Bone Health and Osteoporosis Notes

Week 1: Bone Health and Osteoporosis

Learning Outcomes

  • structure of bone.

  • Identify populations at-risk of developing osteoporosis.

  • Provide a detailed explanation of the different nutritional and physical activity requirements for healthy living in humans, according to life stage, sex and health status, in order to elicit improvement in osteoporosis risk.

  • Provide a detailed evidence-based description of the influence of genetic and environmental factors on the effectiveness of physical activity and nutritional interventions for those at risk of osteoporosis.

  • Generate interventions to reduce risk of osteoporosis in the general population and in sport.

What is Osteoporosis?

  • Definition: "A disease characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk" (WHO 1993).

    • Osteo = bone

    • Porosis = porous

Osteoporosis

  • Condition: Weakened bones that are more prone to fractures.

  • Silent Disease: Often no symptoms until a fracture occurs.

  • Affected Populations: More common in post-menopausal females, but can also affect men and children.

  • Tracks disease patterns and trends.

  • Identifies risk factors for diseases.

  • Guides public health policies and interventions.

  • Prevents disease through early detection and prevention strategies.

  • Evaluates effectiveness of health interventions and treatments.

  • Improves resource allocation for public health efforts.

  • Advances global health by addressing worldwide health challenges. Hip, spine, and wrist.

  • Projected Increase: By 2041, hip fractures in Ireland are projected to increase by 150%.

Osteopenia

  • Definition: Early stage of Osteoporosis.

  • Risk Factor: Places a person at risk of developing Osteoporosis.

  • Diagnosis: A warning to start taking care of bones, prevent further bone loss, and implement a bone health plan.

  • Risk Factors: Same as for Osteoporosis.

Diagnosis of Osteoporosis

  • DEXA Scan: Dual Energy X-Ray Absorptiometry measures bone mineral density (BMD), indicating bone quality and fracture risk.

  • Procedure: Simple, painless, and uses very low doses of radiation.

  • Compares BMD to that of a healthy young adult.

  • Reported as T-scores.

T-Scores

  • Normal/Healthy: +1 to -1

  • Mild Osteopenia: T-score = -1 to -1.49

  • Moderate Osteopenia: T-score = -1.5 to -1.9

  • Marked Osteopenia: T-score = -2 to -2.49

  • Osteoporosis: T-score = Greater than -2.5

  • Severe Osteoporosis: T-score = -3.0 and higher (-3.1, -4.5, -5.3)

Bone

  • Living Tissue: The body continually removes and replaces bone.

  • Age-Related Changes: As we age, bone loss is faster than bone formation.

  • Osteoporosis Development: Occurs when new bone formation does not keep up with the loss of old bone.

Bone Remodeling

  • Constant Renewal through remodeling.

  • Cells Involved: Osteoclasts (bone-resorbing cells) and osteoblasts (bone-forming cells).

  • Peak Bone Mass: age 30.

  • Risk Increase: After age 30, bone resorption starts to outpace bone formation, increasing osteoporosis risk.

Role of Bone

  • Support for the Body: Posture, normal joint movement, muscle activity, and functional load bearing.

  • Protection of Organs: Such as the brain and lungs.

  • Reservoir: Of calcium and phosphate.

  • Buffer: Maintains normal acid–base balance.

  • System Maintenance: Normal haemopoietic and immune system through its relationship with bone marrow.

Building Strong Bones

  • Early Life Importance: Building strong bones early in life can reduce vulnerability to osteoporosis later.

  • Peak BMD Increase: A 10% increase in peak BMD may delay osteoporosis development by 13 years.

  • Adolescence: Approx half of bone mass is accumulated during adolescence.

  • Factors Affecting Bone Mass: Genetics, diet, and physical activity.

  • Other Factors: Gender and ethnicity.

Risk Factors – Non-Modifiable

  • Gender: Women are more likely to develop osteoporosis.

  • Age: Risk increases with age.

  • Ethnic Background: Greater risk if Caucasian or Asian.

  • Family History: Higher risk if there is a family history of osteoporosis, especially a fractured hip in a parent.

  • Body Frame: Small-boned body frame.

Risk Factors – Modifiable

  • Physical Activity: Higher risk if sedentary.

  • Smoking: Contributes to weaker bones.

  • Excess Alcohol: Regularly consuming more than two alcoholic drinks a day increases risk.

  • Diet: Insufficient calcium and vitamin D intake increases risk.

Additional Risk Factors

  • Eating Disorders/Over Exercising: Can cause significant bone loss and affect overall health and fertility.

  • Vegan Diet: May increase risk of bone loss; vegans should monitor bone health.

Medical Conditions and Medications

  • Long-term steroid use.

  • Chemotherapy and Radiation: Cause significant bone loss.

