Written by Ada’s Medical Knowledge Team
What is osteoporosis?
Osteoporosis is a disorder of the skeleton in which the structure of the bones becomes porous. This can lead to the bones becoming weak, fragile and prone to painful fractures (breaks). It is a common bone disorder which can affect people of all ages. According to the National Institutes of Health, over 53 million people in the U.S. are affected by or are at high risk of osteoporosis developing due to having low bone mass.
Bones are composed of protein, collagen and calcium. In healthy bones, these elements combine to ensure that the bones have a strong structure. In people with osteoporosis, however, the density of the bones decreases. This causes the structure of the bones to weaken in a process which can worsen over time.
Changes to the bones which occur when a person is affected by osteoporosis include:
- Bone density decreases (loss of calcification)
- Bones become porous and spongy
- Gaps develop in the bone structure
- The sturdiness, typical of healthy bones, is lost
- Fractures may occur independently, or as a result of very minor knocks or falls.
Osteoporosis can remain undetected for many years, as it does not usually cause noticeable symptoms.
For most people, the first sign of osteoporosis is the diagnosis of a painful bone fracture resulting from a minor injury, such as a trivial slip-and-fall accident (an outcome which would not be expected to occur in someone with healthy bones).
People with osteoporosis are also prone to stress fractures, where a break occurs during a prolonged bout of a normal activity, such as walking, with no direct causal injury.
Other signs that a person might be affected by osteoporosis include:
- Pain in the spine and back; spinal fractures can cause long-term or chronic pain
- Hyperkyphosis; a stooped posture, often characterised by a hunched back
- Diminishing height
When a fracture occurs, the break will be accompanied by intense pain at the site of the fracture, which radiates out and also affects the surrounding area.
- Femoral neck (hip)
- Tibiofemoral joint (knee)
- Vertebrae (spine)
- Lumbar region (the lower part of the spine, which joins the torso to the abdomen)
- Thorax (chest)
Bone density increases until a person reaches their early 20s. Generally speaking, from a person's mid-30s, bone density begins to decrease. Osteoporosis is caused when their bone density decreases at a rate which compromises the structure of their bones, which in turn become brittle (easily broken) and spongy.
Why does bone density decrease over time?
All bones perform a constant process of remodelling throughout a person’s lifetime. This involves the older bone matter dissolving (a process called resorption) at the same time as new bone cells produce new bone matter (osteoid).
According to the International Osteoporosis Foundation, the principal reason that the bones weaken in people with osteoporosis is that the processes involved in remoddelling are occuring out of sync with one another. Old bone matter is dissolved at a significantly faster rate than new bone matter is produced, leading to gaps forming in the structure of the bones and an overall decrease in bone density.
Causes of osteoporosis in children
Osteoporosis in children is uncommon, because bones generally grow stronger throughout one’s childhood and young adulthood, and the loss of bone density usually begins in adulthood.
Likewise, hormonal changes and health problems linked to osteoporosis, predominantly tend to affect older adults. However, it is possible to be affected by osteoporosis at any age, and there are certain conditions which increase a child’s likelihood of experiencing the condition.
Primary osteoporosis in children
Certain genetic conditions which impede the development of healthy bones can cause osteoporosis in children. These include:
- Osteogenesis imperfecta (OI)
- Osteoporosis pseudoglioma syndrome
These conditions cause osteoporosis in children by inhibiting the development of healthy bones.
Idiopathic juvenile osteoporosis is a rare condition in which a previously healthy child or teenager develops osteoporosis. If you are concerned that your child, or a child that you know, may be showing signs of osteoporosis, get a free symptom assessment with the Ada app.
Secondary osteoporosis in children
It is much more common for children, who are affected by osteoporosis, to contract the condition as a result of other medical conditions and/or the medications associated with their management, such as the steroid medications often prescribed for children with asthma, eczema and arthritis.
Conditions which increase the likelihood of developing osteoporosis in children include:
- Problems related to sex hormone production. Children who experience delayed puberty are at increased risk of experiencing problems with bone growth and maintenance.
- Inflammatory conditions. Bone loss is linked to inflammatory diseases, and osteoporosis is therefore more likely to be experienced by those with conditions like childhood arthritis and Crohn's disease.
- Gastrointestinal diseases. Conditions like coeliac disease impede the intake of nutrients, including those needed for the maintenance of healthy bones.
