Life expectancy at birth measures the average number of years that a newborn baby can expect to live. This estimation is based on the mortality rates of the population in a given year. During the time of Roman Empire, an average citizen might expect to live 28 years. By the turn of 20th century, a person in advanced country could expect to live around 50 years. In the early 21st century, a Japanese woman reaching 84 would not be unusual. In India a person born in 1920 could anticipate celebrating his or her birthday only 32 times. With improved sanitation and public health along with chemotherapy, an Indian can expect to live today over 60 years and the life expectancy is estimated to cross 76 years by 2021.

Life expectancy statistics

Life expectancy statistics are used for many purposes. Various countries utilize these data to know if a particular population is living longer in comparison to other population group. These statistics are very often used to know the effect of mass immunization programme. Insurance and financial institutions, particularly in developed nations, have an interest in life expectancy data. Health administrators of countries make resource available for undertaking research to address the underlying causes of prevailing life expectancy.

What is DALE?

Previously life expectancy estimates were based on the overall length of life based on mortality data only (as mentioned earlier). For the first time ever, the WHO has developed a new measure of population health, for babies born in 1999, is disability-adjusted life expectancy, or DALE, which measures the equivalent number of years of life expected to be lived in full health, also called healthy life expectancy. To calculate DALE, the years of ill-health are weighted according to severity and subtracted from expected overall life expectancy to give the equivalent years of healthy life. Following is the formula used to estimate DALE:

DALE = LE - DLE

Where LE is total life expectancy based on average numbers of years, males and females could expect to live in each country. DLE is expected years lost due to disability - an estimate of the total equivalent lost of years of good health.

Healthy life expectancy

Why healthy life expectancy? Life expectancy at birth increased dramatically during 20th century and will continue to rise as soon as cancer and other life-threatening diseases are conquered. However, higher life expectancy is desirable only if it is linked to acceptable level of quality of life. With a longer life span the subject of healthy years of life to be lived has become important issue. Sociologists and other scientists of every country are interested higher level not only life expectancy, but also years of healthy life. Hence disability-adjusted life expectancy, DALE has become more salient. Today DALE indicator, as proposed by Mathers et al (Mathers CD et al, GPE discussion paper no 16, Geneva, WHO, 2000) is widely used sociological tool.

Table 1: Countries with highest and lowest DALE and life expectancy at birth in 1999
Rank Country DALE Life expectancy in 1999 Disability at birth, DLE
Male Female Male Female
1 Japan 74.5 77.6 84.3 5.7 7.1
2 Australia 73.2 76.8 82.2 6.0 6.7
3 France 73.1 74.9 83.6 5.6 6.7
4 Sweden 73.0 77.1 81.9 5.9 7.0
5 Spain 72.8 75.3 82.1 5.5 6.4
134 India 53.2 59.6 61.2 6.8 7.7
187 Botswana 32.3 39.5 39.3 7.2 7.1
188 Zambia 30.3 38.0 39.0 8.0 8.3
189 Malawi 29.4 37.3 38.4 8.0 9.0
190 Niger 29.1 37.2 40.6 9.0 10.5
191 Sierra Leone 25.9 33.2 35.4 7.4 9.5

Source: World Health Report 2000

DALE ranking

The DALE ranking has placed India at the 134th position among 191 nations, with an estimated life expectancy of 53.2 years at birth in 1999 (Table 1). DALE in India was 53.5 years for women and 52.8 years for men in 1999. Sri Lanka (76 rank) and China (81 rank) are much ahead of us in terms of health performance. Even, Pakistan has been placed 124th rank. Bangladesh is a bit behind us at 140.

Japan leads the world with DALE of 74.5 years at birth in 1999 (Table 1). After Japan, subsequent places are Australia, France, Sweden and Spain, with DALE ranging between 72.8 and 73.2. The UK has been placed 14th while the US is at 24th. All of the bottom countries are in sub-Saharan Africa, where AIDS epidemic is rampant. Sierra Leone is at the bottommost country with DALE of 25.9 years at birth in 1999. Life expectancy in these countries has been reduced by 15-20 years in comparison with life expectancy without AIDS.

Gap between LE and DALE

The gap between LE and DALE corresponds to DLE. DALE at birth is higher for women than men in most countries. However, although women live longer, they spend greater amount of life with disability. Genetically speaking, a baby born in Indian village is no different than a baby born in Tokyo. But the Indian baby has to face more communicable diseases, unsatisfactory food and water supplies, and lack of medical care. All of those factors led to a DALE of 53.2 in 1999. That's why health outcomes, in terms of DALE, is directly linked to access to medicines (The World Medicines Situation 2004). A quote, "Die young, but as late as possible" by Doll, R in British Medical Journal, 1, 445-453, 1983, is more relevant today than 1983. People today want to live longer with a tennis bat in hand. In recognition of present day need, the DALE indicator developed by WHO is important sociological tool and it will further promote analysis of health performance of poorly performing health systems of the world.

(The author is with Department in PharmacyAnnamalai University, Annmalainagar 608 002 (TN) Email: cdl_scbasak@sancharnet.in)