Short-term studies on selected patients have indicated that elevated serum parathyroid hormone (PTH) is an independent risk factor of death. However, long-term data on unselected populations are lacking, thus far. In order to evaluate the predictive value of elevated serum PTH during the last years of life, random persons of age cohorts of 75, 80 and 85 years were followed for 17 years.
A prospective cohort study.
Subjects (n=567) were investigated for calcaemic status including serum intact PTH, serum total calcium (CaT) and ionized calcium (Ca(2+)). Thorough clinical examinations included an assessment of co-morbidity. Mortality data were collected from National Census Records.
Up to 93% of the subjects died within the follow-up. In contrast to Ca(2+) levels, high serum PTH (> or =63 ng/l, IV quartile cut point) was associated with significant over-mortality (HR=1.56, 95% CI: 1.29-1.88) and a 2.3-year reduction of median life expectancy. After controlling for age, gender, co-morbidity and creatinine, the prognostic impact of elevated serum PTH was still significant (HR=1.24, 95% CI: 1.01-1.53). The tendency for over-mortality was consistent in both genders, in all age groups as well as in subjects with varying co-morbidity, renal function, body mass index categories and Ca(2+) levels.
Elevated serum PTH level is an independent predictor of impaired long-term survival prognosis in unselected aged population. Serum Ca(2+) did not emerge as a significant prognostic indicator. The long-term prognostic impact of vitamin D deficiency, the most common cause of elevated PTH levels in the elderly, remains to be investigated.