- Eating disorders. Anorexia nervosa and bulimia impede nutritional intake and engender hormonal imbalance, which negatively impacts bone formation.
- Conditions which compromise a child’s ability to be active. These include muscular dystrophy, spinal cord injury and cerebral palsy.
Risk factors for developing osteoporosis
Factors which make it more likely that someone will develop osteoporosis include:
Having a small frame
In general, people with a smaller frame have thinner, smaller bones, which can deteriorate to the point of being affected by osteoporosis more rapidly than larger, thicker bones.
According to the National Osteoporosis Foundation, of the estimated 10 million Americans with osteoporosis, about eight million or 80% are women. The two principal reasons why osteoporosis disproportionately affects women are that they tend to have smaller, thinner frames than men, and that their hormone levels change during menopause, with a drop in estrogen levels causing bone loss.
Osteoporosis is particularly prevalent amongst postmenopausal women. Approximately 200 million women worldwide are estimated to be affected. After menopause, the levels of estrogen in the female body drop significantly, which affects the body’s ability to maintain healthy bones. For this reason, the removal of one’s ovaries causes a decrease in estrogen levels and is, therefore, also a risk factor for osteoporosis.
Having low testosterone levels
In men, a decrease in hormone levels can precipitate the onset of osteoporosis, although not as commonly as in women. Conditions which cause one’s testosterone levels to diminish (such as hypogonadism), the long term use of steroid medications and regular alcohol consumption can all lower testosterone levels in men, thus increasing the likelihood of being affected by osteoporosis.
Having a family history of osteoporosis
An increasing body of research supports the hypothesis that osteoporosis is a hereditary condition. People, whose parents have been affected by osteoporosis, are considered to be particularly likely to develop the condition themselves.
Taking steroid medication for over three months
Steroid medications significantly compromise the body’s ability to metabolise calcium and vitamin D. Both of these are essential for the maintenance of healthy bones.
Having calcium deficiency
The sturdiness and strength of one’s bones and teeth is dependent on the maintenance of their calcium content. Ninety-nine percent of the calcium within the body is stored in one’s bones and teeth.
However, the body also relies on calcium for the effective functioning of certain processes, including muscle contraction, blood clotting and the maintenance of a normal heart rhythm. When the overall levels of calcium within the body are depleted, the calcium stored in the bones is extracted by the body for use in these processes. This depletion of calcium from the bones causes gaps in their structure which will eventually lead to osteoporosis.
Having vitamin D deficiency
Having adequate levels of vitamin D in one’s body is essential in order for the calcium, gained from one’s diet, to be absorbed effectively by the body. People with vitamin D deficiency are less likely to absorb the calcium they need in order to maintain healthy bones, which puts their bones at increased risk of osteoporosis.
Having an eating disorder
Conditions like bulimia and anorexia nervosa involve severely restricting one’s dietary intake in order to lose weight. This results in malnutrition and hormonal changes within the body, both of which precipitate a loss in bone density, increasing the likelihood of osteoporosis.
Being physically inactive
Being active, particularly in young adulthood, is linked to cultivating higher bone mass and stronger bones, which are better able to withstand the process of aging over time.
Having hyperparathyroidism (parathyroid disease)
In healthy bodies, the parathyroid hormone is produced in appropriate quantities in order to regulate the distribution of calcium within the body. People with hyperparathyroidism produce excessive levels of the parathyroid hormone in their bodies. When this happens, calcium is removed from the bones at a faster rate than is healthy, causing osteoporosis.
Having rheumatoid arthritis
The chronic inflammation caused by rheumatoid arthritis results in bone loss. This is the primary cause of osteoporosis in people who are affected by rheumatoid arthritis (RA). RA is a condition which also causes immobility and physical disability, thus reducing an individual’s ability to be physically active – a key means of preventing osteoporosis. RA is also widely associated with high-dose corticosteroid use. These medications compromise the body’s ability to metabolise calcium and vitamin D, essential for healthy bones; this can lead to the development of osteoporosis.
Having gastrointestinal problems
Problems, such as inflammatory bowel disease and coeliac disease, can heighten one’s risk of developing osteoporosis by compromising the body’s ability to absorb vitamins and minerals from one’s diet, including the intake of calcium and vitamin D which are necessary for the maintenance of healthy bones. Feeling unwell? Get a free symptom assessment with the Ada app.
