Serum zinc and copper status in hospitalized vs. healthy elderly subjects

Objective: To assess serum zinc and copper concentrations of elderly hospitalized patients with a broad range of diseases and compare their levels to those of healthy community dwelling controls of similar age. Methods: This case-control study compared serum zinc and copper levels of 668 hospitalized subjects, aged 70 or over, with 104 healthy controls of the same age and from the same geographical area. The study protocol, conducted by one physician on the day after the admission to the hospital, included a questionnaire on sociodemographic characteristics, a medical examination, and serum zinc and copper measured with flame atomic absorption spectrophotometry. Data were analysed using analysis of covariance, controlling for age and sex. Results: The diseased subjects had markedly lower zinc concentrations than the control group. The frequency of low values (<0.70 mg/L) was high (20.2% vs. zero in controls, p < 0.001), and it differed among various disease categories: 35.7% for respiratory disease, 20%-27% for cancer, infectious disease, trauma, blood diseases, and genitourinary diseases, and less than 20% for the other diseases. Low values for serum copper concentration (<0.80 mg/L) were rare in hospitalized subjects (1.4% vs. zero in controls). Whatever the disease category and number of diagnoses considered, the serum copper/zinc ratio was significantly (p < 0.001) higher in diseased than in healthy people. Conclusions: Elderly hospitalized patients are at elevated risk of low zinc but not copper values. The significantly lower values of serum zinc found in the hospitalized elderly compared to healthy elderly are likely to be related to disease rather than to aging per se. In addition to other classic anthropometric (BMI) and biological (serum proteins) nutritional parameters, copper/zinc ratio may be a useful marker of malnutrition.