  • Overactive thyroid or parathyroid gland.

  • Early menopause (before 45).

  • Loss of periods not due to pregnancy.

  • Conditions affecting nutrient absorption, such as Coeliac or Crohn’s disease.

  • Medications for breast cancer, prostate cancer, and epilepsy; Protein pump medication for acid reflux.

Osteoporosis Risk Factors - SHATTERED

  • S – Steroids (Sedentary)

  • H – Hyperthyroidism/hyperparathyroidism

  • A – Alcohol and tobacco

  • T – Thin (BMI <22kg/m2)

  • T – Testosterone (low e.g. prostate Ca)

  • E – Oestrogen (low/reduction at menopause)

  • R – Renal/liver failure

  • E – Errosive bone disease/Inflammatory bone e.g. rheumatoid arthritis

  • D – Dietary Calcium (low intake/malabsorption)

The Silent Disease

  • Vertebral fractures: Occur during daily activities without a fall.

  • Symptoms: Back pain, limitation of spine mobility, height loss, and disability.

  • Asymptomatic Fractures: 66% of vertebral fractures have no symptoms.

  • Hunching Back: Vertebral fracture is a cause of hunching in the elderly.

The Size of the Problem

  • Development: Develops throughout life, from in utero until old age.

  • Prevalence in Ireland: Approximately 300,000 people older than 50 years have osteoporosis (25% of this population).

  • Worldwide Hip Fractures: Estimated at 6 million hip fractures per year.

  • Cost of Long-Term Disability: In 2010, cost in the EU was €10.7 billion.

  • First Described: Mid 20th Century and has been rising ever since.

Ethnicity and Race

  • Important Factors: Influence the prevalence of osteoporosis.

  • Highest Fracture Rates: Found among white women.

  • Rates in Black Women: About 50% lower than white women in the United States.

  • Rates in Hispanic and Asian Women: Generally about 25% lower than rates in white women.

Ethnicity and Bone Density

  • Black African Descent: People of black African descent have higher bone density than Europeans.

  • Asians and Black People: Have a lower fracture risk at any given bone density.

  • Explanation: Unclear at present.

Geographic Variation in Hip Fracture Incidence: Europe

  • Correlates:

    • Latitude

    • Sunlight

    • Activity

    • BMI

    • Height

    • Fall risk

    • Not BMD

FRAX Score

  • 10-year fracture risk.

  • Calculation Tool for fracture risk assessment.

Role of Bone (Reiterated)

  • Support for the Body: Posture, normal joint movement, muscle activity, and functional load bearing.

  • Protection of Organs: Such as the brain and lungs.

  • Reservoir: Of calcium and phosphate.

  • Buffer: Maintains normal acid–base balance.

  • System Maintenance: Normal haemopoietic and immune system through its relationship with bone marrow.

Maximum Strength, Minimum Weight

  • Diaphysis: Long central shaft.

  • Epiphysis: Large rounded ends of long bones.

  • Metaphysis: Area between the diaphysis and epiphysis at both ends of the bone.

  • Epiphyseal Plates: Plates of cartilage, also known as growth plates which allow the long bones to grow in length during childhood. These plates stop producing cartilage cells between 18 and 25 years of age and are gradually replaced by bone.

Bone Structure – Cross Sectional

  • Periosteum: Dense but thin layer that contains blood vessels.

  • Compact/Cortical Bone: Hard dense bone matrix (85% of bone weight).

  • Spongey/Trabecular Bone: Lightweight porous bone architecture (15% of bone weight).

  • Bone Marrow: Fatty tissue/blood cell producing tissue housed in the medullar shaft of the bone.

Types of Bones

  • Classification: Classified by shape (long, short, flat, or irregular).

  • Number of Bones: 206 bones in the adult human skeleton.

  • Axial Bones: 80 bones, including the skull, hyoid, auditory ossicles, vertebral column, ribs, and sternum.

  • Appendicular Bones: 126 bones, including arms, shoulders, wrists, hands, legs, hips, ankles, and feet.

Types of Bone Cells

  • Osteoblast: Forms new bone tissue, remodels bones while aging, and heals damaged bones.

  • Osteoclast: Dissolves, reabsorbs, and removes unwanted bone tissue.

  • Osteocyte: Maintains bone as living tissue.

  • Hematopoietic: Found in bone marrow, makes red blood cells, white blood cells, and platelets.

Bone Matrix

  • Definition: Intercellular substance of the bone that forms most of the mass of the bone.

  • Organic Component – Collagen Fibers: Provide flexibility and tensile strength (30% of bone's weight).

  • Inorganic Component – Mineralized Components: Mainly calcium phosphate in the form of hydroxyapatite crystals (60% of bone weight).

Osteoblasts & Osteocytes

  • Osteoblasts build up bone.