Using tobacco products regularly
According to the World Health Organization, in those who use tobacco products, bone density decreases at a faster rate than the bone density ofthose who do not. By the time a person who smokes regularly reaches old age, this decrease in bone density is significant enough to correlate to weaker bones, and a greater likelihood of fractures.
Drinking alcohol excessively
People who drink alcohol regularly and/or excessively are at greater risk of developing osteoporosis than those who do not, particularly those who do so in their teenage years and young adulthood. Ethanol has been found to reduce bone formation, leading to weaker bones which become increasingly prone to fracturing in later life.
The first sign of osteoporosis in most people is a fracture, which usually occurs as the result of a trivial slip-and-fall accident or in the course of one’s daily activities. People who visit the doctor with a fracture and/or are at high risk of osteoporosis are often recommended to undergo a bone density scan in order to diagnose and begin treating causes of osteoporosis.
DEXA bone density scan
When a doctor examines a fracture, they will also order a bone density scan if they consider it likely that the fracture has occurred as a result of osteoporosis. Bone density scans measure one’s bone mineral density (BMD). The technology used in a bone density scan is called dual-energy x-ray absorptiometry (DXA or DEXA) or bone densitometry.
Bone density scans are performed to:
- Diagnose osteoporosis
- Determine how advanced the condition is
- Identify appropriate treatment options
A bone density scan measures the amount of x-rays which are being absorbed by one’s bones and calculates a T score and a Z score.
A T score* is a rating of one’s bone density in comparison to a healthy 30-year-old. The lower a person’s T-score, the lower their bone density. Healthy bones achieve a rating of -1 and above. If one’s rating is -2.5 and below, it is likely that one is affected by osteoporosis.
According to the World Health Organization (WHO):
- A T-score of -1.0 or above means a person has normal bone density (for example, 0.9, 0 or -0.9)
- A T-score between -1.0 and -2.5 usually means a person has low bone density or osteopenia (for examples, T-scores of -1.1, -1.6 or -2.4)
- A T-score of -2.5 or below will usually result in a diagnosis of osteoporosis (for example, T-scores of -2.6, -3.3 and -3.9)
A Z score reflects the number of standard deviations above or below what is a normal score for someone of one’s age, weight, ethnicity and sex. A Z-score above -2.0 is normal according to the International Society for Clinical Densitometry (ISCD). The Z score is crucial to diagnosing osteoporosis, because an excessively high or low score can indicate the possible presence of other conditions which are precipitating one’s decreased bone density.
Assessing fractures for osteoporosis
The procedures which are used to examine bone fractures can often provide additional information which is helpful in diagnosing osteoporosis.
Procedures which are commonly used to examine fractures resulting from osteoporosis include:
- CT scan of the spine. A version of computer tomography (CT) scanning called quantitative CT (QCT) can be used to measure bone density and determine the likelihood of spinal fractures. CT scanning is also used in the event of spinal fractures occurring in order to assess the damage and the alignment of the spine.
- MRI scan of the spine. Magnetic resonance imaging can be used to assess fractures for the presence of additional diseases such as cancer – helping rule out a diagnosis which is not of osteoporosis – and to determine how long ago a given fracture occurred.
- Bone X-ray. X-rays are often used to examine the fractures caused by osteoporosis, as they can be used anywhere on the body to provide accurate images of breakages in bones.
Treatment for osteoporosis
Treatment for osteoporosis focuses on four main areas:
- Healing fractures
- Ensuring that one’s nutritional intake contains appropriate quantities of vitamin D and calcium, often by incorporating supplements into one’s diet
- Taking medication to strengthen one’s bones
- Preventing future falls and fractures
Osteoporosis does not cause broken bones to heal any more slowly than they otherwise would. Broken bones take between six and eight weeks to heal on average, but some fractures may require additional intervention.
Fractures which commonly occur as a result of osteoporosis and which may require additional intervention include:
- Hip fractures; a hip replacement is often needed
- Wrist fracture; an operation is often needed
- Spinal fracture; surgery and/or physiotherapy may be needed to correct the alignment of the spine
Lacking sufficient levels of calcium and vitamin D is a primary risk factor for developing osteoporosis. The body cannot make calcium on its own, and the production of sufficient levels of vitamin D (which the body needs in order to absorb calcium from food) requires exposure to plenty of sun. It is vital that one’s diet contains sufficient sources of both nutrients. People with osteoporosis are often advised to take supplements of both vitamin D and calcium in order to replenish the body’s levels of these substances and prevent further bone damage.
