1. Calculating Ward Level Life Expectancy Peter Fryers Public Health Information Specialist West Midlands Public Health Observatory

2. Ward Population Data 1991 Census Ward Population –Adjusted to 1998 Ward boundaries –Using Estimating with Confidence ED Populations 1998 ONS Mid-Year Estimates –Local Authority Based –5-year age band 1998 Oxford University Ward Estimates –Sexes combined –3 broad age bands (0-15, 16-59, 60+)

3. Population Calculation Iterative Process Totals add up to –ONS mid-year estimates 15-19 age group split by 15 and 16-19 –Oxford University ward estimates Starting values 1991 ward populations adjusted to 1998 ward boundaries –15-19 age group split by 15 and 16-19 –Effectively three tables 0-15, 16-59, 60+

4. Population Table Structure 0-4, 5-9, 10-14, 15 OU 0-15 16-19, 20-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59 OU 16-59 60-64, 65-69, 70-74, 75-79, 80-84, 85+ OU 60+ Wards … LA Total Wards … LA Total

5. Iterative Process Starting with 1991 figures adjust proportionally 1.Adjust ward population to OU age totals –i.e. adjust across 2.Adjust result of (1) to ONS LA totals –i.e. adjust down 3.Repeat from (1) using result of (2) –Repeat until difference to OU totals is less than 0.001

6. Life Expectancy Methodology after Silcocks et al –Exponential survival in final age band Assumption tested using Monte Carlo simulation –Calculation of 95% confidence intervals Silcocks PBS, Jenner DA, Reza R (2001) Life Expectancy as a summary of mortality in a population: statistical considerations and suitability for use by health authorities. J Epidemiol Community Health 55:38-43 http://jech.bmjjournals.com/cgi/content/full/55/1/38

7. Life Expectancy L1L1 L 2 = proportion alive at end of 2 nd age band L3L3 L n-1 LnLn A 2 = area of 2 nd age band W2W2 L 0 (=1) = width of 2 nd age band

8. Final Remarks Main problems associated with Population not Life Expectancy Problems in areas with high proportion of people living in nursing homes Correlates well with other measures of mortality as well as deprivation measures 95% confidence intervals vital at small area level