Written by Tim Peterson, assistant professor in the Department of Medicine at Washington University in St. Louis
While more and more people are taking an interest in aging and lifespan, awareness on healthspan lags (Figure 2). If you don’t know what healthspan means you aren’t alone. What is healthspan?
Many might agree that “healthspan” can be defined as the period of one’s life that one is healthy. However, being “healthy” means different things to different people. A better definition might include being free from serious disease. A disease is considered to be serious if it is a leading cause of death (Table 1).1
Why do we care about healthspan? Caring about extending the well period of one’s life should be intuitive – if one is past their healthspan, it means they are chronically sick, often with a degenerating condition. Therefore, most people would agree that staying within their healthspan is desirable.
In an extreme case, Ezekiel Emmanuel, the brother of President Obama’s chief of staff Rahm Emmanuel, doesn’t want medical interventions past the age of 75.2 To paraphrase his argument, he only wants to live if he can live well.
Healthspan is a socioeconomic issue, too. There is a widening gap in life expectancy in different geographic regions of the US.3 Because lifespan and healthspan are intimately related, focusing on healthspan should help level the wellness playing field for more people.
What can we do about healthspan? First we need to measure it. Once we measure it, then we can improve it. While there are good biomarkers for a few of the serious diseases like heart disease, e.g., cholesterol levels, there aren’t good biomarkers for other leading causes of death, such as most cancers. Because we have trouble predicting whether someone may get a serious disease, how do we get a handle on healthspan?
Unlike average lifespan, which is now 79.3 years in the US, we don’t have a statistic to mark the end of the average healthspan. To address this, the World Health Organization (WHO) has developed an indicator, HALE – healthy life expectancy.4 A simple way to approximate HALE is to figure out the average age of the first occurrence of each of the most common serious diseases, determine their incidences, and then take the average of those two numbers (Table 1). This gives us 63.1 years old (which is close to the 2015 HALE estimate of 67.3 years old, Figure 1).
This means that we, on average, live up to 20% of our lives unhealthy. Needless to say, that is a long time.
To improve upon these statistics, we need treatments. Treatments don’t necessarily mean drugs, so let’s break them down into molecular and non-molecular approaches. First, there are many commonalities around lifestyle that could delay the onset of most, if not all, of the serious diseases. It might seem like common sense, but maintaining a healthy balanced diet with moderate, regular exercise and without smoking and drinking alcohol is the surest way to promote one’s healthspan and limit the onset of most diseases. The Mediterranean diet has fairly broad support in the literature.5
Regarding the molecular basis of healthspan, there is growing evidence on several dietary and cellular components that improve our body’s function. Fatty acids, energy “currencies” such as glucose and oxygen, and antioxidants such as NAD+ have been shown to influence the health of various tissues and their stem cells in many different species.6 Stem cells are interesting because they are important to tissue regeneration – a process directly involved in keeping our bodies healthy. Experimental treatments such as rapamycin and metformin, and dietary manipulations (e.g., caloric restriction, fasting mimicking) also have shown promise as longevity-promoting therapies. Still, it should be noted that many human clinical trials show conflicting results for the aging-preventing abilities of most natural or non-natural compounds (for clarification, see Notes below). Therefore, one should take caution in interpreting any study highlighting anything resembling a cure-all molecule.
Social, intellectual, and physical activities are also huge healthspan determinants.7 Even though they may be more commonly associated with psychological effects, their strong physiological effects should not be ignored. They should be treated by medical professionals as frontline approaches alongside medicines.
Healthspan is a topic relevant to all people with huge social and economic consequences around the world. While younger people might benefit most in the long-term from an increased focus on healthspan-moderating therapies, older adults might be first to see benefits. This is due to the simple fact that research involving older adults gets to the study outcome, either good or bad, faster. Therefore, to conclude with a plug for aging research, the time is now to get involved!
Notes: By natural compounds, I refer to naturally occurring molecules – vitamins such as vitamin C and vitamin D, metabolites (i.e., small molecules such as fatty acids, glucose, and amino acids) and minerals such as calcium, iron, and zinc. By non-natural compounds, I mean chemicals synthesized in a lab such as many FDA-approved drugs.
This post centers on health topics in the U.S. Please refer to the World Health Organization and other internet sources such as PubMed for fuller discussions of health trends in other countries.