Zinc supplements for treating thalassaemia and sickle cell disease.
Author(s): Swe KM(1), Abas AB, Bhardwaj A, Barua A, Nair NS.
Affiliation(s): Author information:
(1)Department of Community Medicine, Melaka-Manipal Medical College (MMMC), Melaka,
Malaysia. khmoneminswe@gmail.com.
Publication date & source: 2013, Cochrane Database Syst Rev. , 6:CD009415
BACKGROUND: Haemoglobinopathies, inherited disorders of haemoglobin synthesis
(thalassaemia) or structure (sickle cell disease), are responsible for
significant morbidity and mortality throughout the world. The WHO estimates that,
globally, 5% of adults are carriers of a haemoglobin condition, 2.9% are carriers
of thalassaemia and 2.3% are carriers of sickle cell disease. Carriers are found
worldwide as a result of migration of various ethnic groups to different regions
of the world. Zinc is an easily available supplement and intervention programs
have been carried out to prevent deficiency in people with thalassaemia or sickle
cell anaemia. It is important to evaluate the role of zinc supplementation in the
treatment of thalassaemia and sickle cell anaemia to reduce deaths due to
complications.
OBJECTIVES: To assess the effect of zinc supplementation in the treatment of
thalassaemia and sickle cell disease.
SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders
Group's Haemoglobinopathies Trials Register comprising references identified from
comprehensive electronic database searches and handsearches of relevant journals
and abstract books of conference proceedings.Date of most recent search: 01
February 2013.
SELECTION CRITERIA: Randomised, placebo-controlled trials of zinc supplements for
treating thalassaemia or sickle cell disease administered at least once a week
for at least a month.
DATA COLLECTION AND ANALYSIS: Two review authors assessed the eligibility and
risk of bias of the included trials, extracted and analysed data and wrote the
review. We summarised results using risk ratios or rate ratios for dichotomous
data and mean differences for continuous data. We combined trial results where
appropriate.
MAIN RESULTS: We identified nine trials for inclusion with all nine contributing
outcome data. Two trials reported on people with thalassaemia (n = 152) and seven
on sickle cell anaemia (n = 307).In people with thalassaemia, in one trial, the
serum zinc level value showed no difference between the zinc supplemented group
and the control group, mean difference 47.40 (95% confidence interval -12.95 to
107.99). Regarding anthropometry, in one trial, height velocity was significantly
increased in patients who received zinc supplementation for one to seven years
duration, mean difference 3.37 (95% confidence interval 2.36 to 4.38) (total
number of participants = 26). In one trial, however, there was no difference in
body mass index between treatment groups.Zinc acetate supplementation for three
months (in one trial) and one year (in two trials) (total number of participants
= 71) was noted to increase the serum zinc level significantly in patients with
sickle cell anaemia, mean difference 14.90 (95% confidence interval 6.94 to
22.86) and 20.25 (95% confidence interval 11.73 to 28.77) respectively. There was
no significant difference in haemoglobin level between intervention and control
groups, at either three months (one trial) or one year (one trial), mean
difference 0.06 (95% confidence interval -0.84 to 0.96) and mean difference -0.07
(95% confidence interval -1.40 to 1.26) respectively. Regarding anthropometry,
one trial showed no significant changes in body mass index or weight after one
year of zinc acetate supplementation. In patients with sickle cell disease, the
total number of sickle cell crises at one year were significantly decreased in
the zinc sulphate supplemented group as compared to controls, mean difference
-2.83 (95% confidence interval -3.51 to -2.15) (total participants 130), but not
in zinc acetate group, mean difference 1.54 (95% confidence interval -2.01 to
5.09) (total participants 22). In one trial at three months and another at one
year, the total number of clinical infections were significantly decreased in the
zinc supplemented group as compared to controls, mean difference 0.05 (95%
confidence interval 0.01 - 0.43) (total number of participants = 36), and mean
difference -7.64 (95% confidence interval -10.89 to -4.39) (total number of
participants = 21) respectively.
AUTHORS' CONCLUSIONS: According to the results, there is no evidence from
randomised controlled trials to indicate any benefit of zinc supplementation with
regards to serum zinc level in patients with thalassaemia. However, height
velocity was noted to increase among those who received this intervention.There
is mixed evidence on the benefit of using zinc supplementation in people with
sickle cell disease. For instance, there is evidence that zinc supplementation
for one year increased the serum zinc levels in patients with sickle cell
disease. However, though serum zinc level was raised in patients receiving zinc
supplementation, haemoglobin level and anthropometry measurements were not
significantly different between groups. Evidence of benefit is seen with the
reduction in the number of sickle cell crises among sickle cell patients who
received one year of zinc sulphate supplementation and with the reduction in the
total number of clinical infections among sickle cell patients who received zinc
supplementation for both three months and for one year.The conclusion is based on
the data from a small group of trials,which were generally of good quality, with
a low risk of bias. The authors recommend that more trials on zinc
supplementation in thalassaemia and sickle cell disease be conducted given that
the literature has shown the benefits of zinc in these types of diseases.
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