Life expectancy of Indians during the past fifty years has been steadily increasing exponentially matching the trend that took several hundred years shown in Developed countries. 23Some of the possible reasons for such exponential rises gained by Indians in years are controlling deaths caused by epidemics and pandemic infectious diseases, and absence of famines or wars since India’s independence. The high death rates due to infectious diseases were dramatically curtailed due to availability of antibiotics and further with introduction of Universal Immunization program. This was followed by improved living conditions, advances in public health, and availability of advanced medical interventions.

Figure.1: Improvements in Life Expectancy-India (1960-2009)

Source: The World Bank Group [4] 

Results from estimates of World Bank indicate that India has share of her good and bad news. The good news so far has been that Life expectancy is increasing until now and bad news is whether such rate of increase can be maintained over next few decades. Currently India has excellent health service delivery mechanisms, which are efficient in extending the lives of her people by treating chronic conditions and cancer. However, the question is whether such “improvements” in technology are addressed only to cure ailing population or can India address preventive programs aimed at decreasing the burden of obesity and chronic conditions.

Hence, the next big threat to Life Expectancy improvements appears to be stemming from obesity and chronic diseases in middle and old age, which are directly linked to an increased risk for death and morbidity. Attempts to predict life expectancy of Indian population, in terms of whether it is improving or getting worse becomes even more intricate in the absence of scientific data available for such evaluations.

Figure 2. Observed and Projected composition of age-groups for Indians (1960 to 2010).

Evidence from studies indicates that obesity and overweight in adulthood are associated with large decreases in life expectancy and increases in early mortality. [5] 678This paper aims at explaining the intricacies involved in the interplay of obesity and old age in their impact on Life expectancy.

Challenges in measuring the effects of Obesity and Old Age on Life expectancy

“Ice-berg” phenomenon

The health risks of obesity in the elderly are mostly underestimated due to survivor bias seen in the elderly people (only those who have survived fatal effects of obesity and chronic diseases), inability to separate competing mortalities due to relatively shortened life expectancy in older persons and longitudinal effects of confounding conditions (eg., smoking) are difficult to measure. [9] 

Definition of Obesity in Elderly

The appropriateness of definition of obesity in the elderly is a debatable issue. Obesity should be defined as the amount of excess fat storage associated with elevated health risk. For this practical definition, Body Mass Index (BMI) has been largely used in younger adults as well in older ages. BMI gets altered in old age due to age-dependent changes in numerator and denominator in calculation. Several studies have shown that there is age-related decline in height, probably because of spinal deformity with thinning of the inter-vertebral discs as well as loss of vertebral body height due to osteoporosis. Hence, age-dependent height decrease leads to incorrect overestimation of obesity. Body weight in old people reflects a higher amount of total fat because of age-dependent loss of lean body mass. This may lead to underestimation of obesity as a result of increase and redistribution of fat inside the body. Hence, aging influences both numerator and denominator of BMI, in opposite directions. Further, larger waist and waist-to-hip ratio have found to be significantly associated with mortality in older subjects, whilst BMI was not.

The higher the age, the shorter is the remaining lifespan for persons regardless of degree of obesity. Most obesity related consequences take years to develop even among susceptible population; hence, obesity related complications in old age are not seen if susceptible die of non-obesity-related conditions. It is observed that weight change, both weight loss and weight gain, is a strong predictor of mortality. Further, many studies showed lower mortality in subjects with lower BMI, or at least a U-shaped relation between BMI and mortality. The underlying diseases such as cardiovascular disease and cancer can result in spurious inverse relation between low body weight and increased mortality. [10] 

Interaction of Obesity, Old Age and their toll on Life Expectancy

Weight gain or fat redistribution in older age confers adverse health risks in the form of early mortality and co-morbidities amounting to functional decline. Obesity has been recognized to be associated with several disorders that confer morbidity and may also be related to increased mortality. Obesity, and more importantly body fat distribution are associated with metabolic syndrome even in old ages. [11] There is higher prevalence of both systemic and pulmonary hypertension and a higher risk of cardiovascular disease morbidity and mortality in old age, especially among those with pulmonary complications and obstructive sleep apnea syndrome (OSAS). [12] 

Role of Smoking

There is stronger evidence that smoking plays an important role in the interaction of obesity and old age. It is well known that smokers are thinner and have an elevated mortality compared with nonsmokers. However, when only people who never smoked were studied, there is an observed linear relation between BMI and mortality among older subjects, suggesting that increased mortality associated with the lowest weights were a function of cigarette smoking, and that, among never-smokers, very low weights were associated with the greatest longevity.

Summary

The steady rise in life expectancy observed in the modern era may soon come to an end and the youth of today may, on average, live less healthy and possibly even have shorter lives than their parents.

There are many challenges to delineate the association between obesity and mortality in the elderly. Since confounding effects by different variables in this association accumulate over the lifetime, it is difficult to accurately measure and account for these factors. Mortality is not the only end point that should be considered in the evaluation of the impact of overweight and obesity on health status in older people.

There is increasing evidence that obesity is reduces life expectancy due to direct and indirect causes. Obesity will not only increases the risk of death for most people at most ages, but also consistently leads to a much higher level of disability and disease at all ages. Voluntary weight loss may have beneficial health effects in elderly similar to the effects in young age. Studies on the effect of weight loss in the elderly are scarce, but they suggest that even small amounts of weight loss (between 5 to 10% of initial body weight) may be beneficial. It is well known that increased physical exercise is associated with decreased mortality risk in middle-aged as well as in older people. [13] 

India is surpassing through dual burden of diseases and consequences of obesity might take a greater toll. Hence policy makers should focus on promoting prevention and treatment of obesity related conditions, especially among old age. Based on priorities in public health expenditure, the country can effectively implement population-level interventions to reduce obesity. Health care providers should engage in complete evaluation of co morbidity and weight history, in the elderly obese persons to comprehensively address potential adverse health effects of o obesity.