Disability-adjusted life years (DALYs) are a universal measurement that researchers and policymakers use to calculate how diseases and medical conditions affect the length and quality of life for a given population. Basically, one DALY equals one year of full, healthy life that you may lose because you're sick and have a high risk for certain conditions, disabilities, or due to death. The number of years may add up based on how severe your illness might be. The DALY is used to understand and evaluate the “burden of disease” in different populations. This means experts look at the health, socioeconomic, political, environmental, and economic factors that affect overall health outcomes. DALYs were first used in the early 1990s. Experts also use it to compare how certain conditions affect the total number of years lost across different populations locally, regionally, and globally. To calculate DALYs, experts use two other health metrics: YLLs refers to the number of years of life lost due to premature death. YLDs refer to the causes and number of healthy years one might lose from their life due to disability and sickness. DALY is calculated as the sum of YLLs and YLDs due to health conditions or diseases that affect a particular population. The DALY scale is between 0-1. 0 implies perfect health while 1 equals death. For example, if you take a look at a set of people who are 15 years old, you might assume that they'll live to close to 80 if they don't develop severe health conditions like diabetes, asthma, a road injury, or cancer. However, if one of them dies at age 15 due to a car accident, you can calculate DALY as 80 minus 15 YLL (years of life lost due to death). In this case, you can skip YDL as there's no health condition or disability involved. 80 minus 15 would equal 65 DALY – each point for a year of healthy life lost. You can add back DALYs, or full years of healthy, productive life, to the overall score if you get treatment, make lifestyle changes, or get medical procedures to improve your health outcome. DALY takes into account a wide range of health conditions, injuries, and disabilities that affect a given population to calculate a score between 0 and 1. This can include: Like DALY, quality-adjusted life year (or QALY) is another popular metric that experts use to measure the length and quality of life of an individual. It's basically 1 year of life you live when you're in perfect health. This metric is mostly used in high-income countries in the West. The difference in approach between the two metrics is that while DALY is often used to measure the number of years lost due to sickness or death, QALY is used to measure the number of years you might gain when your quality of life improves. Research shows you can improve the total number of years lived in full health and lower the burden of disease if you: One study that looked at over 33,000 men and women found that if you make and stick to all of the lifestyle changes toward a healthier life, it can improve your DALY score. Not only will it boost your overall health outcome but also add a minimum of 2 years of full health to your life compared to those who don't make any lifestyle changes. DALYs allow experts and policymakers to take a large-scale look at what level of burden a particular disease might have on a given population and make recommendations to improve accordingly. Studying the burden of disease can help understand: For example, if you take a look at young people between ages 10-24, they have many more years of healthy life to live, and usually, death or severe illness is rare among this population. DALY scores can allow researchers to look at the impact of certain conditions such as growing cases of diabetes or heart disease, or physical disabilities, and see how it can affect their ability to live a long, healthy life. This information can be used to improve health services, make recommendations for healthier lifestyles to live longer lives, and guidelines for particular age groups. DALY uses only a single number to account for all the costs and losses caused by diseases or disabilities, but it might not take the full picture into account. That's because not all diseases or disabilities are equal nor is your ability to manage them. For instance, having asthma for a few years is not the same as living with schizophrenia. So it's complicated to calculate without taking into account the social factors that affect different international populations' health outcomes. For example, disabilities such as injuries, illnesses, and developmental problems such as speech or hearing don't necessarily mean that you cannot live a full, healthy life. In fact, your overall quality of life might vary significantly depending on where you live and whether you have access to quality health care, social support, accommodations in your immediate environments to help you with your daily activities, and your ability to get timely medical treatment or rehab