In this study, we examined the six-decade (1960–2020) trend of LEB in Iran and compared this trend with the total Asian population. Overall, when we summarize the obtained findings via the estimated summary measure of AAPC, it can be concluded that both the Iranian and Asian populations have experienced a rather similar trend of LEB over the study period. On the other hand, a more precise comparison between these two trends indicates that Iranian males (and subsequently total Iranian population) have drastically experienced a downward LEB trend in the period of 1976–1983, while the Asian population had a rising trend of LEB with an annual percent change of 0.8 over the same time interval. This remarkable decrease in LEB of the Iranian population is directly the consequence of the revolutionary struggles in Iran and the beginning of the Iran-Iraq war in 1980.
A quick look at the reported life expectancies in the results section reveals that Iranian people have experienced about 32 years increase in LEB during the study period. Now, to describe our findings from another point of view, we can divide the study period into two different time intervals: before and after the victory of the Islamic revolution and the beginning of the Iran-Iraq war (i.e. 1960–1980 and 1980–2020). When we compare the LEB estimates between 1980 and 1960, 9.8%, 34.4%, and 20.4% increase can be observed, respectively in males, females, and the total Iranian population. Moreover, comparing the LEB estimates between 1980 and 2020 tells us that Iranian male, female and total populations have experienced about 51.0%, 31.6%, and 42.2% rise in LEB, respectively. It seems the sharper increasing slope of LEB in Iranian men compared to Iranian women from 1980 to 2020 has compensated for the considerable gap between males and females in 1980. In other words, an estimated difference of more than 9 years in LEB in 1980 has changed to about 2 years difference in 2020. These findings are completely in line with a research by Sepanlou et al. based on the reported data from the Global Burden of Disease (GBD) 2015 study (11). In addition, our reported LEB values are quite similar to those presented by other studies which used different data sets (for example national and subnational data sources) to estimate or predict life expectancy in the Iranian population (10, 12). Regardless of the destructive effect of the Iran-Iraq war on life expectancy in the early 80, the rising trend of life expectancy in Iran could be attributed to several factors such as launching a reformed primary health care system (PHC) after the Islamic revolution which decreased health inequality between urban and rural populations, increased socio-economic growth and literacy, improvement in access to health insurance, safe water, and sanitation as well as a decreased rate of malnutrition (10, 12, 17–19).
According to the presented LEBs, we can observe that the total Asian population has experienced about 28.6 years rise in life expectancy from 1960 to 2020. In addition to the identical average annual percent changes for both Asian genders (AAPC = 0.8), comparing the estimated APCs in different time intervals shows rather similar values for males and females. However, a closer look at the LEBs shows that Asian women had about 1.8 years higher life expectancy than Asian men in 1960, while this difference has increased to 4.3 years in 2020. As another noticeable result, although the Asian population has continuously experienced an upward trend of LEB over the 60-years study period, comparing the estimated APCs in different time intervals demonstrates that the steepest slope of trend has occurred in the 60s. Afterward, a sharp decrease could be seen in slopes of the trend until the ending point of the study (from APC of 2.3 in the 60s to APC of 0.3 in the last decade of the study). This upward trend of life expectancy at birth in Asian territories reflects remarkable declines in death rates, especially among mothers, newborns, and infants during the previous decades. Along with wider access to health services, improved lifestyles and living standards, better access to healthy food, drinking water, and sanitation facilities, increased rate of educated people are some of the most important indicators of this gain in longevity in the whole population across Asia (11, 20–22).
Now, it is time to compare the trend of LEB in Iran and Asia using the obtained estimates from the joinpoint regression analysis. At first glance, the estimated AAPCs look quite similar in both Iranian and Asian populations (respectively, 0.9 and 0.8). It means that Iranian and total Asian people have annually experienced less than one percent increase in LEB over the past six decades. However, some apparent discrepancies between the observed LEBs and estimated APCs for Iran and Asia could be discovered with a more precise comparison. First, in 1960 Asian people had about 0.3 year higher LEB than Iranians and this difference reached more than 6 years in 1980 and then decreased to about 0.4 year in 1990. From the early 90s, the situation was reversed in favor of Iranians so that Iranian people had a LEB of more than 3 years higher than Asians at the ending point of the study. Second, while Asians had continuously positive slopes of the trend over the study period, Iranians have experienced a negative slope during 1976–1983 as a direct consequence of the Iran-Iraq war. Third, the highest slope of LEB growth in Asian populations has occurred in the sixties (APC of 2.3), while Iranians have witnessed the highest increasing slope in the period 1983–1991 (APC of 2.7). Although, this remarkable rise in LEB during the 60s could be a direct result of the above-mentioned factors in Asia, the extraordinary upward slope of trend during the 80s in Iran might be related to some other causes. Following the Islamic revolution in 1979 and the start of the Iran-Iraq war, the revolutionary government decided to launch new policies which encouraged marriage at younger ages and child-bearing. These policies along with an influx of Afghan refugees raised the level of fertility significantly and led to the highest population growth rate of more than 4 percent from 1980 to 1986 in Iran (23–26).
In this study, we analyzed the LEB data in the period 1960–2020 to investigate the long-term trend of this vital health metric in the Iranian population. To do this, we also used similar data from the whole population as the comparison group. To our knowledge, this is the first work in this field that applies powerful inferential statistical methods for discovering the pattern of changes in LEB and identifying the trend parameters in different time intervals. However, our statistical analysis (joinpoint regression model) does not allow us to assess the effect of different related factors (such as socio-economic variables and health indices) on the trend of LEB. This can be considered as one of the most important limitations of the present study. As another limitation of the present work, it should be noted that the published similar works in this field have generally applied descriptive statistical methods to represent the pattern of LEB in different parts of the world. Since we interpreted our findings according to inferential indices such as APC and AAPC estimates, comparing these analytic measures with descriptive statistics was rather impossible.