What does a $100 million public health data revolution look like?

TEDMED
23 May 201314:08

Summary

TLDRThe speaker discusses the importance of real-time health data in managing complex systems, exemplified by Rio de Janeiro's smart city initiative. They introduce a global health data tool, created by 500 experts over five years, which provides insights into disease patterns by age, sex, and locality for 187 countries. The tool reveals a shift from child mortality to non-communicable diseases in aging populations, with significant variations across countries. It also identifies leading risk factors like diet and smoking in the U.S., emphasizing the tool's potential to transform population health by learning from global patterns.

Takeaways

  • 🚗 The speaker uses the metaphor of getting to a destination, emphasizing the importance of clear information, roadmaps, and anticipating obstacles for success.
  • 🏙️ The evolution of smart cities like Rio de Janeiro, which gather real-time data to manage complex systems, is highlighted as a model for efficient responses in large cities.
  • 🌍 Over 500 experts from 50 countries have compiled global health data covering more than 1,000 clinical outcomes for 187 countries over two decades, providing invaluable insights.
  • 📊 From 1990 to 2010, the world saw significant progress in reducing child mortality and shifting the burden of disease to older populations, especially heart disease and cancer.
  • 👶 While deaths have decreased, premature mortality in children remains a large issue, with neonatal causes, diarrhea, pneumonia, and malaria still prominent in many areas.
  • 🧠 Mental and musculoskeletal disorders, along with hearing and vision loss, are significant contributors to global health problems, even though they do not cause direct mortality.
  • 🌍 The burden of disease varies greatly by region, with West Africa facing primarily communicable diseases and China having transitioned to non-communicable diseases like heart disease and cancer.
  • 📉 China has made remarkable progress in reducing communicable diseases by 80% since 1990, although it faces rising challenges from ischemic heart disease, offering lessons for other nations.
  • 🍽️ Risk factors like diet, smoking, obesity, and high blood pressure dominate health loss in the U.S., highlighting lifestyle changes as critical to improving overall health.
  • 🔬 The project combines data, science, and visualization tools to give everyone—not just specialists—access to a deep understanding of global health patterns, helping to improve public health at the community level.

Q & A

  • What is the key message of the speaker's introduction regarding reaching a destination?

    -The speaker emphasizes the importance of knowing how to reach a destination, including factors such as means of transport, clarity of the destination, potential obstacles, and tools to navigate the route. This analogy introduces the complexity of managing systems, particularly in health and first-response contexts.

  • What is the role of smart cities in first-response management, as explained in the transcript?

    -Smart cities, like Rio de Janeiro, gather real-time data to manage complex systems such as first-response services. This allows the city to handle emerging problems more effectively and ensure timely responses to emergencies.

  • What significant health data collection project does the speaker mention?

    -The speaker mentions a project involving 500 people from 50 countries who, over five years, compiled health data on more than 1,000 clinical outcomes for 187 countries. This dataset spans two decades and provides insights into global health patterns, including progress made in various health conditions.

  • What are the key insights from global child mortality trends between 1990 and 2010?

    -Between 1990 and 2010, global child mortality decreased significantly from 12 million to 7 million deaths. There was also a shift in the age distribution of deaths, with more people living to age 80 or older, showing global health improvements over time.

  • Why does the speaker emphasize premature mortality when discussing global health?

    -The speaker highlights premature mortality to emphasize that not all deaths are equal in terms of life years lost. For example, a death at age five results in more years of lost potential life compared to a death at age 95. This concept helps better understand the broader impact of early deaths.

  • What are some of the major health issues affecting young adults globally, according to the transcript?

    -Major health issues affecting young adults include HIV/AIDS, tuberculosis, road accidents, homicide, and suicide. These conditions contribute significantly to premature mortality in this age group.

  • What does the speaker mean by 'what ails you globally isn't actually what kills you'?

    -The speaker is referring to the distinction between conditions that cause death and those that cause non-fatal health problems. While conditions like heart disease and cancer may be leading causes of death, mental disorders, musculoskeletal disorders, and sensory impairments (e.g., vision and hearing loss) are major contributors to global health problems that don't necessarily result in death.

  • How has the burden of disease in China shifted between 1990 and 2010?