One’s doctor will advise on the appropriate brands and strengths of supplements to take, depending on factors including one’s age, weight, gender and the severity of one’s condition.
Medication for osteoporosis
There are many different types and brands of medication for osteoporosis. The kind of medication, which is recommended for an individual, will be selected based on factors including:
- Hormonal levels
- Ability to adhere to a given dosing schedule
Bisphosphonates (oral medications)
The most commonly prescribed type of medications for osteoporosis are bisphosphonates. These are oral medications which work to maintain one’s bone density and delay the process of the bones breaking down. However, bisphosphonates may not be suitable in all cases of osteoporosis, as they can carry side effects of severe stomach upsets and heartburn (which can be lessened in most cases by taking the medication according to precise guidelines).
People who cannot tolerate oral bisphosphonates due to digestive complications and/or the extent to which their health is compromised by osteoporosis and other possible coexisting conditions may be prescribed injected medications.
- Denosumab (Prolia / Xgeva). This is a new medication suitable for both genders, which is unrelated to bisphosphonates and may be a viable alternative for people who are intolerant to them. It is also used in the treatment of bone cancer.
- Teriparatide (Forteo). This medication has the potential to rebuild bone and is most often prescribed for men and postmenopausal women with very low bone density.
- Abaloparatide (Tymlos). This medication can help new bone structure to form and redress the damage related to fractures from osteoporosis. It is the first medication to promote the formation of new bone structure, which is similar to that of pre-existing bone.
Both Teriparatide and Abaloparatide are recommended for a maximum of two years of use, during which time one receives daily injections. Injected medications are most likely to be prescribed to treat:
- People with extremely low bone density
- Children with osteoporosis
- People with multiple fractures
- Osteoporosis caused by steroid medication
Hormone replacement therapy (HRT)
Hormone replacement therapy (HRT) can slow the process of bone remodelling and help increase a woman’s bone mineral density, and can be prescribed for both early and late menopausal women to combat the negative effects of the decrease in estrogen levels that accompany the menopause. It involves regular supplements of estrogens and also progestins in some cases.
HRT is not usually recommended as a long-term or first-line treatment for osteoporosis, because it is associated with severe side effects and health complications:
- Cardiovascular complications (problems relating to the heart including unstable angina or heart attacks, strokes and pulmonary embolism)
- Breast cancer
- Endometrial cancer
- Ovarian cancer
- Breast tenderness
- Vaginal bleeding
Women are usually only prescribed HRT for osteoporosis if all other possible treatments are unsuitable for an individual. When HRT is prescribed for osteoporosis, it should be at the lowest possible dose and for the shortest possible duration.
Preventing falls and fractures
Recent research on osteoporosis and fractures in the elderly suggests that preventing falls is just as important to managing osteoporosis as monitoring and improving one’s bone mineral density.
Doctors are therefore advised to assess people with osteoporosis in order to ascertain the likelihood of falls which could result in fractures. They will use this information to devise preventative measures, suggesting changes to a person’s diet, daily routine and medications as necessary to avert the possibility of future falls.
Factors which one’s doctor may consider in assessing one’s risk of falling and preventative measures include:
- One’s history of falling, including the total number of falls in the previous 12 months
- Location of falls
- Ability to get up independently after falling
- Cognitive function
- Other relevant medical conditions
- Walking and movement
- Muscle strength and function
- Medications which may make dizziness, falling or loss of balance more likely
Changes to one’s home environment and routine which may help prevent falls include:
- Taking regular exercise; even in very elderly people, increased safe physical activity has been shown to reduce the likelihood of falls significantly, in part by improving strength and balance control
- Removing trip hazards like trailing wires
- Having regular hearing and eyesight tests
- Placing non-stick mats on areas which are likely to become slippery, such as the kitchen floor and bathroom
- Eating a healthy diet
Bone fractures resulting from osteoporosis may be more painful than regular fractures due to the splintering of the bone that results from their weakened structure. People with osteoporosis will therefore be prescribed appropriate pain medication in order to manage the pain that results from both specific fractures, and from the generalised pain which often occurs in the spinal area.
