Over the past several decades, research studies have provided mixed results about how the height of a person affects his lifespan. The findings of different studies have shown conflicting results about the link between being taller or shorter and general health or mortality.
What does research say?
Some recent studies have found a negative correlation between longevity and height based on a relatively homogeneous sample of the deceased population.
These findings are based on the evaluation of the millions of deaths that suggest people with shorter and smaller bodies have a lower death rate and a reduced risk of diet or lifestyle-related chronic diseases, especially after middle age.
The trends in lifespan
The average lifespan of humans is about 70 years.
The average lifespan has been increasing steadily over the past few decades due to the advancements in the medical field and improved diagnostic tools and treatments.
However, the increased average lifespan is somewhat offset by the changes in the diets and lifestyle habits of people across the globe.
It has been found that the incidence of diet and lifestyle-linked chronic diseases like hypertension, diabetes, stroke, heart attacks, and cancer is increased gradually. And this rising incidence has contributed to the increased number of deaths at a relatively younger age.
However, the impact of lifestyle and dietary factors on the lifespan or the risk of mortality has been found to vary in taller and shorter people.
Mortality linked to chronic diseases
Studies have revealed that shorter people are less likely to develop chronic diseases due to faulty habits than taller people. Even the risk of serious life-threatening complications due to these habits is less in shorter people. This has led to an improved lifespan and better overall quality of life in people with shorter stature. 
The results of one research study have also suggested that the differences in the longevity between men and women could be linked to their heights. On average, men are about 8.0% taller than women. The life expectancy of men is also 7.9% lower than that of women at birth. This indicates the lower average height of women could be a factor contributing to their improved lifespan.
The concept of entropy
Some studies conducted to evaluate the correlation between height and lifespan are based on the concept of entropy. The Entropy Theory of Aging hypothesizes that aging could be the result of an increasing state of disorder in the body system.
This theory can be used to predict the effect of increasing body mass on the lifespan. Entropy is also considered the measure of order or disorder. When left alone, the aging mechanisms within the body continue to occur spontaneously. This causes the body to transition from being youthful and orderly with reduced entropy at a younger age to be in a state of disorder and higher entropy as age increases.
So, as children grow into adults, the increase in their height can contribute to a state of disorder thereby putting them at risk of several diseases. This is why; most diseases are common in older people than in children.
This link between height and entropy can also be applied to why taller people have a shorter lifespan and vice versa. The shorter height protects people against the age-related decline in health and thus, helps them live longer.
Study of lifespan of famous people and athletes
This concept has been evaluated in a study aimed at assessing the impact of body size on the lifespan of deceased groups of famous people and athletes in the USA. It suggested that lighter and shorter men lived longer than their heavier and taller counterparts. In another study conducted in 1990, the data of 1679 deceased men and women from the general population supported similar findings.
Important statistical data
Based on the findings of different studies, it has been found that men having a height of less than 175.3 cm usually live about 4.95 years longer than men with a height of more than 175.3 cm, on average. Also, men with a height of 170.2 cm or less have a lifespan of 7.46 years longer than that of men with a height of at least 182.9 cm.
This corroborates earlier findings and even contradicts the popular belief that taller men are healthier.
However, though these studies have shown that shorter stature can mean an improved lifespan, adopting unhealthy measures to prevent height gain is definitely not desirable. It might lead to malnutrition and illnesses that can only worsen the risk of acute and chronic diseases thus reducing lifespan. 
Differences in their biological features
The reduced lifespan of taller people may also be due to the differences in their biological features. The biological reasons can be attributed to their larger bodies having more number of cells. Having more cells would mean higher chances of them developing inflammation and cancerous changes due to which their lifespan and quality of life might reduce.
Risk of life-threatening diseases
These effects of height on the lifespan may also be modified by how it affects the risk of different diseases. In this regard, we need to take into consideration how height modifies the risk of conditions known to have a higher risk of mortality like cancer, stroke, and heart attacks.
If being taller can increase the chances of life-threatening conditions, it might mean a further reduction in the lifespan of taller patients with these diseases. Similarly, the diseases that are more common in shorter people would neutralize some of the lifespan related benefits they have due to their stature. 
From the perspective of evolution, there is a price we have to pay for enjoying the advantages and perks of being tall and that price is the reduced lifespan. 
In the end, animal experiments have also shown that smaller animals of the same species usually live longer. The relation between health and height has become more vital in recent years due to the rapid development in genetic engineering that offers an opportunity for parents to increase the height of their kids in the future. However, caution must be exercised while adopting these strategies. It is advisable to not get swept along into the world of increasingly taller generations without considering the impact of the worldwide population of taller people.