    -In 1990, 25% of the disease burden in China was from communicable diseases. By 2010, this figure dropped significantly, and non-communicable diseases such as heart disease, cancer, and mental disorders now account for 80% of the disease burden. This reflects China's success in reducing infectious diseases but highlights new challenges with non-communicable diseases.

  • What are some of the leading risk factors for health loss in the United States?

    -In the United States, the leading risk factors for health loss are poor diet, smoking, obesity, high blood pressure, high blood sugar, physical inactivity, and alcohol use. These factors contribute significantly to the country's overall health burden.

  • What are the three main takeaways the speaker wants the audience to remember about global health data and tools?

    -The speaker's three main takeaways are: (1) The tools allow us to ask new and insightful questions about global health; (2) We can learn from both successes and failures across the world to improve health outcomes; and (3) These tools empower everyone, not just specialists, to engage in improving health globally.

Outlines

00:00

🚑 The Role of Data in First Response and Global Health

The speaker opens by asking the audience to consider the importance of information in reaching a destination, particularly in emergency responses within large cities. He introduces the concept of smart cities, such as Rio de Janeiro, where real-time data is used to manage emergencies. The discussion then shifts to a global scale, focusing on health systems and how data collection over the last two decades—covering thousands of clinical outcomes for 187 countries—has provided insights into disease patterns. The speaker highlights the availability of this data online and emphasizes the progress in reducing child mortality between 1990 and 2010.

05:03

📊 Premature Mortality and Health Complexity

The speaker dives deeper into the issue of premature mortality, explaining how years of life lost is a better measure than just counting deaths. He illustrates the burden of diseases like diarrhea, pneumonia, and malaria, particularly in children, but also brings attention to young adult mortality from causes like HIV and road accidents. He emphasizes that health is more than avoiding death, mentioning that diseases such as mental disorders, musculoskeletal issues, and vision loss contribute significantly to the global health burden. The discussion moves toward country-specific health challenges, showing how non-communicable diseases have become more prevalent in countries like China.

10:06

📉 Tracking Changes in Disease Burden Over Time

The speaker introduces a ranked list comparing health loss in China from 1990 to 2010, showing the dramatic reduction in communicable diseases like tuberculosis and pneumonia, alongside a rise in ischemic heart disease. This comparison underscores the significant epidemiological shift in China over two decades. The speaker stresses that these trends offer lessons for both China and other developing nations on managing health transitions and emphasizes the value of understanding specific diseases for targeted health interventions.

🛡️ The Impact of Risk Factors on Health

The speaker shifts to the topic of risk factors, presenting the U.S. as a case study. He lists diet, smoking, obesity, high blood pressure, and physical inactivity as the leading contributors to health loss. The speaker reiterates the importance of using data to explore risk factors and health outcomes in different populations, encouraging the audience to explore these tools themselves. He introduces the idea that these risk factors can be modified both individually and at the community level to improve public health outcomes.

🌍 The Power of Data in Global Health Improvement

The speaker recounts a personal story about his parents' work in healthcare, which inspired his career in understanding global health patterns. He reflects on the challenges of synthesizing health data from various sources and regions, emphasizing the need for robust science to account for biases and inconsistencies in data collection. He celebrates the emergence of data scientists and advanced visualization tools that now make this complex data accessible to everyone, enabling better health interventions worldwide.

🏥 Lessons from Life Expectancy Disparities

The speaker concludes with a powerful illustration of health disparities within the U.S., showing that life expectancy can vary by up to 12 years depending on the county. He uses this disparity to emphasize the potential for health improvement by studying successful health interventions in different communities and regions. He advocates for a collective effort to use data to ask new questions, learn from global successes and failures, and empower everyone to contribute to better health outcomes, not just specialists.

Mindmap

Keywords

💡Smart Cities

Smart cities are urban areas that use technology and real-time data to manage resources and services more effectively. In the video, Rio de Janeiro is highlighted as a smart city where real-time data helps manage first responders and urban systems, ensuring quicker responses to problems. This concept is used to draw parallels with global health systems, emphasizing the importance of data for effective management.

💡Global Health Data

Global health data refers to the collection of health-related information from different countries, allowing for the analysis of diseases, clinical outcomes, and health trends. The speaker mentions a massive effort to compile health data from 50 countries over 20 years, providing insights into disease patterns and helping to inform health policies worldwide.

