Prevalence of zinc deficiency and its clinical relevance among hospitalised elderly.
Zinc is an essential trace element, and constituent of many metallo-enzymes required for normal metabolism. Age may be associated with altered metallothionein metabolism related to changes in zinc metabolism. The objectives of this study were: (i) to assess the prevalence of zinc deficiency among hospitalised elderly patients; (ii) to define the social, functional, pathological and nutritional characteristics of zinc deficient elderly hospitalised patients; and (iii) to assess the relationship between the zinc status and humoral immune function among hospitalised elderly patients. Fifty consecutive patients underwent comprehensive geriatric assessments included evaluations of the medical (index of the severity of the disease(s)), psychiatric (Geriatric depression scale (GDS)), therapeutic, social, functional (Katz's scale), and nutritional problems (Mini Nutritional Assessment (MNA) and biochemical markers (zinc, albumin, prealbumin (PAB), cholesterol) before their discharge. Fourteen patients (28%) presented a zinc concentrations lower than 10.7 micromol/l, this value is usually considered as the cut-off level below which a zinc deficient status is possible. Higher proportions of respiratory infections, cardiac failure, and depression were observed among zinc deficient patients as compared with the group of patients with normal zinc status. The other parameters of comprehensive geriatric assessment did not allow to discriminate the zinc deficient patients. The only slight differences (which remained unsignificant) concerned the prealbumin levels which tended to be higher in the group of patients presenting normal zinc status than in the group with poor zinc status (0.208+/-0.062 versus 0.171+/-0.068 g/l respectively, P=0.06), and the IgG2 levels which tended to be lower in the group of patients with normal zinc status than in the group presenting poor zinc status (2.77+/-1.91 versus 4.06+/-2.56, respectively, P=0.057). A negative correlation was observed between the Zn concentrations and the IgG2 levels (Spearman R=-0.311, P=0.028). To the best of our knowledge, this is the first study presenting zinc status according to a comprehensive geriatric assessment among European hospitalised geriatric patients. We decided to perform this study to known whom of our patients needed to be supplemented with zinc administration. Considering the low energy intake of hospitalised patients (confirmed here in regards of the nutritional assessment), and the insufficient trace element density in European foods, the relevance of providing medical supplements or enriched foods to this population has to be evaluated. Although most of the current diseases may be relevant to long-term interactions between nutrition and ageing, certain states observed in the elderly, like impaired immune and cognitive functions, could still benefit from an appropriate nutritional supplementation.