Trisomy 9p is a rare genetic condition caused by extra genetic material from the short arm of chromosome 9. It is usually recognized before birth, at birth, or in early childhood because of a pattern of physical features, differences in growth, and developmental delay. Not everyone will have the same experience. Many people living with Trisomy 9p have lifelong learning and developmental needs, and some also have heart, feeding, or muscle tone problems that can affect daily life and, in more severe cases, overall health. Treatment for Trisomy 9p focuses on supportive care such as early intervention, physical and speech therapy, educational support, and treatment for specific medical problems.
How many people live with Trisomy 9p?
There is no reliable, up-to-date estimate of how many people are living with trisomy 9p worldwide or in the United States. It is considered extremely rare, but most published numbers come from individual case reports and small groups described in medical journals rather than full population counts, so experts do not have a dependable global or U.S. total.
Overview
Trisomy 9pSymptoms
Trisomy 9p often causes differences in facial features, development, and growth. Many children have low muscle tone, feeding trouble, and delays with speech or learning. Signs vary, and some also have heart, hand, or foot differences.
Outlook and prognosis
Outlook in Trisomy 9p varies widely. Many people need lifelong support for learning, speech, or movement, but with early therapies and treatment of heart or other birth differences, some live into adulthood.
Causes and risk factors
Trisomy 9p is caused by extra genetic material from the short arm of chromosome 9, usually from a new chromosome change and sometimes inherited from a parent with a balanced rearrangement. Risk is not linked to lifestyle or environmental exposures.
Genetic influences
Genetics are central to Trisomy 9p, because it is caused by extra genetic material from the short arm of chromosome 9. The amount and location of that extra material can affect how features and support needs vary from one person to another.
Diagnosis
Trisomy 9p is often first suspected from clinical features seen at birth or during childhood. The diagnosis of Trisomy 9p is confirmed with genetic tests, and imaging may help identify related physical differences.
Treatment and drugs
Treatment for Trisomy 9p focuses on day-to-day needs. Many benefit from early physical, speech, and learning support. Some also need treatment for heart defects, feeding problems, or hearing and vision issues.
Symptoms
Trisomy 9p can affect how a child grows, learns, communicates, and manages everyday tasks from an early age. For many people with Trisomy 9p, the mix of features is mild in some areas and more noticeable in others. The early features of Trisomy 9p often include delays in movement or speech along with differences in muscle tone, growth, or physical appearance. Some children also have medical problems such as heart or kidney differences, while others do not.
Many babies and children have muscles that feel less firm, so holding up the head, sitting, chewing, or keeping good posture can take more effort. This can make feeding and movement harder and may lead to tiring more easily.
Rolling, sitting, walking, and using the hands for everyday tasks may happen later than expected. Some children need physical or occupational therapy to build strength, balance, and coordination.
Speech often develops late, and some children use only a few words while others learn longer sentences over time. Learning can also be slower, so extra support at home and school is often helpful.
Some babies have trouble latching, sucking, or gaining weight, especially in the first months of life. Later on, children with Trisomy 9p may be shorter than average or grow more slowly than expected.
How people usually first notice Trisomy 9p?
How Trisomy 9p is first noticed often begins before or soon after birth: prenatal ultrasound may show growth differences or structural findings, and at delivery doctors may see a pattern of physical features such as a small head, low muscle tone, or distinctive facial features. As the first signs of Trisomy 9p become clearer in infancy, families and clinicians often notice feeding difficulties, slower developmental progress, and delays in sitting, walking, or speech. Not every child has the same features or the same degree of medical needs, but early recognition helps guide genetic testing, developmental support, and care planning.
Types of Trisomy 9p
No distinct types of Trisomy 9p are widely recognized.
Can I slow down the onset of symptoms?
No, there is no good evidence that lifestyle changes or medicines can meaningfully delay the start of trisomy 9p symptoms, because this condition is caused by extra genetic material and its effects usually begin before birth or in early childhood. Healthy habits can still support overall well-being, but they have not been shown to prevent or postpone the condition itself; what often helps most is early care such as physical, speech, and learning support, along with regular checkups to watch for concerns like growth, feeding, hearing, or heart problems. That will not stop trisomy 9p, but early support may help many living with it reach their best possible development.