💡Premature Mortality

Premature mortality refers to deaths that occur before the expected age, often due to preventable causes. The video discusses the global agenda to tackle premature deaths, especially in children, and the progress made in reducing child mortality from diseases like pneumonia and diarrhea between 1990 and 2010. Premature mortality is used to emphasize the importance of early intervention and healthcare improvement.

💡Non-communicable Diseases (NCDs)

Non-communicable diseases are medical conditions not caused by infectious agents, such as heart disease, cancer, and mental health disorders. The video highlights the growing burden of NCDs in countries like China and the US, where heart disease and cancer are major causes of health loss. It contrasts these with communicable diseases, which are declining in some regions.

💡Communicable Diseases

Communicable diseases are illnesses caused by infectious agents like bacteria, viruses, or parasites. In the video, diseases like diarrhea, pneumonia, and malaria are mentioned as leading causes of child mortality, particularly in developing regions like West Africa. The speaker contrasts the prevalence of communicable diseases in these regions with the rise of non-communicable diseases in other parts of the world.

💡Burden of Disease

The burden of disease refers to the impact of health problems on a population, often measured in years of life lost or health deteriorated due to illness. The video discusses the shifting burden of disease globally, from communicable diseases to non-communicable ones, and the differences in disease burdens across countries like China, India, and the US.

💡Risk Factors

Risk factors are behaviors or conditions that increase the likelihood of developing a disease or health condition. In the video, the leading risk factors in the US, such as poor diet, smoking, obesity, and high blood pressure, are highlighted as major contributors to health loss. Understanding risk factors helps in targeting interventions to improve public health.

💡Health Visualization

Health visualization refers to the graphical representation of health data to make complex information easier to understand. The video emphasizes the power of visualization tools to explore global health trends, disease burdens, and health outcomes by region and risk factor. These visualizations enable both specialists and the general public to engage with the data.

💡Epidemiological Shift

An epidemiological shift is a change in the patterns of health and disease in a population over time. The video explains how China experienced such a shift, reducing the burden of communicable diseases like tuberculosis and increasing the prevalence of non-communicable diseases like heart disease between 1990 and 2010. This shift is used to illustrate broader global health trends.

💡Health Disparities

Health disparities refer to the differences in health outcomes between different populations, often due to socioeconomic, geographic, or racial factors. The video highlights disparities in life expectancy within the US, showing how counties in some parts of the country have life expectancies similar to developing nations like Libya. Understanding health disparities is key to addressing inequalities in health access and outcomes.

Highlights

Smart cities like Rio de Janeiro are using real-time data to manage complex systems, first responders, and urban challenges.

A global health database has been compiled by 500 people from 50 countries over five years, covering over a thousand clinical outcomes for 187 countries.

The data provides insights into patterns of disease by age, sex, and locality, highlighting areas making progress and those that are lagging behind.

Child mortality worldwide has decreased from 12 million deaths in 1990 to 7 million in 2010, with a shift in deaths to older populations.

Premature mortality is a key focus, showing significant loss of years of life in children due to preventable causes like diarrhea, pneumonia, and neonatal issues.

In young adults, diseases like HIV, tuberculosis, road traffic accidents, and mental health disorders are major causes of premature death.

Global health is not just about mortality but also the burden of disease, with mental disorders, musculoskeletal issues, and sensory impairments like hearing and vision loss contributing significantly.

Health outcomes vary greatly by country, with countries like China showing a shift from communicable to non-communicable diseases over the past two decades.

China has reduced its communicable disease burden by 80% since 1990, while ischemic heart disease has risen by 50%.

The tool developed allows users to visualize health loss from both diseases and risk factors, highlighting dietary risks, smoking, obesity, and high blood pressure as major contributors in the U.S.

Data collection from various sources, including handwritten records, is crucial to understanding global health patterns, despite biases and inconsistencies in medical reporting.

A new generation of data scientists is using advanced techniques to turn raw health data into actionable insights.

Visualization tools make complex health data accessible, helping users engage with information and ask new questions about global health trends.

The tool highlights disparities within countries, such as U.S. counties where life expectancy for women is equivalent to that in Libya.

By learning from both successful and struggling regions, communities can 'leapfrog' in improving health outcomes globally, benefiting from shared knowledge.

