RISK FRACTURES ASSOCIATED WITH OSTEOPOROSIS

The most common risk factors for osteoporosis in women include genetic predisposition, ethnicity, old age, low body mass index, estrogen deficiency and use of steroid medications. Other or less common risk factors include excessive alcohol use, smoking, low calcium intake, reduced physical activity, previous fracture, poor balance, use of certain medications, and history of certain diseases. Over a lifetime, women lose about 50% of bone density at the spine and 30% at the hip.

• Genetic Predisposition 
  Bone mass is thought to be largely determined by genetics. Genetic factors account for approximately 60% of the variance in bone mass. Genetics also play a role in body mass index. A history of maternal hip fracture and greater height has also been associated with increased risk of fractures.
  
• Ethnicity 
  Caucasian and Asian ethnicity increases the risk of osteoporosis over African Americans and Hispanics. Hispanics tend to have bone density similar to Caucasians, but they have a lower fracture incidence.
  
• Old Age 
  The rate of bone loss increases with age. Studies suggest there is a fairly linear decrease in cortical bone mass with increasing age.
  
• Low Body Mass Index (BMI) 
  Women with a thin body frame are at greater risk of osteoporosis that those with a high BMI. It has been suggested that a high BMI may be protective against osteoporosis.
  
• Estrogen Deficiency 
  Estrogen deficiency is a dominant pathogenic factor in bone loss. In young women, anorexia nervosa, menstrual irregularities or amenorrhea are associated with decreased bone density. Estrogen deficiencies in these situations leads to an imbalance in bone remodeling, enhancing bone resorption. Estrogen deficiency also reduces intestinal calcium absorption, which decreases bone density.
  
• Rapid bone loss is associated with menopause. Menopause results in a 3% reduction in bone mass per year for the first five years. The rate of bone loss after the first five years following menopause ranges from 1% to 2% per year. This results in dramatic changes in bone architecture, which increases the risk of fracture. The accelerated loss of bone mass with menopause causes increased osteoclastic activity, or increased bone resorption. In menopause, a decreased level of estrogen diminishes the effects of growth factors and calcitonin, and decreases vitamin D metabolism and calcium absorption. Vitamin D is required for intestinal calcium absorption. With advancing age, the kidney produces less active vitamin D and there is less efficiency in intestinal absorption of vitamin D and calcium.
  
• Steroid Medications 
  The use of steroids results in increased renal excretion of calcium and decreased intestinal absorption of calcium. Parathyroid hormone levels increase with decreased levels of calcium, resulting in increased bone resorption. Bone loss occurs in patients taking as little as 7.5mg of prednisone a day, with the greatest loss occurring during the first three months of steroid treatment. Postmenopausal women lose bone faster with even less steroid dosages. It has been documented that patients taking 35mg to 50mg of prednisone every two days results in a 17% bone loss per year.
  
• Excessive Alcohol Consumption 
  Excessive use of alcohol has been associated with bone loss, but the exact mechanism by which this occurs is unclear.
  
• Smoking 
  Smoking tobacco has been found to have negative effects on bone also.
  
• Low Calcium Intake 
  The adequate intake of calcium is critical to achieving optimal peak bone mass and modifying the rate of bone loss associated with aging. Most Americans fail to meet the recommended daily allowance for calcium after age 10. Ninety-nine percent of total body calcium is found in bone. Calcium requirements vary throughout an individual's lifetime, with greater needs in childhood and adolescence to build peak bone mass, and in later adult life to prevent excessive loss of bone mass. Calcium insufficiency due to low calcium intake and reduced absorption results in an accelerated rate of age-related bone loss in the elderly population.
  
• Reduced Physical Activity 
  Immobilization and bed rest results in an increase rate of bone loss. A decrease in physical activity can also lead to decreased balance, increasing the risk of falls. Inactivity also leads to an increase in urinary calcium excretion.
  
• Excess Thyroid Hormone 
  An excess of thyroid hormone is usually due to either over-replacement or Grave's disease. Postmenopausal women who are not taking estrogen and have hyperthyroidism have an increased risk of developing osteoporosis.
  
• Rheumatoid Arthritis 
  It has also been found that women with rheumatoid arthritis are twice as likely as other women to have osteoporosis. Significant reductions in bone mass density are found in the femoral neck, total hip area, and in the spine at L2-4 in women with rheumatoid arthritis.

Although most research in osteoporosis has focused on women, several studies have been performed focusing strictly on men. The studies have found that most risk factors for women also apply to men.

• Age Related Changes in Bone Mass 
  Changes in bone mass with aging in men have been found to be similar as the changes in postmenopausal women. Studies have found that age is associated with a linear decrease in cortical bone mass in both men and women, and that bone mineral density decreases in men after 50 years of age. The specific bone remodeling imbalance that is responsible for the age related decline in bone mass in men is unclear.
  
• Clinical Hypogonadism 
  Bone loss results from the appearance of hypogonadism in adults, and a failure to achieve peak bone mass with the onset of hypogonadism before the onset of puberty.
  
• Weight 
  Heavier men have greater bone density and weight loss has been associated with greater rates of bone loss and higher rates of fracture in older men.
  
• Corticosteroid Use 
  Use of corticosteroids has been found to lead to a 2.6 fold increase in the risk for osteoporosis in men.
  
• Tobacco Use 
  A 2.3 fold risk increase in osteoporosis has been found in men using tobacco.
  
• Genetics 
  A major part of the determination of adult bone mass is under genetic control; however, the nature of the relationship is not well established in either sex.