Osteoporosis is a metabolic disease of the skeleton characterized by a decrease in bone mass, impaired microarchitectonics of bone tissue and, as a result, fractures with minimal damaging effects (falling from one's own height, sudden movements, lifting small weight and even sneezing or coughing). Such fractures are considered pathological, as they occur due to significant impairment of bone durability. Osteoporosis ranks fourth as a cause of disability and mortality after such pathologies as cardiovascular diseases, cancer, diabetes mellitus.
Epidemiology of osteoporosis
The issue of osteoporosis has acquired medical and social significance only since the second half of the 20th century due to a significant increase in life expectancy and, accordingly, the number of elderly people in the population of many European and North American countries, and improved diagnostic techniques associated with the development of biochemical and radiological examination methods.
The development and progression of the bone mineral density loss and osteoporosis propagation are facilitated by a decrease in motor activity (automation of operations and in household activities, prevalence of vehicles), malnutrition, resulting in an excess body weight (the development of metabolic syndrome, diabetes mellitus), the presence of unhealthy habits (smoking, alcohol), the extensive use of corticosteroids and a number of other medications, low vitamin D levels, and a number of other factors.
The main risk factors are female gender and old age. Osteoporosis affects from one third to half of postmenopausal women and almost half of the population of both sexes after the age of 75. In the future, the issue of osteoporosis will become even more serious, as society ages in general. According to the World Health Organization, the frequency of fractures with underlying osteoporosis will triple in 2050.
In Russia, epidemiological studies of osteoporosis prevalence have been conducted recently, but a preliminary conclusion about its substantial prevalence may be drawn. Thus, signs of osteoporosis were detected in 37.4% of Moscow residents over the age of 50 during spine radiography, and osteoporotic fractures of vertebral bodies were detected in 11.8%. The risk group also includes people who regularly use steroid drugs, as well as those with diseases of the gastrointestinal tract.
Etiology and pathogenesis
The bone is an indicator of all changes and features of the body, genetic code, age, gender, lifestyle, physical activity, concomitant diseases and conducted therapy.
Bone tissue starts to develop in the early years of life, reaches its maximum density by the age of 25, remains almost unchanged until the age of 35-40, and then begins to gradually decrease. In women, the rate of bone mineral density loss is higher than in men, which is associated with estrogen deficiency during peri- and postmenopause. However, it is constantly updated: resorption of old bone tissue occurs with the formation of a new one. 2-4% of bone tissue is rebuilt annually (half of the skeleton is renewed in 10-20 years). Normally, these processes are balanced, but with osteoporosis development, resorbed osseous lacunae are filled in 1-2 years instead of 5-8 weeks, which leads to a decrease in bone tissue volume. This is facilitated by a number of reasons (genetic, hormonal, alimentary, mechanical). As a result, the bone substance formed in the early years of life is gradually "consumed" in the aging process. The physiological process of bone loss from 0.5 to 1% annually begins to play an important role at the age over 50. The average annual decrease in bone mass by about 3-5% may last about 10-20 years in postmenopausal women, as well as in women and men in old age. The total loss during lifetime is about 30-40% of the peak bone mass in women and about 20-30% in men.
It is established that about 16% of people possess a genotype that causes the risk of osteoporosis. By the age of 65, i.e., on average 11 years earlier than normal, people with this genotype reach the threshold, beyond which the risk of pathological fractures occurs. Age, pharmacologic treatment, diseases, genetic predisposition and a number of other factors form a multi-faceted model of osteoporosis.
Classification
It is necessary to differentiate between osteopenia and osteoporosis.
Osteopenia refers to changes in bone mineral density preceding osteoporosis, leading to its decrease without the consideration of causes and nature of its structural changes. In osteopenia, the decrease in bone mineral density is still insignificant, which, as a rule, does not manifest clinically or manifests slightly. As osteopenia progresses, osteoporosis develops with postural disorders, spinal deformities, constant back pain, and a high risk of pathological fractures. Thus, with the osteoporosis development, quantitative changes turn into qualitative ones, which is clinically clearly manifested.
The development of diagnostic methods and the emergence of the ability to measure bone mass in different skeleton parts (densitometry, CT) made it possible to distinguish the concepts of "osteopenia" and "osteoporosis" more clearly. The main indicator in this case is the standard deviation from the norm (i.e., peak bone mineral density at 25 years). A decrease in bone density by 1-2.5 standard deviations from normal values of the peak bone mass is regarded as osteopenia, more than 2.5 standard deviations - as osteoporosis. The term "osteopenia" (osteopenic syndrome) is also used in cases when differential diagnosis for bone mass loss has not yet been carried out with other types of metabolic osteopathies.
Primary and secondary osteoporosis are distinguished.
Primary osteoporosis is most frequently observed (up to 85% of cases). It is divided into:
- postmenopausal (type 1 - due to estrogen deficiency in women aged 55-70);
- senile (type 2 - vitamin D deficiency due to various factors);
- juvenile (rare), develops at the age of 12-14 years and is mainly genetically predetermined;
- idiopathic (develops in the period from 25 to 55 years).
Secondary osteoporosis may be caused by: