When it comes to determining how or why some of her patients initially present with more significant lung destruction, MeiLan K. Han, MD, likened the role of the pulmonologist to that of a forensic investigator. While those with histories of smoking or vaping, working in a hazardous environment, being exposed to pollution, or being diagnosed with specific lung disease can justify decreased lung function and capacity, there are times when the evidence is more difficult to explain based on age and other clinical characteristics.

“You’re trying to go back through a history and weed out what initially happened when that’s usually so distant from that moment in time that you first meet these patients,” said Han, chief of pulmonary and critical care at the University of Michigan Health, Ann Arbor, Michigan.“And it’s important to realize that you cannot assume that everyone is starting off at a ‘normal’ spot.”

As research in this area continues, Han and others are advocating for the healthcare industry to promote lifestyle habits and routine lung function assessment in order to increase lung capacity and function over time among patients who are living with various conditions, as well as for those who are otherwise healthy.

Not All Lungs Are Created Equal

Assessing lung function and possible decline begins with understanding each patient’s baseline. 

The way in which the lungs grow does not necessarily run parallel with the way the rest of the body grows, said Han, which provides justification for more comprehensive evaluation even before problems arise. For example, just because a patient reaches their anticipated adult height doesn’t mean that they’ve ever achieved their anticipated lung growth — and perhaps some people never will because of genetic factors, environmental triggers, a disease, or a combination.

“The prior assumption has been that most people hit peak lung function and that it would be obvious if they hadn’t reached that point,” she said. “However, research now suggests that there are multiple trajectories for lung growth.” This has become a pivotal realization in trying to establish a baseline when assessing a patient’s current state of lung function and capacity to help avoid future decline or slow the rate of any decline.

For some, a lifelong discrepancy can begin in the womb. “And so that means that if we want patients to have healthy lungs into their 80s and 90s, then we have to start getting their lungs as well-functioning as possible,” said Han.

Although there will be variance, the average individual will achieve peak lung function by age 25, statistically speaking, said Han. But for some, a natural decline will begin not long after, or perhaps prior to that point, with anatomical tendencies such as the diaphragm growing weaker, lung tissue losing elasticity, and the rib cage becoming smaller possibly contributing. The challenge is exacerbated when these natural occurrences are combined with external risk factors and exposures, even if the difference caused by an early decrease might seem negligible initially.

“A lot of what we can see ends up being very early wear and tear — the lungs and those muscles that drive lung function are getting exposed to different types of toxins,” said Bobby Mahajan, MD, section chief of interventional pulmonology at Inova Health System in Fairfax, Virginia. “You don’t really see it significantly during an exam and nothing that will cause shortness of breath, but if you were to look at lung function longitudinally, you would see functions slowly decline. What we really want to look at is that natural breakdown and the objectively small amounts of changes.”

As with common acute and chronic conditions, Han and Mahajan emphasize prevention of smoking, vaping, and indoor and outdoor pollutants, as well as encouraging appropriate respiratory-related vaccinations for mitigating the impact of delayed lung development or earlier decline.

“There are going to be people who are born with lungs that are too small due to prematurity factors that catch up with them, and there are people who are born with healthy lungs that experience repeated respiratory infections or secondhand smoke, and they never quite meet what they’re predicted,” said Han. “So even if everyone declines at the same rate, a healthy rate, generally speaking, some people start at a place that’s not good to begin with and probably don’t even know it.”

Factors Beyond Common Triggers

Aside from smoking and pollution, there are still reasons for earlier-than-anticipated decline in lung capacity and function. One such genetically inherited factor is a deficiency in alpha-1 antitrypsin, a protein produced in the liver that protects the lungs from damage caused by inflammation, said Mahajan.

“This is what we call a homozygous mutation, where people have the absence of the protein that prevents continuous free radical breakdown of the lung,” he said. “As a result, they may be nonsmokers, but they actually lose function in their lungs, and they develop what looks like essentially an emphysema picture without ever having smoked.”

Better identification of those genetically predisposed for cancer might also help to uncover incidences of earlier loss of lung capacity and function even when those genetic complications do not inherently directly cause function and capacity issues prior to tumor growth. “The most important thing that we’re recognizing and seeing there is the genetic component of developing lung cancers in nonsmokers, known as the epidermal growth factor receptor (EGFR) mutation, specifically focusing on Asian males and females who have a higher incidence of different types of mutations that increase their risk of lung cancers,” said Mahajan. “These patients don’t fall into the typical screening guidelines of those we worry about for potential lung cancer, so they typically are diagnosed at later stages.”

Identifying people who have an EGFR mutation before they have other symptoms can be difficult for a variety of reasons, including the potential for somatic mutations that can occur any time after birth. “The tests aren’t standard of care,” said Mahajan. “But what we look at from some of the research is how to potentially develop a way of looking at these patients and testing them to see if they’re at higher risk. And we’re looking to test family members of people who have nonsmoking lung cancer to help identify more patients at risk.”

Appropriate Exams and Exercises

Despite the difficulty in achieving early diagnosis during the earliest signs of lung function decline, both Han and Mahajan suggest that there are actions that can be taken to improve the potential. For instance, when there’s shortness of breath, the goal should be to attribute this to something beyond a general lack of exercise or deconditioning, said Mahajan.

“We typically want to make sure that we’ve done an appropriate physical exam, an appropriate physical history, and at least basic office spirometry,” he said. “We want to at least perform a screening to see if there’s any abnormalities. And if something seems abnormal, then we would move to a full pulmonary function test to assess for lung function decline. As a medical community, we need to be looking out for these symptoms, doing appropriate workups, and getting screening spirometry to get more objective data.”

Mahajan expressed concern about potentially inconsistent spirometry testing in shortness of breath. “Even though it can be done in the office at a very cheap cost, it isn’t ubiquitous and being done regularly in the setting of shortness of breath,” he said. “We should not just be making assumptions. We need to have a low threshold for doing spirometry.”

“Most people will have some decline in their lung function, but if they’re getting shortness of breath with that, it means there’s typically something else driving that,” said Mahajan. He also suggests monitoring when a decline in lung function is seen without shortness of breath. “That’s worthwhile because it could be that shortness of breath hasn’t occurred yet,” he said.

From a dyspnea standpoint, there’s often mechanical issues with the diaphragm or intercostal muscles that lead to less air being brought into the lungs, which can contribute to earlier decline, explained Mahajan. “The problem is, as we get older, our muscles get weaker, and we get more deconditioned, [and] these muscles don’t function as well as they can,” he said. “The goal is to maintain muscle tone and to exercise those muscles with cardio and light resistance training that allows the muscles to grow and stay in shape. Typically, that will improve lung function and endurance in the best way possible as we age.”

Patients living with emphysema and other conditions could be at a disadvantage due to the lungs being overinflated, with possible lack of muscle function exacerbating the problem. “For these patients, we’ll enroll them in muscle-building pulmonary rehab to strengthen those breathing muscles to overcome and compensate for the other muscles that aren’t functioning very well,” said Mahajan. “To help strengthen muscles into older age, we want patients to be active and, most importantly, not allow muscles to decondition and atrophy over time.”

Potential for Prevention

Han likes to envision a reality in which pulmonary function testing occurs periodically throughout childhood, adolescence, and adulthood. “Not necessarily because we think we’re going to pick up disease at the moment that we do the test, but, rather, it would allow us to establish a curve so that we know when someone looks like to be veering off,” she said. “And then we would investigate further and talk more aggressively about avoiding risks such as smoking and vaping.”

Han and Mahajan reported serving as spokespersons for the American Lung Association.