  • They make the bone matrix and are responsible for mineralisation (maturation) of the bone.

  • Osteocytes are osteoblasts that are on the inside of the immature bone matrix (osteoid), which will eventually become mature calcified bone.

  • Osteocytes respond to changes in force on the bone, e.g. resistance exercise controlling break down and building of bone.

Osteoclasts – Bone Resorbing Cells

  • Osteoclasts collapse bone.

  • Osteoclasts allow the release and resorption mineralised tissue (Ca/P mature bone)

  • Resorption = “To reabsorb; to absorb what has been excreted

  • In this instance, the blood is resorbing Calcium and Phosphate into the circulation.

Osteoclasts

  • Location: Sit on the surface of the bone at active bone resorption sites.

  • Stimulation: Parathyroid hormone, vitamin D, and inflammatory cytokines stimulate osteoclast activity.

  • Reduction: Calcitonin reduces osteoclast activity.

Calcium

  • Roles: Blood clotting, muscle contraction, regulating heart rhythms and nerve functions.

  • Maintenance: Body keeps a steady amount of calcium in the blood and tissues.

  • Low Calcium Levels: Parathyroid hormone (PTH) signals bones to release calcium into the bloodstream; also activates vitamin D to improve calcium absorption in the intestines. PTH signals the kidneys to release less calcium in the urine.

  • High Calcium Levels: Calcitonin lowers calcium levels by stopping the release of calcium from bones and signaling the kidneys to rid more of it in the urine.

Upregulation Response to Low Circulating Calcium

  • Low ionized Ca circulating in the blood

  • Increased synthesis & release of PTH from parathyroid gland.

  • Increases release of active Vit D

  • Increased Calbindin synthesis

  • Increased transcellular transport of dietary Ca to the plasma

Downregulation Response to High Circulating Calcium

  • High levels of Ca circulating in the blood

  • Thyroid gland releases Calcitonin hormone

  • Inhibits breakdown of bone thus stopping release of extra Ca from bone into blood stream.

  • Decreases calcium resorption in the kidneys

  • Lower levels of circulating CA

Bone Remodeling Cycle

  • Resorption: Osteoclasts remove a portion of the bone.

  • Reversal

  • Formation: Osteoblasts lay down collagen and mineral deposits.

Modifiable and Non-Modifiable Factors

  • List the modifiable and non-modifiable factors affecting bone health.

Genetic vs. Environmental Factors

  • Paediatric Disease, Geriatric Consequences

  • Non-modifiable risk factors = genetics (60-80%)

  • Modifiable risk factors = environmental (20-40%)

Age and Bone Mineral Accretion

  • Peak bone mineral accretion: 12.5 ± 0.90 years in girls and 14.1 ± 0.95 years in boys.

  • 40% of BMD is acquired during peak.

  • 95% of adult bone mass: Achieved 4 years following the peak.

  • A 10% increase in PBM in children: Reduces the osteoporotic fracture risk in adulthood by 50% and delays the onset of osteoporosis by 13 years.

Bone Mass Throughout the Life Cycle

  • Age-related changes in bone mass, peak bone mass, and the effects of menopause are highlighted graphically.

Key Life Stages

  • Foetal development

  • Children

  • Puberty and adolescence

  • Adults

  • Pregnancy and lactation

  • Elderly

Sex and Oestrogen

  • Oestrogen inhibits bone resorption.

  • A drop in oestrogen causes approximately 20% loss of BMD in the seven years following menopause.

  • Menopause – Age 50

  • Early Menopause – Before 40 years, causes increased risk of any fracture.

  • Treatment (HRT or Ca/Vit D) Did not impact increased fracture risk, suggesting early menopause is an independent risk factor.

Pregnancy & Lactation

  • Calcium Absorption: Pregnant women absorb calcium better.

  • Estrogen Production: Women produce more estrogen, which protects bones.

  • Bone Mass Restoration: Bone mass lost during pregnancy is typically restored within several months after delivery or stopping breastfeeding.

Pregnancy & Lactation Considerations

  • Multiparity: Not a risk factor in osteoporosis.

  • Early pregnancy: Increases risk of osteoporosis.

  • Breastfeeding >1yr: Potentially increases risk of osteoporosis.

  • Late period (>15yrs), or early menopause (<45yrs)

Family History

  • Meta-analysis showed an increased risk of fracture in both males and females with a parental history of fracture.

  • Risk was independent of BMD.

Fracture Risk

  • Any fracture: 17%

  • Osteoporotic fracture: 18%

  • Hip fracture: 49%

Modifiable Risk Factors

  • Low BMI

  • Smoking

  • Alcohol

  • Weight-bearing exercise

  • Dietary calcium

  • Vitamin D

  • Dietary protein

  • Breastfeeding >1yr?