What genetics can tell you about symptoms
In trisomy 9p, the extra genetic material on the short arm of chromosome 9 is closely linked to the pattern of symptoms, and in general, having more extra material tends to raise the chance of developmental delays, learning problems, differences in growth, and recognizable physical features. Genetics can also help explain why symptoms vary from one person to another, because the exact size of the duplicated segment and whether other chromosome changes are present can affect which features appear, how severe they are, and sometimes when they become noticeable. Even so, genetics cannot predict every detail of daily life, and two people with trisomy 9p can be affected quite differently.
Causes and risk factors
For many families, the first question is why Trisomy 9p happened. The main cause is extra genetic material from the short arm of chromosome 9. This usually happens by chance when the egg or sperm forms, or very early after conception. Sometimes Trisomy 9p is inherited from a parent who carries a balanced chromosome change and has no symptoms, which can raise the chance in another pregnancy. There are no known lifestyle or environmental causes of Trisomy 9p, and knowing your family history is a good first step.
What are the most common causes or risk factors?
Trisomy 9p is caused by having extra genetic material from the short arm of chromosome 9. In many cases, this happens by chance when the egg or sperm is made, but sometimes it is inherited from a parent who carries a balanced chromosome change, meaning their chromosomes are rearranged but they may have no symptoms themselves. The main known risk factor is a family history of this kind of chromosome rearrangement, and there are no well-established lifestyle or environmental causes.
Environmental and biological risk factors
Trisomy 9p usually is not linked to anything a parent did or did not do. Some risks are carried inside the body, others come from the world around us, but the known risk factors for Trisomy 9p are limited. In many cases, it starts with a chromosome change that happens by chance around the time of conception. That can make Trisomy 9p hard to predict or prevent.
Most cases begin with a random error when an egg or sperm cell forms, or very soon after fertilization. This biological event can create extra chromosome material without a clear outside trigger.
Sometimes the change happens during the first few cell divisions after conception. When that happens, there is usually no warning sign and no known action that could have prevented it.
No common environmental exposure has been clearly proven to cause Trisomy 9p. Routine day-to-day activities and most ordinary pregnancy exposures are not established causes.
Very strong chromosome-damaging exposures, such as high-dose ionizing radiation, can harm cells in general. Even so, this is not recognized as a usual or well-proven cause of Trisomy 9p.
Genetic risk factors
Families often want to know why Trisomy 9p happens and whether it could occur again. The genetic causes of Trisomy 9p involve extra material from the short arm of chromosome 9, either as a new chromosome change or through a rearrangement inherited from a parent. Some risk factors are inherited through our genes. The exact pattern can vary depending on how much extra 9p material is present and whether all or only some cells carry it.
Extra 9p material: The main cause of Trisomy 9p is an extra copy of part or all of the short arm of chromosome 9. That extra genetic material can change early development and lead to the features seen in Trisomy 9p.
New chromosome change: In many children, the chromosome change happens for the first time around conception and is not inherited from either parent. When this happens, the chance of it happening again is often low, though it is not always zero.
Parent rearrangement: Sometimes a parent carries a balanced chromosome rearrangement and is healthy because no genetic material is missing or extra. This can raise the chance of having a child with Trisomy 9p if extra 9p material is passed on in an unbalanced way.
Mosaic pattern: Some people have the extra chromosome material in only some of their cells instead of all of them. This can affect how the condition shows up, but it does not predict exactly how mild or severe features will be.
Segment size: The amount of extra 9p material can differ from one person to another. In general, larger duplicated segments may affect more genes and can be linked with a broader range of features, although there is still a lot of individual variation.
Lifestyle risk factors
Trisomy 9p is present from birth, so lifestyle habits do not cause it. Still, how lifestyle affects Trisomy 9p can be important for growth, strength, comfort, and day-to-day function. The most relevant lifestyle risk factors for Trisomy 9p are the habits that can worsen feeding problems, low muscle tone, poor sleep, constipation, and reduced mobility.
Inadequate calorie, protein, or fluid intake can worsen poor growth, fatigue, and feeding difficulties in people with Trisomy 9p. A feeding plan matched to chewing, swallowing, and sensory needs may help support weight gain and daily energy.
