Inflammatory bowel diseases (IBD) is a term that describes two conditions, Crohn’s diseases (CD) and ulcerative colitis (UC), which are characterized by the chronic inflammation of gastrointestinal (GI) tract. Traditionally, IBD was regarded as a disease of Westernized nations, but it is now growing at an alarming rate in Asia, and Hong Kong ranks 3rd among Asian countries in terms of high incidence rate of IBD. To date, there are 5,000 IBD patients in Hong Kong, with approximately 26 new cases for every 1 million people.1 On the other hand, IBD seems to have higher association with increased fracture risk, and there is evidently an elevation of risk of osteoporosis in patients with IBD. Obviously, IBD is emerging as a public health challenge worldwide, coupled with the increased risk related to osteoporosis and fractures. Thus, effective preventive health measures for IBD are essential to avert morbidity and improve the quality of life (QOL).2
Osteoporosis is a disease of bones that leads to an increased risk of fracture. Clinical symptoms associated with osteoporosis are a reduction of bone mass density, followed by significant bone microarchitecture deterioration. Generally, patients with a genetic predisposition to osteoporosis are typically thin and postmenopausal women. Besides, factors such as smoking status and alcohol consumption also influence the probability of having osteoporosis. However, the risk factors for those IBD patients affected by osteoporosis differ from the general pattern.2
Patients with pre-existing IBD have a significantly higher risk of developing osteoporosis and increased fracture risk according to the findings from a population-based cohort study population-based University of Manitoba IBD Database. Results derived from 6,027 patients with IBD (mean age, 36, and 42 years for CD and UC, respectively) showed a 40% higher occurrence rate of fracture among people with IBD. Also, the data revealed that patients with IBD had a significantly highest increased incidence rate ratio (IRR) of 1.74 for fractures at the spine, followed by hip (IRR=1.59), wrist/forearm (IRR=1.33) and rib (IRR=1.25).2
Dr. Millie Long, MD, a gastroenterologist from the Department of Medicine at the University of North Carolina in Chapel Hill, further explained at the Gastroenterology Updates IBD Liver Disease Conference 2020, “In the population with IBD, the risk for osteoporosis is similar in women and men, age plays a large role, and corticosteroid use seems to be a driving factor in the development of the disease,” stated Dr. Long. Furthermore, a previous study revealed that fractures in patients with IBD were 40% greater than the general population. Also, the risk of fracture increased with age for patients with IBD.3
Chronic gut inflammation in IBD induces osteoporosis onset through the activation of T lymphocytes resulting in enhanced release of inflammatory cytokines, such as TNFα. They are responsible for causing a bone loss through the modulation of the OPG/RANKL/RANK pathways.
As such, one of the factors contributing to the increased risk of fractures in IBD patients is bone mineral density (BMD). Results from a cross-sectional study showed that 18% – 42% of IBD patients had osteoporosis (T-score<-2.5).4 The meta-analysis of 16 studies of BMD, in which IBD was compared with controls, found that the mean Z-scores for BMD at all sites were lower in patients with IBD (mean difference ranging from -0.5 to -1). Moreover, low bone mass was more common in patients with CD than UC.4
Additionally, the severity of gut inflammation, intestinal malabsorption, together with calcium and vitamin D deficiency, are also linked to the loss of BMD. And the main factor affecting the bone metabolism directly seems to be corticosteroid treatment. From a nationwide follow-up study of 16,416 patients in Denmark, it was suggested that the number of corticosteroids used, and the severity of inflammatory process are part of the reasons for the increased fracture risk.4
In summary, Dr. Long highlighted the burden of IBD by commenting, “Fractures to the hip and spine are linked to significant morbidity, including hospitalization, major surgery and even death. But they are one of the preventable downstream effects of IBD, and patients need to understand that there’s something they can do about their elevated risk.”2 One of the fundamental approaches for risk prevention is to educate patients about the critical advantages of not smoking and performing a weight-bearing exercise.
IBD patients should also undergo dual-energy x-ray absorptiometry (DXA) for the bone density calculation. With such data on hand, a better establishment for the need of calcium and vitamin D supplementation can be facilitated. Vitamin D has long been recognized as important and required nutrients for bone health and maintenance, in order to lower the relevant risks of osteoporosis and fractures for her IBD patients, Dr. Long has decided to carry out vitamin D test screening on them annually.
Given that changes in bone metabolism are frequently associated with the evolution of IBD, effective preventive measures and educational interventions are of utmost importance to improve the rates of morbidity and mortality, and the patients’ QOL.