium levels were divided into 5 categories: no calcification, minimal calcification (1 to <10 units), mild calcification (10 to 100 units), moderate calcification (101 to 300 units), and severe calcification (>300 units).

At the follow-up assessment 15 years after enrollment into the study, 3.2% of the cohort had minimal calcification, 4.8% had mild calcification, 1.1% had moderate calcification, and 0.5% had severe calcification.

In a univariate model, higher phosphorus levels, as a continuous variable, were linked to a lower likelihood of coronary artery calcification (odds ratio [OR], 0.87 per 0.5 mg/dL; P=.0332).

When multivariate analysis was used, however, higher phosphorus levels were associated with a greater likelihood of higher calcium level categories. Specifically, phosphorus values in the highest quartile (>3.9 mg/dL) were associated with more than a 50% increased risk of higher calcium level categories (adjusted OR, 1.52, 95% CI, 1.04-2.22) compared with values in the lowest quartile (<=3.3 mg/dL).

A baseline phosphorus level of >3.9 mg/dL was associated with a greater likelihood of coronary artery calcium measuring >=100 units.

The relationship between baseline phosphorus levels and baseline calcium levels remained similar when the patients with an estimated glomerular filtration rate of <60 mL/min per 1.73 m2 were excluded from the analysis (0.2% of the study population).

"[S]erum phosphorus levels in young adults showed a complex relationship with classic cardiovascular risk factors ...," the authors concluded, noting that the associations between phosphorus and other cardiovascular risk factors "seemed to be qualitatively different from classical cardiovascular risk factors, in the sense that higher phosphorus levels were associated with seemingly protective factors ... and other factors that might be considered to increase cardiovascular risk ...."

"Although phosphorus levels, especially levels >3.9 mg/dL, were associated with coronary artery calcium levels, this association was evident only in multivariate models," they added. (Foley RN, et al. J Am Soc Nephrol 2009;20:397-404.)

Print  |  E-mail