Transcripts

play00:25

so I want to start by getting you to

play00:27

think about a question if you want to

play00:30

get to a destination what's going to

play00:32

help you to get there now some of you

play00:35

are going to be thinking about a means

play00:37

of transport clarity of where you want

play00:39

to go maybe a road map and you want to

play00:42

know about obstacles along the way

play00:44

traffic jams weather road closures road

play00:48

construction now imagine for a moment

play00:50

that you're in charge of first

play00:54

responders in a large crowded city and

play01:00

those that information is even more

play01:04

important because it really matters

play01:06

getting the response the people in need

play01:09

and so we're seeing the evolution of

play01:11

smart cities this is Rio de Janeiro

play01:14

where they've real-time gather

play01:16

information so that they're able to

play01:19

manage a complex system manage

play01:21

first-response manage problems that

play01:24

emerge in a number of systems in that

play01:26

city what if we had that information for

play01:31

even more complex things like the

play01:33

world's health systems now the good news

play01:37

which we already heard a little bit

play01:39

about is that that information is

play01:42

actually now being put together so 500

play01:44

people from 50 countries over five years

play01:49

have put together all the world's data

play01:53

on an enormous number of conditions more

play01:56

than a thousand different clinical

play01:58

outcomes by age by sex for 187 countries

play02:02

over the last two decades giving us

play02:05

insights into where the pattern of

play02:08

disease is by age by sex by locality

play02:11

who's making progress who's not and as

play02:15

we heard that information is not just in

play02:18

a commanding control center like we saw

play02:21

for Rio de Janeiro but that information

play02:23

is online you can go get it now and

play02:25

hopefully you'll go get it after this

play02:27

presentation so there's a billion

play02:30

results in this accumulation of the

play02:34

world's

play02:35

health data and I'm going to give you a

play02:37

sort of world quick tour of some of the

play02:40

insights you can get from these tools so

play02:43

let's start with something very simple

play02:45

and that is death death by age so this

play02:50

is one of our live tools it shows in

play02:52

this case death for the world in 1990

play02:56

and there are four age groups on the far

play02:58

left for children and there are all the

play03:02

other age groups up to eighty plus and

play03:04

you can see 21 groups of causes yellow

play03:06

sticks out that's diarrhea pneumonia a

play03:08

big killer of children the dark blue is

play03:11

heart disease the lighter blue is cancer

play03:13

and from 1990 to 2010 we had a lot of

play03:16

progress in the world so let's see that

play03:18

again go back to 1990 go forward to 2010

play03:22

and what you see is that we've reduced

play03:24

child mortality in the world from about

play03:26

12 million deaths to about 7 million

play03:27

deaths and we've had a big shift to

play03:30

death over age 80 progress but deaths

play03:34

don't tell the whole story in fact if

play03:38

you die at age five you've lost most of

play03:40

your lifespan if you die at age 95

play03:42

you've lost much less and so we have to

play03:46

help get the big picture a construct

play03:47

called premature mortality and now I'm

play03:50

showing you the number of years lost in

play03:52

the world by caused by age and you can

play03:56

see the agenda of tackling premature

play03:59

death and children is still really large

play04:01

the big bars in the far left neonatal

play04:03

causes diarrhea pneumonia and malaria

play04:05

still important but you can also see in

play04:08

young adults the dark yellow

play04:09

that's HIV and tuberculosis you can see

play04:12

the dark purple those are road transport

play04:14

accidents and things like homicide and

play04:17

suicide show up is that salmon color

play04:19

there's a big agenda around young adult

play04:22

mortality as well but health is a lot

play04:26

more than simply avoiding death that's

play04:30

why we're so interested in wellness

play04:31

that's why in this study we look at over

play04:35

a thousand different outcomes and we put

play04:37

it all together and count up the number

play04:39

of years lost due to different diseases

play04:43

taking into account how severe they are

play04:45

and what's important here is the

play04:48

dollars on this diagram are different

play04:50

than the one I just showed you the ones

play04:52

that leap out are the light green which

play04:55

are mental disorders and substance abuse

play04:57

the light purple which are the

play04:59

musculoskeletal disorders and the darker

play05:02

purple are things like vision loss that

play05:04

we just heard about in hearing loss and

play05:06

congenital anomalies what ails you

play05:08

globally isn't actually what kills you