Too little movement can worsen low muscle tone, joint stiffness, poor balance, and delayed motor skills often seen in Trisomy 9p. Regular adapted activity and therapy-based exercises may improve strength, endurance, and participation in daily tasks.
Irregular sleep routines or poor sleep quality can worsen daytime irritability, attention problems, and developmental functioning in Trisomy 9p. A consistent sleep schedule and evaluation of snoring or frequent waking may help reduce these effects.
Low fiber intake, low fluid intake, and limited physical activity can increase constipation, which is common in many children with neurodevelopmental conditions including Trisomy 9p. Better bowel habits can improve comfort, appetite, and behavior.
Risk prevention
Trisomy 9p is a genetic condition present from birth, so in most families it cannot be prevented in the usual sense. Prevention usually means lowering the chance of complications, finding related health issues early, and supporting development over time. Different people need different prevention strategies—there’s no single formula.
If Trisomy 9p has affected your family, genetic counseling can help clarify whether the chromosome change happened by chance or could recur. This can guide pregnancy planning and decisions about testing before or during pregnancy.
Prenatal screening and diagnostic tests can sometimes detect Trisomy 9p during pregnancy, especially if there is a known family chromosome rearrangement. These tests do not prevent the condition, but they can help families prepare early for medical and developmental needs.
Regular follow-up with a pediatrician and the right specialists can help catch heart, kidney, feeding, hearing, or vision problems early. For many living with Trisomy 9p, this is one of the best ways to prevent complications of Trisomy 9p from building up silently.
Some children with Trisomy 9p have trouble sucking, swallowing, or gaining weight. Early feeding therapy and nutrition support can lower the risk of poor growth, dehydration, and chest infections from food or liquid going into the airway.
Can you prevent Trisomy 9p?
Usually, no, Trisomy 9p cannot be prevented, because it happens when a baby is born with extra genetic material from part of chromosome 9 and this is often not caused by anything the parents did or did not do. In some families, it is linked to a chromosome change carried by a parent, so genetic counseling before or during pregnancy may help explain the chance of it happening again. Even then, counseling can help with planning and testing, but it cannot fully prevent the condition.
Transmission
Trisomy 9p is not infectious, so it does not spread from person to person through contact, the air, sex, or blood. For many families, the genetic transmission of Trisomy 9p starts as a new chromosome change around the time of conception, meaning it happened by chance and was not caused by anything a parent did.
Less often, Trisomy 9p can be passed down if a parent carries a balanced chromosome rearrangement, where the genetic material is present but arranged differently. When that happens, the chance of another pregnancy being affected can be higher, so genetic testing and counseling can help explain how Trisomy 9p is inherited in your family.
When to test your genes
If Trisomy 9p is suspected because of developmental delays, differences seen at birth, or a family history of a chromosome rearrangement, genetic testing should be done as early as possible. Testing confirms the diagnosis and helps guide medical monitoring, early therapies, and family planning.
Diagnosis
Many people with Trisomy 9p are diagnosed because a doctor notices a pattern of growth, developmental, and physical features that seem to fit together rather than pointing to one isolated problem. The diagnosis of Trisomy 9p is usually confirmed with chromosome testing, which looks for extra genetic material from the short arm of chromosome 9. Getting a diagnosis is often a turning point toward answers and support.
Doctors begin by looking at a child’s growth, muscle tone, development, and physical features, including the head, face, hands, and feet. No single feature proves Trisomy 9p, but the overall pattern can raise strong suspicion.
A detailed family and pregnancy history can help doctors understand whether the chromosome change is likely to be new or inherited from a parent with a balanced chromosome rearrangement. This also helps guide which family members may need testing.
The main test is a chromosome study, often done from a blood sample, to look for extra material from chromosome 9p. This is the key step in the genetic diagnosis of Trisomy 9p.
Chromosomal microarray can show the extra genetic material in more detail and may help define how much of 9p is involved. This can be useful when features are suggestive but a standard test does not give the full picture.
How is Trisomy 9p diagnosed?