Painkilling medications prescribed and/or recommended in the management of osteoporosis may include:
- Nonsteroidal anti-inflammatory drugs (NSAIDS)
- Prescription anti-inflammatory medications
- Nerve blocks
- Opiate painkillers
Ensuring that a person with osteoporosis is able to enact their day-to-day regime as comfortably as possible may require further medical interventions.
These may include:
- Educational measures (to equip an individual to understand their needs and make the best choices to prevent pain)
- Surgical interventions (such as nerve removal)
Prevention of osteoporosis
Osteoporosis is, in part, a hereditary condition, meaning one is particularly susceptible if one’s parents have been affected by osteoporosis. It is nevertheless possible to take measures to help prevent osteoporosis. Adapting one’s diet and exercise regimes, avoiding excessive consumption of alcohol, stopping the use of tobacco products and getting sufficient sunlight are fundamental factors in safeguarding one’s bones against osteoporosis.
People who are sufficiently active and eat appropriately to prevent osteoporosis in childhood and young adulthood, build a stronger bone structure than those who do not, and are significantly less at risk of being affected by osteoporosis in later life.
Both calcium and vitamin D are required for healthy bone development and remodelling. Eating a balanced diet helps provide the body with essential nutrition, which can aid the prevention of a variety of conditions, including osteoporosis.
The body cannot make its own stores of calcium, making it essential that one’s diet includes sufficient sources of calcium to provide one with one’s required daily intake (approximately 700 mg per day for adults).
Sources of calcium include:
- Dairy produce such as milk and cheese
- Soya beans and certain soya products such as soy milk (which are often fortified with calcium)
- Leafy green vegetables such as kale, broccoli and cabbage
- Fish with edible bones such as sardines
- Baked goods made with fortified flour
The body can synthesise vitamin D using its stores of cholesterol when it has access to UVB radiation (sunlight). Some foodstuffs also contain vitamin D, and many products (such as soy milk and orange juice) are fortified with it.
Sources of vitamin D include:
- Oily fish such as trout, salmon, herring, sardines, pilchards, kippers, tuna
- Cod liver oil (this contains large amounts of vitamin D and should not be used in conjunction with other supplements)
- Fortified dairy products
- Fortified soy products
- Raw milk
- Egg yolk
Often, it is not possible – particularly for people living far from the equator – to ensure that one’s intake of vitamin D is sufficient by relying on sunlight and nutritional sources alone.
For this reason, in order to prevent conditions like osteoporosis, it is advisable to take a vitamin D supplement. Adults are recommended to consume a supplement of vitamin D. One should seek advice from a pharmacist or healthcare provider when choosing a supplement to ensure that it and the dosage are appropriate for one’s age and body-type, and that its contents do not overlap with any other supplements or medication one may be using.
Exercise is an essential means of preventing bone loss, which occurs naturally as one ages and can lead to osteoporosis. At least 30 minutes per day of physical exercise are recommended for all adults. Intense daily activity is proven more effective than infrequent, longer exercise sessions.
People with health conditions such as cardiovascular problems should consult their doctor before devising an exercise regime, in order to make sure that the physical activities they choose are appropriate for their capabilities.
Activities which are particularly helpful in the prevention of osteoporosis include:
- Weight-bearing exercise. The best activities for building bone strength are those which compel one to work against gravity, such as weight training, hiking and jogging.
- Regular exercise. Activities like walking fast and cycling constitute moderate-intensity exercise and are easy to incorporate into one’s weekly routine.
- Muscle-strengthening exercise. Activities which build one’s stamina and strengthen one’s muscles such as yoga, skipping and tai-chi can help increase one’s poise and prevent falls in later life.
- Stationary exercise. Many hip, leg and spine exercises which are helpful in strengthening the areas of the body most prone to fractures from osteoporosis can be carried out at home with the use of a straight-backed chair, and are easily incorporated into one’s routine.
Q: How does one’s milk intake in childhood influence one’s risk of developing osteoporosis later on?