play05:11

and so when you put those two together

play05:13

you get a global view of all the

play05:17

complexity about health premature

play05:20

mortality and children from infectious

play05:21

diseases cancer and heart disease road

play05:24

traffic accidents HIV mental disorders

play05:27

but of course the world is not one

play05:29

homogeneous whole and part of the power

play05:32

of this tool is that you can now explore

play05:35

country by country what are the big

play05:38

causes and how they're changing so this

play05:41

view on the top is a square pie chart

play05:44

just like a pie chart the size of each

play05:46

box is proportionate to the problem and

play05:48

the non communicable diseases heart

play05:51

disease cancer musculoskeletal disorders

play05:54

mental disorders are in blue the

play05:56

communicable causes in red and injuries

play05:59

are in green and on the map on the

play06:01

bottom is the fraction of health loss in

play06:04

each country due to the communicable

play06:07

causes in West Africa in the country of

play06:11

leisure eighty percent of the burden of

play06:13

disease is from those communicable

play06:15

causes diarrhea pneumonia and malaria

play06:17

are particularly important in India a

play06:20

country in real transition about 45% is

play06:23

now non communicable disease forty five

play06:25

percent is the communicable diseases and

play06:27

the rest is injuries in China in 2010 it

play06:31

looks much more like the US where 80

play06:34

percent of the burden of disease is now

play06:35

from heart disease cancer mental

play06:37

disorders other non communicable causes

play06:40

but China has lessons to tell the rest

play06:43

of the developing world because if you

play06:44

go back to 1990 25 percent of the burden

play06:47

of disease in China was from

play06:49

communicable diseases they've been

play06:50

incredibly effective at tackling these

play06:53

causes particularly in children over the

play06:56

last two decades now if we go back to

play06:58

2010 in China and see that

play07:01

epidemiological shift

play07:02

in that country we can also drill down

play07:04

and show you the specific causes because

play07:07

of course health policy interventions

play07:09

clinical action requires specific

play07:11

disease information and so each of those

play07:14

boxes can be broken down into the 291

play07:17

diseases and the thousand plus outcomes

play07:19

but there's another way to see this

play07:21

information I'll keep on the theme of

play07:22

China and this is a ranked list

play07:26

people love ranked lists you know

play07:27

they're always in newspapers and so

play07:29

we've made a ranked list on the left is

play07:32

the ranked order of whatever outcome you

play07:34

care about in this case overall health

play07:35

loss in 1990 and on the right is the

play07:38

ranked list for 2010 and the causes are

play07:41

connected Reds or communicable causes

play07:44

blues or NCDs greens or injuries key

play07:47

story here is the big drops tuberculosis

play07:50

diarrhea pneumonia going down 80 percent

play07:52

in two decades in China and at the same

play07:55

time ischemic heart disease going up by

play07:57

almost 50% China has lessons to teach

play08:00

the developing world China has lessons

play08:02

to learn about how to manage ischemic

play08:04

heart disease from places like the US

play08:05

where we've brought ischemic heart

play08:07

disease down over time

play08:09

now disease and injury is not the whole

play08:12

story because health is a got some

play08:15

underlying determinants we think of them

play08:17

as risk factors things that you can

play08:19

modify in your own life but we can also

play08:21

think about modifying at the community

play08:22

level so the way to see that I'm going

play08:24

to show you the view in this tool for

play08:26

the u.s. is what are the leading risk

play08:29

factors and in this case the number one

play08:31

risk factor in the u.s. more than 14

play08:35

almost 14 percent of all health loss all

play08:37

years lost is diet

play08:40

followed by smoking followed by obesity

play08:43

and overweight followed by high blood

play08:47

pressure high blood sugar physical

play08:49

inactivity and alcohol the big dominant

play08:51

risks in the u.s. now there's a billion

play08:55

results and we could spend the rest of

play08:57

today and tomorrow and the rest of the

play08:58

week playing with these tools and I hope

play09:00

you do but what I want to do is tell you

play09:03

where this come from and what's the sort

play09:07

of central motivation behind it and so

play09:10

the story behind this tool starts

play09:12

actually 40 years ago it starts with my

play09:16

parents

play09:16

deciding to drag our family from

play09:19

suburban Minnesota by to Land Rover's in

play09:23

the UK drive across the Sahara and start

play09:26

and run a family as a hospital and so we

play09:29

all had jobs my father was a physician

play09:31

and I was the scrawny little kid here

