Plasma albumin and calcium concentrations, and long-term mortality in primary health care patients in Sweden

Abstract

Objective Low plasma (p)-albumin and p-calcium concentrations are associated with increased mortality in hospitalised patients. There are few studies addressing this in primary care. Low p-calcium has been associated with mortality, but it is not known whether this applies to p-albumin. Could p-albumin and p-calcium be used as markers of an increased risk of mortality? Purpose To study p-albumin and p-calcium at baseline and their association with mortality after 10–14 years. Design Prospective cohort study using data from a large primary health care area and the National Swedish Cause of Death Register. Setting Primary health care in Skaraborg, Sweden. Subjects 43,052 patients (39.1% men), ≥18 years, 60.7 ± 18.4 years with p-albumin and p-calcium concentrations registered in 2001–2005. Main outcome measures P-albumin and p-calcium concentrations at baseline and their association with mortality after a mean follow-up period of 10.3 ± 4.0 years. Results Low p-albumin was associated with total mortality compared with normal p-albumin, greatest at lower ages (18–47 years). The hazard ratios for women and men were 3.12 (95% CI 1.27–7.70) and 4.09 (95% CI 1.50–11.14), respectively. The increased mortality was seen in both cardiovascular and malignant diseases in both women and men. In contrast, low p-calcium was not associated with increased mortality, 1.00 (95% CI 0.96–1.05). Elevated p-calcium was associated with increased mortality, 1.17 (95% CI 1.13–1.22). Conclusions Low p-albumin could be a marker of an increased risk of mortality, especially in patients of younger ages. This finding should prompt diagnostic measures in order to identify underlying causes. KEY POINTS Low p-albumin and calcium concentrations have been associated with increased mortality in hospitalised patients, but this is unexplored in primary care patients. A low p-albumin concentration at baseline was a risk marker for mortality; highest in the younger age groups. Increased mortality in both cardiovascular and malignant diseases was seen in both men and women with low compared with normal p-albumin concentrations. Elevated but not low p-calcium concentrations were associated with increased mortality after 10–14 years of follow-up.