Abstract
OBJECTIVE—To investigate the sampling distribution and usefulness of expectation of life in comparisons of mortality at health district level or below. DESIGN—Derivation of a formula for the variance of the expectation of life, confirmation of the result and generation of the sampling distribution by Monte Carlo simulation; comparison of expectation of life with standardised mortality ratio (SMR) and other summary indices of mortality. SETTING—A health district in Trent Region, England. SUBJECTS—Routinely available mortality statistics at electoral ward level and above. MAIN RESULTS—Given reasonable and simple assumptions the sampling distribution of the expectation of life is approximately normal. Expectation of life shows a high negative correlation with SMR even if the oldest age band for the SMR is open ended. CONCLUSIONS—Where sampling error is an issue, inference concerning differences in mortality rates between populations can be based on expectation of life, which is better for illustrative purposes than SMR. The formula for the variance of the expectation of life is more complex however. If the final age band is open ended, its lower bound should be as high as possible to avoid misleading results caused by hidden differences in age structure. Keywords: life expectancy; sampling distribution; Monte Carlo method
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Selected References
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- Craig J. To be or not to be--what are the odds? Popul Trends. 1998 Summer;(92):42–50. [PubMed] [Google Scholar]
- Haybittle J. L. The use of the Gompertz function to relate changes in life expectancy to the standardized mortality ratio. Int J Epidemiol. 1998 Oct;27(5):885–889. doi: 10.1093/ije/27.5.885. [DOI] [PubMed] [Google Scholar]
- Lai D., Hardy R. J., Tsai S. P. Statistical analysis of the standardized mortality ratio and life expectancy. Am J Epidemiol. 1996 Apr 15;143(8):832–840. doi: 10.1093/oxfordjournals.aje.a008822. [DOI] [PubMed] [Google Scholar]
- Raleigh V. S., Kiri V. A. Life expectancy in England: variations and trends by gender, health authority, and level of deprivation. J Epidemiol Community Health. 1997 Dec;51(6):649–658. doi: 10.1136/jech.51.6.649. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tsai S. P., Hardy R. J., Wen C. P. The standardized mortality ratio and life expectancy. Am J Epidemiol. 1992 Apr 1;135(7):824–831. doi: 10.1093/oxfordjournals.aje.a116369. [DOI] [PubMed] [Google Scholar]