Understanding Disability Adjusted Life Years (DALY): A Comprehensive Guide

Disability Adjusted Life Years
7 Mar 2024
9 min
Table Of Content
Understanding Disability Adjusted Life Years (DALY): A Comprehensive Guide

    Hey there, health enthusiasts! Today, we are diving into the world of Disability-Adjusted Life Years, or DALYs for short. Ever wondered how we measure the impact of diseases and disabilities on a population? Well, DALYs are the answer, and we are here to explain it in simple terms.


    What are DALYs?


    Imagine you have a way of measuring not just how many people are affected by a disease but also how much it affects their quality of life. That is exactly what DALYs do! DALYs or Disability-Adjusted Life Years combine the years of life lost due to premature death with the years of productive life lost due to disability. Basically, they tell us how much "healthy" life is lost because of different health problems.


    How are DALYs calculated?

    According to WHO, the disease burden is calculated using the disability-adjusted life year (DALY). One DALY equals the loss of one year of full health. DALYs comprise two parts: Years of Life Lost (YLL) and Years Lived with Disability (YLD). YLL looks at the years of life lost due to premature death, while YLD considers the years lived with a disability or any chronic health condition. By adding these together, we get the total DALYs for a particular health issue or a whole population.

    DALY = YLLs (years of life lost) + YLDs (years lived with disability),


    DALY = Mortality + Morbidity


    The DALY score is typically expressed on a scale between 0 and 1, where 0 represents perfect health, and 1 represents death. This score allows for a standardized comparison of the impact of different health conditions on a population's health status.

    How does DALY differ from QALY?


    While DALY measures the number of years lost due to illness, disability, or early death, Quality-Adjusted Life Year (QALY) measures the number of years lived in perfect health. DALY is often used to assess the disease burden in populations. At the same time, QALY is more commonly used in high-income countries to measure improvements in quality of life.

    But why do we need DALYs?

    Well, mortality rates alone don't give us the full picture of how much a disease or disability impacts a community. DALYs help us see the overall disease burden by combining mortality and morbidity (the state of being diseased or unhealthy).


    Advantages and Limitations of DALYs


    One big advantage of DALYs is that they allow us to compare the impact of different health issues and assess the effectiveness of prevention strategies. However, there are also limitations. For example, DALYs are based on measurements from wealthy countries, which might not reflect the realities of developing nations. Additionally, the disability weights used in calculating YLD are subjective and can vary depending on who is asked.


    How do we use DALYs?


    DALYs indicate the impact of disease on a population. They can help policymakers prioritize where to allocate resources and provide a snapshot of a community's health status compared to an ideal situation where everyone lives a long and healthy life.

    What health conditions can affect DALY?

    DALY accounts for a wide range of health conditions, including communicable diseases (e.g., HIV, measles, COVID-19), non-communicable diseases (e.g., diabetes, heart disease, cancer), injuries (e.g., road accidents), congenital disabilities, mental health conditions, nutritional deficiencies, and more.


    Disease burden, 2000–2019


    • DALYs from communicable diseases like HIV/AIDS and diarrheal diseases have decreased by 50% since 2000.
    • Between 2000 and 2019, DALYs related to diabetes have surged by over 80%.
    • DALYs associated with Alzheimer's disease have more than doubled between 2000 and 2019.

    Top 10 causes of DALYs in India for both sexes of all ages (2000)

    The causes, in descending order of DALYs, are:

    • Neonatal conditions
    • Diarrhoeal diseases
    • Lower respiratory infections
    • Tuberculosis
    • Ischaemic heart disease
    • Chronic obstructive pulmonary disease
    • Road injury
    • Stroke
    • Congenital anomalies
    • Iron-deficiency anaemia


    Leading Causes of DALYs:


    Neonatal conditions emerged as the primary contributor to DALYs, with nearly 10,000 DALYs per 100,000 population. This suggests a significant burden of disease and mortality among newborns in India.

    Following closely behind were diarrhoeal diseases and lower respiratory infections. While these conditions had a substantial impact on DALYs, they fell slightly short of the burden posed by neonatal conditions.

    Tuberculosis also featured prominently among the leading causes of DALYs, indicating its significant impact on public health during that period.

    Contribution of Non-communicable Diseases:

    Ischemic heart disease as well as chronic obstructive pulmonary disease (COPD) represented a notable contributors to the overall burden of DALYs. However, their impact was comparatively lower than that of communicable diseases.


    Injuries and Other Health Conditions:

    Injuries, including road injuries and stroke, were identified as contributors to DALYs, albeit to a lesser extent than communicable diseases.

    Congenital anomalies and iron-deficiency anaemia were also significant causes of DALYs. Among these, iron-deficiency anaemia appeared to have the least impact among the top 10 causes.

    Overall, health challenges in India during the year 2000, encompasses communicable diseases, particularly neonatal conditions, dominated the top causes of DALYs, non-communicable diseases and injuries also made significant contributions to the overall burden of ill-health, disability, and premature death.


    What can you do to improve your DALY score?

    Lifestyle changes like maintaining a healthy weight, quitting smoking and alcohol consumption, increasing physical activity, and following a balanced diet can improve your DALY score. Studies show that adopting these healthy habits can add years of full health to your life.


    In a groundbreaking study involving over 33,000 individuals, researchers uncovered the profound impact of lifestyle habits on one's DALY. By examining factors like 

    1. smoking,
    2. body mass index (BMI),
    3. physical activity, and
    4. mediterranean diet.

    They found that these healthy behaviors were linked to a lower risk of chronic diseases. When combined into a simple score, those adhering to all four habits lived an average of two years longer in good health compared to those with none. These findings highlight the transformative power of even small lifestyle changes in promoting overall well-being and longevity.

    Changes in DALY scores over time can provide valuable insights into the impact of interventions and policies on population health outcomes. Decreases in DALY scores indicate successful efforts to prevent disease, promote health, and improve access to healthcare services. At the same time, increases may highlight emerging health challenges that require attention.

    The End Notes


    In conclusion, while DALYs may have limitations, they remain a valuable tool in understanding the overall health of a population and guiding public health efforts. By quantifying the burden of disease, DALYs help us work towards a healthier future for everyone. Also, adopting healthy habits and simple lifestyle changes can add years of full health to your life.

    Keep exploring, stay curious, and remember, your health matters!

    Written by
    Dr. VijayalakshmiMedical Content Writer
    AboutDr. Vijayalakshmi is a Medical Content Writer at MrMed. She completed her Bachelor of Dentistry (BDS) from Sri Ramakrishna Dental College, Coimbatore, in 2022, where she expertise in dental and clinical research. During her internship, she has also worked on various research projects and presented scientific papers in national UG seminars. Post her UG, she has upskilled in pharmacovigilance regulations and clinical trial methodology through certification courses. She is proficient in researching, writing, editing, and proofreading medical content and blogs.
    Tags :DALYs,YLLsYLDsDisability Adjusted Life YearsDisease burden