Trisomy 9p is usually suspected when a doctor sees a pattern of growth, learning, and physical features that fit the condition, often after a physical exam and a review of a child’s development. The diagnosis is confirmed with chromosome testing, which looks at the body’s genetic material and shows extra material from part of chromosome 9. During pregnancy, an ultrasound may first raise concern, but confirmation usually comes from testing cells from the placenta or amniotic fluid.
Stages of Trisomy 9p
Trisomy 9p does not have defined progression stages. This is because it is a genetic condition present from birth, and its effects usually reflect a person’s underlying chromosome pattern rather than a disease that moves through set phases over time. Doctors usually start with a conversation about development, learning, growth, and any birth differences, then confirm the diagnosis with chromosome testing. Ongoing follow-up focuses on the signs and symptoms of trisomy 9p, such as development, speech, hearing, heart health, and growth, since these can vary widely from one person to another.
Outlook and prognosis
Outlook in trisomy 9p varies widely and depends on how much extra chromosome 9p material is present and whether there are associated heart, brain, feeding, or airway problems. Many affected children survive into adolescence and adulthood, especially when the duplication is isolated and major internal malformations are absent, but most have lifelong developmental delay and varying degrees of intellectual disability that require ongoing support. Medical complications such as congenital heart defects, seizures, recurrent respiratory infections, feeding difficulties, and scoliosis can have a major impact on function and quality of life. Published data are limited because the condition is rare, so precise life-expectancy estimates are not available. Mortality is generally related to the severity of associated birth defects and complications in infancy or early childhood rather than to the chromosome change alone. Early multidisciplinary care, including cardiology, neurology, nutrition, developmental therapies, and orthopedic monitoring, can improve overall outcomes and reduce preventable complications.
Long-term effects
Many living with Trisomy 9p have long-term effects that touch development, learning, growth, and day-to-day health. The picture can vary a lot from one person to another, depending on how much extra genetic material is present and what body systems are affected. Long-term effects vary widely, and some people have milder challenges while others need lifelong medical and developmental support. In childhood and adulthood alike, the most important long-term concerns usually involve intellectual disability, speech and motor delays, and related health problems that may persist over time.
Delays in sitting, walking, speaking, and learning often continue over the long term in Trisomy 9p. Many people need ongoing support with communication, school skills, daily tasks, or independent living as they get older.
Low muscle tone can affect posture, balance, and coordination from infancy onward. For many, this can mean slower motor progress, tiring more easily, or needing extra help with fine motor tasks such as dressing or writing.
Some people with Trisomy 9p remain shorter than expected for their family and may have slower overall growth. Feeding difficulties early in life can add to this, especially in children who have trouble gaining weight.
Speech and language differences are often a major long-term feature, and some people speak only a few words while others use short phrases or alternative ways to communicate. Early symptoms of Trisomy 9p often include delayed babbling or slow language development, and these differences may continue into adult life.
How is it to live with Trisomy 9p?
Living with trisomy 9p can look very different from one person to the next, but for many it means growing and learning more slowly, needing extra support with speech, movement, school, and daily routines. Some people with trisomy 9p also have medical needs, such as help with feeding, muscle tone, hearing, or heart and other body differences, so daily life may include therapy visits and regular checkups alongside family life. For parents, siblings, and other caregivers, this can bring added planning, advocacy, and emotional strain, but it also often leads to close routines, strong support networks, and a deep understanding of the person’s unique strengths.
Treatment and drugs
Treatment for Trisomy 9p focuses on the health and developmental needs each person has, since there is no single medicine that corrects the chromosome change itself. Many living with Trisomy 9p may need care from several specialists, with treatment aimed at issues such as feeding problems, low muscle tone, heart differences, seizures, hearing or vision concerns, and delays in speech, learning, or movement. Treatment plans often combine several approaches, including therapies like physical, occupational, and speech therapy, special education support, and medicines or surgery when specific medical problems need them. Not every treatment works the same way for every person, and care often changes over time as a child grows and new needs become clearer. Supportive care can make a real difference in how you feel day to day, and regular follow-up helps families and doctors adjust the plan to improve comfort, safety, and daily function.
Can you cure Trisomy 9p?
