Dem Bones
Never mind making old bones - how can people with HIV stop them thinning and
breaking in the first place? Robert Fieldhouse scans the
evidence
Illustration: Raffaele Teo
Make
no bones about it: long-term HIV infection and some HIV meds can be bad for
our bones. We seem to be at increased risk of ‘thinning bones,’
but there’s lots we can do to keep our bones healthy. It may sound strange,
but as we live longer the more we need to do to take care of our skeletons.
They give our body structure, allow us to move in many ways and, most importantly,
protect our internal organs.
Keeping it together
Each adult has a skeleton made up of 206 bones. Babies are born with about
300 but around 100 normally fuse together throughout child and early adulthood.
If you have ever seen a real skeleton you could be forgiven for thinking all
bones are dead. Although bones displayed in museums are dry, hard or crumbly,
those in our living bodies are very much alive, growing and changing all the
time, just like other parts of our body.
What’s in a bone?
Almost every bone in our bodies is made of the same materials: the outer surface
is periosteum, a thin, dense membrane that contains nerves and blood vessels
that nourish the bone. The next layer is made up of compact bone that is smooth
and very hard. This is the part you see when you look at a skeleton. Within
the compact bone are many layers of cancellous bone which looks a bit like
a sponge. Cancellous bone is not quite as hard as compact bone, but it is
still very strong. In many bones, the cancellous bone protects the innermost
part of the bone: the bone marrow. Bone marrow is like a thick jelly, and
its job is to make red and white blood cells as well as platelets for blood
clotting.
What’s to blame?
Research shows people living with HIV are more likely to experience thinning
bones compared to HIV negative people. It’s still unclear which drugs
are most likely to have a negative effect although some studies have suggested
protease inhibitors are implicated. More studies are needed to identify which
drugs are most likely to cause problems, but it seems long-term HIV itself
is the likely culprit.
Osteopenia
Osteopenia is a term describing any loss of bone mineral density. Various
studies suggest it is relatively common in people living with HIV, affecting
around one in three. Five years ago, researchers at the Royal Free Hospital
in London showed that almost three quarters (71 per cent) of patients in their
study had signs of thinning bones, and the risk appeared to increase among
people on antiretroviral therapy.
Osteoporosis
If bone density decreases to the point where risk of fracture becomes four
or five times higher than normal, one is said to have progressed to osteoporosis.
It is commonly referred to as ‘thinning of the bones’ and typically
occurs in post-menopausal women, where it is caused by a lack of calcium and
protein.
Until recently, osteopenia and osteoporosis were rarely seen in people living
with HIV. Quite why relatively young people with HIV develop osteoporosis
is still unclear, but HIV infection and some HIV treatments may be at the
root of the problem. Osteoporosis has been reported in between three and 21
per cent of HIV positive clinic populations investigated.
Osteonecrosis
Osteonecrosis or avascular necrosis is a painful condition where the blood
supply to the bones is cut resulting in the death of the bone tissue. This
typically affects the hip and knees. Though rare, it has been reported in
people with HIV. Perhaps we are all going to live long enough to need hip
replacements, just as many of our grandparents have. I’d like to think
so.
Latest research
Recent research from France suggests the longer someone has been HIV positive
and the longer they have been on antiretroviral treatments the greater the
risk of developing osteonecrosis. Researchers analysed the clinic records
of over 5,300 people in the French hospital database. People who had had an
Aids-defining illness or a CD4 count below 200 or 50 cells, as well as those
on HIV treatment for the longest time, were at the most increased risk of
developing osteonecrosis. But they were unable to identify which particular
HIV drugs were associated with that increased risk.
How are thinning bones diagnosed?
Reduced bone mass can be diagnosed using a DEXA scan (dual-energy X-ray absorptiometry),
an X-ray that measures the density of different body compartments such as
fat and bone.
Common risk factors for osteoporosis in HIV negative people include having
a family history, having an early menopause, low testosterone levels in men,
prolonged corticosteroid or anticonvulsant use, low calcium intake or poor
absorption of calcium, smoking cigarettes, low body mass and having a sedentary
lifestyle.
Prevalence in women living with HIV
Women living with HIV appear more than twice as likely as HIV negative women
to experience thinning bones, but researchers have failed to show any association
with antiretroviral therapy. Risk factors include having a low body mass index,
a history of low body weight, low body fat percentage and infrequent periods.
Recent research suggests women living with HIV have abnormally low bone mineral
density compared to HIV negative women. Researchers found 41 per cent of HIV
positive women had osteopenia while seven per cent had osteoporosis.
Bone loss was significant even in young, pre-menopausal women with HIV. Women
of low weight or with a history of severe weight loss and low vitamin D levels
were most likely to experience significant bone loss. Researchers are currently
studying the relationship between low testosterone levels and bone loss and
the possibility of giving testosterone replacement therapy to women with HIV.
What
can be done?
• Exercise can improve bone density and bone strength
• A daily calcium intake of at least 1,500mg can help to slow bone loss
- equivalent to two or three servings of dairy produce
• Daily vitamin D intake of between 400 and 1000IU is sensible if you
live in northern Europe, which has low levels of sunlight for more than six
months of the year.
• Anabolic steroids can increase spinal bone density by around two to
three per cent after treatment but have no effect on the rate of fractures.
Severe bone problems
In severe osteoporosis, several drugs have been tested to see if they reduce
the risk of fractures. A modified form of vitamin D called calcitriol reduced
fractures in post-menopausal women. A range of drugs including disodium etidronate,
calcitonin and alendronic acid have all been approved for the treatment of
osteoporosis in post-menopausal women.
However, few studies have looked at whether these treatments are safe and
effective for people living with HIV who have osteoporosis. One compared vitamin
D and calcium supplementation with or without alendronic acid in 31 people
living with with osteopenia. It found spinal bone mineral density improved
by five per cent in the alendronic acid group and by only one per cent in
the supplement-only group after 48 weeks of treatment.
Switching from protease inhibitors to other drug classes has not been shown
to improve bone mineral density 48 weeks after switching, suggesting either
that improvements may take longer, or that protease inhibitors are not the
cause.
Some, but not all, clinical trials offer access to DEXA scans. It’s
worth asking at your treatment centre about what’s on offer and if you
are eligible. If you have had pains in your bones, let your doctor know and
ask what you should do about it.
