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spinal muscular atrophy in canada: stats and impact on patients, caregivers and quality of life
spinal muscular atrophy (sma) is a rare genetic disease affecting less than 300 canadians per year.
it is estimated that sma caregivers and patients spend an average of $12,800 on home modifications and $4,500 on assistive devices in a year in canada.
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spinal muscular atrophy, or sma, is a genetic disease driven by the loss of motor neurons in the spinal cord. there are five main types of sma, each with its own progression and life expectancy. the most common type, type 1, accounts for 50 per cent of all sma cases.
globally, sma has an incidence rate of 1 to 2 per 100,000 people. in canada, the numbers are slightly higher than the global average. according to the canadian neuromuscular disease registry (cndr), 5.53 per 100,000 people develop sma, whereas the canadian paediatric surveillance program (cpsp) puts that number closer to 3.34 per 100,000 persons.
according to johns hopkins medicine, sma is “one of the most prevalent genetic disorders affecting young children and a major cause of death in infancy.”
what is spinal muscular atrophy?
sma is a genetic disease that occurs when a specific protein needed by neurons, known as survival motor neuron (smn), is not produced enough in the body due to mutations in the smn1 gene. without adequate smn protein, motor neurons cannot perform as they should, leading to their death and a lack of cell signalling to the muscles.
children receive one copy of the smn1 gene from each parent. for sma to develop, both those genes must be mutated when passed down to the child. if only one is, the child is unlikely to develop sma. however, they become carriers of the mutated gene and can pass it down to their children.
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the typical symptoms associated with sma include:
- weakness in the muscles that control movement leading to immobility
- difficulty breathing
- trouble with swallowing
there are five main types of sma, each with different onset ages, severities, and symptoms. they include:
- type 0: this is a rare form of sma that affects infants in the womb. children who develop type 0 often live for a few months or less following birth due to extreme weakness and difficulty breathing on their own.
- type 1: otherwise known as werdnig-hoffmann disease, type 1 sma affects newborn infants and babies up to 6 months old. typically, most infants with type 1 start to show symptoms of sma around the third month of life, such as difficulty breathing, moving, and eating. it is severe, and if treatment is not sought quickly, it is unlikely that these newborns will live past the age of 2.
- type 2: type 2 sma is moderate to severe and typically develops when a child is between six and 18 months old. babies with this type have weak muscles and are unable to walk.
- type 3: otherwise known as kugelberg-welander syndrome, type 3 sma starts as early as 18 months but can take until adolescence to develop. children with this mild form of sma can walk on their own but may often experience falls due to leg and arm weakness.
- type 4: the slowest type to develop, type 4, has an age of onset of 35 or older. it starts slowly and worsens over time.
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type 1 accounts for roughly 50 per cent of all sma cases and comes with a life expectancy of 2 or fewer years. the other types have their own severity levels and, because of that, varying life expectancies.
- type 0: a few months after birth
- type 2: roughly 70 per cent of those with type 2 sma live to 25 or older.
- type 3: life expectancy is not altered in type 3, but many with this type will deal with physical disabilities.
- type 4: life expectancy is not changed in type 4, with people affected having the same life span as those without sma.
because of the way sma affects the body, it can lead to complications, including:
- scoliosis
- breathing in fluid or food into the airways
- stiff and deformed joints
- bone fractures caused by fragile bones
the time in which a person with sma starts treatment can play a significant role in their life expectancy, with those starting therapy before the age of 2 having the best outcomes.
current sma statistics in canada
the number of people living with sma in canada can be divided into age groups. according to cndr data from 2022, the total number of sma cases was 299 that year.
the age group with the highest number of sma cases is those between 10-14 years of age, with 45 total cases. other cases by age group include:
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- 0-4: 40
- 5-9: 38
- 15-19: 37
- 20-24: 29
- 25-29: 30
- 30-34: 9
- 35-39: 21
- 40-44: 7
- 45-49: 10
- 50-54: 8
- 55-59: 5
- 60-64: 9
- 65-79: 9
males are more likely to be affected than females, but not by a large number. the same data from the cndr found that out of the 299 cases in 2022, 154 were found in males and 139 in females.
the number of people per type is also highlighted in the data, with the exception of type 0:
- type 1: 59 cases, accounting for 19.7 per cent of total cases
- type 2: 126 cases, accounting for 42.1 per cent of total cases
- type 3: 103 cases, accounting for 34.4 per cent of total cases
- type 4: 5 cases or less. type 4 cases, and those of unknown type, account for the remaining 3.8 per cent.
the average age of sma onset is 12 years old, but that also varies by type because each is characterized by its age of onset.
impact of sma on patients and caregivers
the overall impact of sma on canada isn’t well documented. that said, there is data surrounding how the disease affects patients with the disease as well as their caregivers.
while much of the care given to people with sma is covered by provincial health plans, 70 per cent to be exact, the other 30 per cent becomes an out-of-pocket expense. according to the canadian institute for health information, the average caregiver or person with sma pays $973 for sma care per year.
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the direct and indirect costs associated with sma are not well documented, but they are thought to be much higher than the average canadian has to pay for healthcare. the direct and indirect costs can include:
- hospital visits
- medications
- home modifications
- rehabilitation
- time spent caregiving
- loss of productivity to society because of inability to work or premature death
according to a recent study outlining the impact sma has on patients and caregivers in canada, data to support the actual cost of healthcare for sma is lacking. however, the study did detail how many patients used the healthcare system in the past year, with 96.8 per cent reporting at least one outpatient visit.
the same study outlines caregiver and patient costs, with an average of $12,800 spent on home modifications, $4,500 on assistive devices, $1,200 on travel and accommodations, and $6,800 on other professional health services to help manage the disease.
impact of sma on quality of life
due to the nature of the disease, people with sma have a negatively impacted quality of life. according to research, people with type 1 have the lowest quality of life with worse mobility scores and an increase in pain and discomfort caused by sma due to factors such as the inability to walk, wash, or dress themselves.
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anxiety and depression are also prevalent in those with type 1 sma, as it can cause the inability for people to do usual activities that others in their age group can do.
people with type 3 sma have the highest quality of life scores, but they still contend with symptoms that drive a lower quality of life than the average canadian without sma.
the future of sma in canada
while the future of sma in canada is unclear due to the lack of clinical research surrounding the impact of the disease on canadians, there is some hope for better screening practices that could help amplify research and improve the lives of those who have the mutated smn1 gene.
according to the neuromuscular disease network for canada (nmd4c), only 72 per cent of newborns are screened for sma at birth through the nbs program, designed to screen newborns for genetic disorders at birth. all provinces are part of the nbs program, but not all use it to screen for sma.
because of that, these screening practices for sma are only done in some provinces. research shows that new brunswick, nova scotia, newfoundland, quebec, and prince edward island fail to use the nbs to screen for sma.
the nmd4c report indicated that these provinces are working toward adding sma to their nbs program, though they still have yet to do so.
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screening practices are a great way to diagnose sma early on in life, giving newborns and those who develop the disease a better chance at survival because when treatment is sought early, outcomes are better.
the nmd4c is dedicated to improving research and care for those living with neuromuscular disease. their work with sma will hopefully change the course of disease for those who will be born with it in the future.
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