No, trisomy 9p cannot be cured because it is a genetic condition present from birth. Treatment focuses on helping with the specific problems it causes, which may include early support with learning, speech, movement, and feeding, along with regular medical care for any heart, growth, or other health concerns. For many families, this care can improve comfort, development, and day-to-day life, even though it does not remove the condition itself.
Non-drug treatment
Daily life with Trisomy 9p often involves support for movement, speech, learning, and feeding rather than one single treatment. Supportive therapies can help children and adults build skills, stay comfortable, and take part more fully at home, school, and in the community. Because Trisomy 9p affects people differently, care is usually tailored to each person’s strengths and needs. For many families, the best plan starts early and is adjusted over time.
Early therapy services in infancy and the preschool years can support motor, communication, and social development. This can be especially helpful when early symptoms of Trisomy 9p include low muscle tone or delayed milestones.
Physical therapy can help with balance, strength, posture, and walking. For many, this can mean easier movement during everyday tasks like climbing stairs, getting dressed, or keeping up on the playground.
Occupational therapy focuses on hand use, daily skills, and sensory challenges. Many living with Trisomy 9p may use it to improve feeding, writing, dressing, and other routine activities.
Speech and language therapy can help with talking, understanding language, and social communication. If speech is very limited, therapists may also suggest communication aids such as picture systems or speech devices.
Your genes may have an impact on how drugs work for you
Trisomy 9p itself does not usually tell doctors which medicine will work best, but people with trisomy 9p can still respond differently to medicines often used for related health issues, such as seizures, reflux, sleep problems, or behavior concerns. For many, this simply means one medicine may help a lot, while another may cause more side effects or need a different dose, so careful follow-up matters. Testing genes to predict drug response is not a routine part of care for trisomy 9p, but doctors may think about it if a medicine is not working as expected or is causing unusual side effects.
Pharmacological treatments
There is no medicine that can change the extra genetic material in Trisomy 9p, so treatment is aimed at specific symptoms and health problems. Many living with Trisomy 9p may use medicines for seizures, reflux, constipation, attention or behavior concerns, sleep problems, or other issues that come up over time. Not everyone responds to the same medication in the same way. Doctors usually choose drugs based on the person’s symptoms, age, and any heart, kidney, or feeding concerns.
If Trisomy 9p causes seizures, doctors may use anti-seizure drugs such as levetiracetam, valproate, lamotrigine, or oxcarbazepine. The choice depends on the seizure type, age, and side effect profile. For many families, finding the right medications for seizures in Trisomy 9p may take some adjustment over time.
Some people with Trisomy 9p need medicines for acid reflux, such as omeprazole, lansoprazole, or famotidine. These drugs can help with pain after feeds, frequent spit-up, coughing, or poor weight gain linked to reflux.
Constipation is often treated with medicines such as polyethylene glycol, lactulose, or senna when bowel habits are difficult to manage with fluids and diet alone. Regular treatment can make eating, sleep, and daily comfort easier.
If attention problems, impulsivity, irritability, or severe agitation are affecting daily life, doctors may consider medicines such as methylphenidate, guanfacine, clonidine, or sometimes risperidone or aripiprazole. These are used carefully and only for specific symptoms, not for Trisomy 9p itself.
Genetic influences
For people living with Trisomy 9p, the genetic cause is known: there is extra genetic material from the short arm of chromosome 9, usually because that segment is present in three copies instead of the usual two. This extra material can change development before birth, which is why Trisomy 9p may affect growth, learning, muscle tone, and appearance. In many families, the chromosome change happens for the first time in the child, but sometimes it is inherited because a parent carries a balanced chromosome rearrangement and has no symptoms themselves. Family history is one of the strongest clues to a genetic influence. Even so, most parents did nothing to cause Trisomy 9p, and genetic testing can help show whether the extra chromosome piece was new or passed down through the family. That result can help explain recurrence risk and guide genetic counseling for future pregnancies.
Is Trisomy 9p genetic?
Genetics are central to Trisomy 9p, because it is caused by extra genetic material from the short arm of chromosome 9. The amount and location of that extra material can affect how features and support needs vary from one person to another.