play09:34

and my job was to set up the hospital

play09:37

pharmacy and run it and in that

play09:41

experience the ten-year-old and in

play09:43

subsequent places working for my parents

play09:45

in Africa I ended up with two questions

play09:47

that I'm still working on why are people

play09:51

so sick in some communities and what

play09:53

makes them so sick and how can we go

play09:56

beyond giving care to individuals to

play10:00

transforming the health of whole

play10:02

populations now when I finish college

play10:05

I got to start to address these

play10:07

questions head-on and there were two

play10:10

sources back in the late 80s early 90s

play10:12

one source was the media where you were

play10:16

simply inundated with a cacophony of the

play10:20

number one problem is this that or

play10:22

something else no way to get the big

play10:25

picture the other source was to go at

play10:28

the time to public health authorities

play10:29

and I did I went and added up all the

play10:32

claims about what people died from and

play10:34

it turned out that everybody in the

play10:36

world died three times over and I knew

play10:39

one thing was true that you can only die

play10:41

once now what that spawned is almost two

play10:46

and a half decades of an effort to get

play10:48

the four things together for us to

play10:51

really understand patterns of health

play10:53

around the world one is data data comes

play10:56

in lots of forms we think about

play10:58

digitized data these days but there's

play11:00

lots of data that looks like this

play11:01

that's handwritten down but the thing

play11:05

about figuring this out for patterns of

play11:07

health getting sort of real-time

play11:09

information on health over time is it's

play11:11

not like stock market prices where you

play11:13

just grab the price and deliver it to a

play11:15

laptop through some clever bit of

play11:18

technology there's actually an

play11:20

incredible bit of science behind

play11:22

figuring out all the biases that are in

play11:24

the data all the different case

play11:26

definitions different countries use the

play11:27

variation across places

play11:30

in how doctors assigned causes of death

play11:33

or make diagnoses so there's science

play11:36

there's data and there's also the

play11:38

evolution of a new cohort of data

play11:41

scientists here's some of ours with

play11:43

seeming superpowers at the Institute in

play11:45

Seattle but it's the idea that we have a

play11:48

new generation of people who have the

play11:51

skills to take raw data about health and

play11:54

turn it into information and the final

play11:56

transformation in developing this type

play11:59

of tool for everybody to use has been

play12:02

the recognition of the power of

play12:04

visualization here's a storyboarding

play12:07

that we did for one of the first

play12:08

visualizations namely how do you take

play12:11

such rich information and make it

play12:14

available to everyone why is this so

play12:19

important why am I so passionate about

play12:22

figuring out the answers to my two

play12:24

questions I think one way to see that is

play12:27

to look here in the US so on the top is

play12:31

life expectancy by county this for women

play12:34

it ranges from the counties in red to

play12:38

the counties in green by 12 years huge

play12:40

variation within the US and in fact in

play12:43

this little tool on our website you can

play12:45

ask the question what counties have a

play12:48

life expectancy like which country in

play12:51

the world so I'm going to highlight

play12:52

Libya and those are counties in the US

play12:55

where women's life expectancy is the

play12:57

same as in Libya today now the reason

play13:00

this is so important is that if we can

play13:02

understand what are the diseases and

play13:05

injuries and the risk factors that

play13:06

explain patterns of health in each place

play13:08

and we can learn from different

play13:10

community communities there's a huge

play13:13

potential to leapfrog and actually

play13:16

transform health of different

play13:17

populations so I want to leave you just

play13:20

with three thoughts first this tool

play13:26

allows us to ask questions that we

play13:29

didn't even know to ask before some of

play13:32

the Geographic patterns leap out at you

play13:33

new hypotheses second we can learn from

play13:38

success and failure all over the world

play13:40

there's lessons China can teach lessons

play13:43

China can learn lessons

play13:44

and third the one that we're most

play13:47

excited about is the power to engage

play13:50

everyone in seeking understanding about

play13:53

how to improve people's health because

play13:55

this is no longer the purview of the

play13:57

specialists this is in your hands thank

play13:59

you very much

Rate This

5.0 / 5 (0 votes)

Related Tags
Global HealthData VisualizationHealth SystemsSmart CitiesDisease BurdenMortality TrendsHealth InequalitiesRisk FactorsPublic HealthHealth Policy