A: Milk is a source of calcium, which is essential for the development and growth of healthy bones. The stronger one’s bones develop during their formative years (childhood and adolescence), the more likely they are to age slowly and stably, reducing one’s chances of developing osteoporosis. Daily milk intake in childhood and adolescence has been found to increase bone mass and density in adulthood more effectively than taking calcium supplements for the same purpose, once the skeleton is fully grown. Milk consumption in childhood is therefore advised in order to prevent rapid bone loss and reduce the risk of osteoporotic fracture in adulthood.
Q: What is the difference between osteoporosis and osteopenia?
A: Both osteoporosis and osteopenia are diseases with the primary characteristic of a decrease in bone density and the conditions are caused by the same factors.
Osteopenia involves a lesser degree of damage to the bones than osteoporosis. The distinction between whether a person is affected by osteoporosis or osteopenia is most accurately determined by their bone density score. A score of less than -1 and greater than -2.5 indicates that a person is affected by osteopenia rather than osteoporosis. Osteopenia is a less severe condition involving low bone density which can progress to osteoporosis if left untreated. It is therefore important to seek medical attention if one is at risk of osteoporosis, even if one has not experienced a fracture, in order to identify and begin to treat possible cases of osteopenia. Treatment for both conditions should be focussed on treating the underlying secondary cause(s) where possible.
Q: Is osteoarthritis related to osteoporosis?
A: Osteoarthritis and osteoporosis both affect the bones, but osteoarthritis is a condition which specifically affects the joints, rather than the bones as a whole. In osteoarthritis, the cartilage at the ends of the bones, which connect at one’s joints, wear away, causing the swelling characteristic of arthritis. This causes one’s bones to thicken and harden at the ends, developing new structures called spurs around one’s joints which force the bones out of their normal position.
The primary risk factors of osteoarthritis are being over 40, being female, being overweight and being genetically predisposed to conditions which affect one’s joints. Both osteoporosis and osteoarthritis can cause back pain and height loss. If you think you may be affected by either of these conditions, get a free symptom assessment with the Ada app.
“What people with anorexia nervosa need to know about osteoporosis.” National Institute of Osteoporosis and Related Bone Diseases. April 2016. Accessed: 23 November 2017. ↩ ↩
“Osteoporosis prevention, screening, and treatment: a review.” Journal of Women’s Health. 1 July 2014. Accessed: 23 November 2017. ↩
“Bone microdamage and skeletal fragility in osteoporotic and stress fractures.” Journal of Bone and Mineral Research. 1 January 1997. Accessed: 23 November 2017. ↩
“Age-related hyperkyphosis: its causes, consequences, and management.” Journal of Orthopedic Sports Physical Therapy. June 2010. Accessed: 23 November 2017. ↩
“Which fractures are most attributable to osteoporosis?” Journal of Clinical Epidemiology. January 2011. Accessed: 23 November 2017. ↩
“[Facts and statistics](https://www.iofbonehealth.org/facts-statistics#category-23].” International Osteoporosis Foundation. 2017. Accessed: 23 November 2017. ↩
“Male hypogonadism and osteoporosis: the effects, clinical consequences, and treatment of testosterone deficiency in bone health.” International Journal of Endocrinology. 16 March 2017. Accessed: 23 November 2017. ↩
“Physical inactivity: associated diseases and disorders.” Annals of Clinical Laboratory and Science. 2012. Accessed: 23 November 2017. ↩
“Osteoporosis and parathyroid disease (hyperparathyroidism).” Parathyroid.com. 14 April 2016. Accessed: 23 November 2017. ↩
“Ethanol reduces bone formation and may cause osteoporosis.” American Journal of Medicine. March 1989. Accessed: 23 November 2017. ↩
“Fracture healing in osteoporotic fractures: is it really different? A basic science perspective..” Injury. March 2007. Accessed: 23 November 2017. ↩
”What You Should Know about Tymlos (Abaloparatide) for Osteoporosis.” National Women’s Health Network. 20 May 2017. Accessed: 23 November 2017. ↩
“Shifting the focus in fracture prevention from osteoporosis to falls.” British Medical Journal. 19 January 2008. Accessed: 23 November 2017. ↩ ↩
“Management of chronic pain in osteoporosis: challenges and solutions.” Journal of Pain Research. 01 April 2016. Accessed: 23 November 2017. ↩
“Milk intake during childhood and adolescence, adult bone density, and osteoporotic fractures in US women.” The American Journal of Clinical Nutrition. 23 July 2002. Accessed: 23 November 2017. ↩