Having a genetic risk is not necessarily a diagnosis
Changes in genes are a normal part of human biology and are common across the general population. Most of these variants do not directly affect health and simply reflect natural human diversity. For many genes, having a variant connected with a condition suggests a possible link rather than a definite diagnosis, especially when several genes and environmental factors are involved. In some cases, though, a single well-characterized variant in a particular gene can be enough to confirm a diagnosis.
Pharmacogenetics—how genetics influence drug effects
Treatment is usually shaped by the specific health problems the extra genetic material causes, rather than by Trisomy 9p itself having one standard medicine. For many living with Trisomy 9p, this can mean one child needs medicine for seizures or reflux, while another may mainly need support for feeding, muscle tone, heart issues, or development. Genetics is only one factor, so doctors also look closely at age, growth, other medical conditions, and how someone is responding day to day.
There is no drug that fixes the chromosome change in Trisomy 9p, so care focuses on treating symptoms and preventing complications. In practice, the medications used in Trisomy 9p depend on the person’s needs, and doses are usually adjusted carefully because feeding difficulties, low muscle tone, or organ problems can change how well medicines are tolerated. Researchers do not have strong evidence that Trisomy 9p causes one predictable pattern of drug response across all medicines, so the best treatment for Trisomy 9p symptoms is usually individualized and reviewed over time.
Interactions with other conditions
For many living with Trisomy 9p, health needs do not come from the chromosome change alone but from the other problems that can go with it, such as heart defects, feeding difficulties, hearing or vision problems, and kidney or urinary tract differences. Many people live with more than one health issue at a time. In everyday life, that can mean a baby tires easily during feeds because both low muscle tone and a heart problem are present, or a child’s speech delay is harder to sort out when hearing loss is also affecting communication. People with Trisomy 9p may also be more vulnerable to repeated chest infections if poor muscle tone, reflux, or trouble swallowing leads to food or liquid going down the wrong way. Developmental and learning challenges can overlap with sleep problems, seizures in some cases, or behavioral conditions, which may change what the early symptoms of Trisomy 9p look like from one child to another. Because the pattern is so variable, doctors usually watch the whole picture over time and may involve several specialists so related conditions are found and treated early.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
What other conditions can cause similar symptoms to Trisomy 9p?
Trisomy 9p can look similar to other chromosome conditions, especially Down syndrome and the more severe trisomy 13 and trisomy 18, because all can cause delayed development, low muscle tone, growth problems, and differences in the face, hands, heart, or other parts of the body. Doctors may also consider other rare conditions caused by extra or missing pieces of chromosomes, and genetic testing is usually what helps tell them apart.
History
For many living with Trisomy 9p, the condition is part of a much longer medical story than it may seem at first glance. Doctors began recognizing a repeated pattern of developmental differences and physical features in the second half of the 20th century, when chromosome testing became more widely available. Before that, children and adults with Trisomy 9p may have had similar needs, but the reason behind them was often unclear.
In recent decades, awareness has grown as specialists learned that having extra material from the short arm of chromosome 9 can affect growth, learning, muscle tone, and appearance in ways that vary from one person to another. Early reports came from careful descriptions of babies and children who shared certain features, such as delays in reaching milestones or differences in facial development. As testing improved, doctors were better able to tell Trisomy 9p apart from other chromosome conditions that can look similar in early childhood.
That shift mattered in everyday life. A family might once have been told only that their child had “developmental delay” without a clear explanation, while later families were more likely to get a specific diagnosis and more tailored support. Over time, researchers also learned that Trisomy 9p is not exactly the same in everyone, which helped explain why symptoms can range from mild to more significant.
The history of Trisomy 9p is also closely tied to advances in chromosome analysis. Earlier methods could identify only larger chromosome changes, but newer laboratory tools allowed smaller changes to be seen more clearly. This helped doctors confirm the diagnosis earlier, sometimes even before birth, and gave families better information about what kinds of medical checks and developmental support might help.
Today, the history of Trisomy 9p is still being written. What began as a handful of case descriptions has grown into a clearer picture of a rare chromosome condition with a broad range of effects. That growing knowledge has made it easier to recognize early symptoms of Trisomy 9p, connect families with services, and improve care over time.