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Zinc

Zinc has been shown to reduce the duration and severity of diarrheal episodes and likelihood of subsequent infections for 2-3 months. Zinc is generally well tolerated by both children and caregivers and is effective regardless of the type of common zinc salt used. Zinc is usually prescribed at a dosage of 20 milligrams per day for children older than six months or 10 mg per day in those younger than six months, for 10–14 days1.

Unit of intervention1 strip of 7-10 tablets

Formula20 milligrams of elemental zinc per tablet

Treatment course for an episode of diarrhea1 strip of 7-10 tablets

Target populationChildren under five with diarrhea

For informaiton about how PSI is increasing access to zinc to improve health and save lives, visit our website at
http://www.psi.org/health-area/child-health/diahhreal-disease/

Model Overview

PSI’s zinc impact model is based on the Lives Saved Tool (LiST). LiST is used to estimate the number of deaths averted with complete coverage of zinc for treatment of diarrhea among children under age five in a country. This number of deaths averted at the population level is translated to deaths averted per zinc treatment, using parameters such as the baseline coverage of zinc, the number of zinc tablet packs needed per episode of diarrhea, and under-five mortality rates. Once we have deaths averted per zinc treatment, we apply data from the 2010 Global Burden of Diseasestudy to estimate the corresponding number of DALYs averted.

Model Outputs (impact metrics)

Estimates of DALYs averted, deaths averted, CYPs provided, and unintended pregnancies averted represent the projected health impact of the intervention. It is projected because it has not been directly measured.

Examples based on distribution of zinc tablets in Myanmar Statement of modeled results, examples:

In 2015, an estimated 7 deaths and 619 DALYs would be averted if 100,000 strips of zinc tablets were distributed in Myanmar.

For more details about how PSI models the impact of zinc, see below.

Model Details

Step 1: Running a projection in the Lives Saved Tool (LiST)LiST is a multi-cause mortality model developed by Johns Hopkins Bloomberg School of Public Health that estimates the number of deaths averted (or lives saved) through the scale up of maternal and child health interventions.

PSI begins by running a projection in LiST for a selected country. In this projection, coverage of zinc is increased from the current, country-specific baseline to 100% among children under five. LiST then projects the number of deaths averted by this increased level of coverage.

Step 1 Output:
Number of deaths averted (or lives saved) if coverage of zinc is increased to 100% among the children under age five years in a given country

Step 2: Estimating deaths averted per strip of zinc tablets (deaths averted coefficient)PSI uses the step 1 output (deaths averted at 100% coverage of zinc) to estimate the number of deaths averted by a single zinc treatment. To do this, we divide the number of deaths averted at 100% coverage by the number of zinc treatments needed to reach 100% coverage.

PSI estimates the number of zinc treatments needed to reach 100% coverage using a number of parameters, including baseline coverage of zinc, the number of zinc tablet packs needed per episode of diarrhea, and diarrhea incidence rates. Each case of diarrhea is assumed to require one treatment pack of zinc. We also account for wastage of zinc packets in the supply chain, assumed to be 10%.

Step 2 Output:
Deaths averted coefficient

Step 3: Estimating DALYs averted per strip of zinc tablets (DALYs averted coefficient)A DALY (or disability adjusted life year) includes two components: years of life lost due to premature death (YLL) and years lived with disability (YLD). DALYs averted are in turn comprised of YLLs averted and YLDs averted or, put simply: death and disability that is prevented by PSI interventions.

To estimate YLLs averted per unit of zinc, PSI first estimates the number of years of life lost per diarrhea death among children under five in a selected country. This is equal to the life expectancy at the average age of death from diarrhea. Age specific life expectancy is taken from the 2010 Global Burden of Diseasestudy (GBD 2010). The number of years of life lost per diarrhea death is then multiplied by the number of deaths averted per packet of zinc (deaths averted coefficient), calculated in step 2 above for a selected country. This gives us the YLLs averted per unit of zinc.

To estimate YLDs averted per unit of zinc, we use a YLD/YLL ratio, based GBD 2010. This ratio represents the relative number of years lived with disability for every year lost due to death from diarrhea in a selected country. We apply this ratio to the number of YLLs averted per packet of zinc to estimate the number of YLDs averted per packet. Because zinc treats diarrhea, we assume that individuals will still suffer some disability before and during treatment. Therefore, we only include half of the total YLD averted in our estimate. This is a standard assumption in all of our treatment models.

Finally, YLLs averted and YLDs averted are added together to estimate the number of DALYs averted per packet of zinc.

Step 3 Output:
DALYs averted coefficient