Low BMI

  • BMI <20 kg/m² is associated with greater bone loss and increased risk of fracture.

  • People with a BMI of 20kg/m2 have a two-fold increased risk of fracture compared to people with a BMI of 25 kg/m²

Smoking

  • Smoking is associated with low BMD.

  • Current smoking = 13% increase in ‘any fracture’ risk compared to non-smokers.

  • Current smoking = 60% increased hip fracture risk compared to non-smokers.

  • 23% of hip fracture risk was due to low BMD of smokers, the rest was independent of BMD.

  • The effect of smoking appears to wane slowly after a person stops smoking

Possible Smoking Causes

  • Dependent on BMD

    • Smoking women also have earlier menopause.

    • Smoking may enhance estrogen catabolism.

    • Smokers are thinner, and therefore have lower BMD.

  • Independent Risk

    • Possibly from lower levels of physical activity or to co-existing morbidity.

    • Smoking-induced changes in the microarchitecture of cancellous bone.

Alcohol

  • Non-linear relationship between alcohol intake and fracture risk.

  • Up to 2 units per day results in no increased risk.

  • > 2 units/day:

    • Any fracture: 23%

    • Osteoporotic fracture: 38%

    • Hip fracture: 68%

Alcohol and Bone Health

  • Excessive alcohol intake can increase the risk of developing osteoporosis.

  • Inhibits Bone Formation

  • Impaired Calcium Absorption

  • Disrupts Hormonal Balance

  • Increases Risk of Falls and Fractures

Exercise

  • Weight-bearing exercise and resistance exercise are particularly important for improving bone density and helping to prevent osteoporosis.

  • Weight bearing exercises involve moving the body’s weight against gravity with the legs and feet supporting the body’s weight.

Exercise Types

  • High-impact:

    • Basketball

    • Volleyball

    • Track events

    • Star jumps

    • Tuck jumps

    • High-level jumps

  • Moderate-impact

    • Jogging

    • Running

    • Team sports

    • Racket sports

    • Skipping and hopping

    • Low level jumps

  • Low Impact

    • Walking

    • Brisk walking

    • Marching

    • Stamping

    • Stair climbing

Weight Bearing Exercise

  • Regular exercise = developing stronger muscles & bones = improve balance & reduced bone loss = experience fewer falls and fractures.

  • Upon exercise, bone tissue deforms, and the mechanosensors located throughout the cells, such as stretch-activated ion channels and integrins, change their original conformation.

  • Conformational changes trigger a signalling cascade to provide an appropriate biochemical response which is osteogenesis and bone accretion at the site of deformation.

BMD and Sport

  • Athletes high impact exercise exhibit higher densities of cortical and trabecular bone than matched controls

  • greater bone mass observed in the more active limb.

  • 6-months of spaceflight results in a 10% loss in the BMD

Calcium Supplementation

  • Supplementation of adolescent girls for 18 months resulted in a gain of total body bone mineral density of 9.6% compared with a gain of 8.3% in placebo-treated girls.

  • At 2 years, the gains were 12.1% and 10.1%, respectively.

  • Skeletal gains disappeared when calcium was stopped.

  • Other studies reporting the effects of calcium supplementation in children are equivocal and have generally shown no effect on growth.

Calcium and Vitamin D Recommendations

  • Intakes of 1,200mg/day Ca, 800-100 IU vitamin D and 1g/kg body weight protein can be recommended in the general management of patients with osteoporosis.

Dietary Sources of Calcium

  • Dairy products (milk, cheese and yoghurt), especially the fortified milks, as they have calcium and vitamin D3.

  • Bread, nuts, oily fish, sesame seeds, dried fruit, and tofu also contain calcium, as well as some dark green vegetables.

Know Your Risk Factors

  • Risk factors for osteoporosis include:

    • Broken a bone after age 50

    • Smoking

    • BMI < 19kg/m²

    • Parental osteoporosis

    • Early menopause (before age 45)

    • Loss of height > 3cm

    • Rheumatoid arthritis

    • Glucocorticoid or cancer treatment

    • Celiac, Crohn's disease, diabetes

Health Promotion

  • The Irish Osteoporosis Society (IOS) plays a key role - increase their calcium intake and engage in weight-bearing physical activity.

Key Questions

Answers to Key Questions

  • What tools do doctors use diagnose osteoporosis? DEXA

  • What is the definition of osteoporosis? T-Score <-2.5

  • What is the definition of osteopenia? T-Score -1 to -2.5

  • What percentage of our calcium is stored in bones and teeth? 99%

  • What percentage of our calcium is stored in the blood? 1%

  • What two minerals is the bone complex made from? Ca, P

  • What hormone has a key role in calcium homeostasis? Parathyroid Hormone