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OSTEOPORISIS

Abstract:  Osteoporosis, the disease of declining bone density, produces substantial subtractions of the potential Well-days of healthy life of our population from fractures of the hip, vertebra, and other bones as people age.  Risk of hip fracture moves up ten times as age moves from 70 to 90, and at least  20% of those suffering such fractures will die within a year.  Risk is increased by smoking and excessive alcohol consumption, and can be much higher for small people and especially women of low body weight than for those larger and heavier.  Risk can be reduced most effectively by brisk walking but this must be maintained into oldest age for effective protection.  Adequate dietary and supplement calcium will reduce risk somewhat and use of post-menopausal female hormones can help some women.  All people and especially women should get periodic bone density tests as they move much past age 60, and keep in consultation with their doctors because available medications can help further in reducing risk.

Background:  Osteoporosis is a disease produced by the declining of bone density throughout the body that usually progresses with age. This disease can be invisible to individuals until they suffer some type of a bone fracture that was not caused by an evident and unusually severe injury as from an accident. The key disability caused by osteoporosis usually is a fracture of the hip that occurs as individuals become older. Despite much progress in recent years in the replacement of hips, this event remains as a very serious health problem.  Other problems suffered by those having osteoporosis are fractures of the vertebrae in the spine, the wrist, the ribs, the ankle and the foot.

The only clearly definitive research data found for the effect of sex and age on risk of hip fractures was published by De Laet of the Netherlands (De Laet, BMF 1997; 315:221).  Results of this analysis that probable are indicative of risks for most US white persons are:

                        Percentages of the Population that on Average will suffer a Hip Fracture in one year

Note that these annual risks are about 50% larger for women than for men and increase sharply with age. Risks before age 70 are small.  Cumulative average risks to age 80 are 5.3% and 7.9% for men and women respectively, and risks move up much higher at higher ages.   Research shows that about 6% of all hip fractures result in a soon thereafter hospital death, and that 13-14% of those having these fractures die within the following 6 months.  These fractures that usually happen to older persons can be a traumatic experience that triggers pneumonia and other death causing events. Although hip fractures are usually the most serious consequences of bone disease, they represent only 20% of osteoporosis caused fractures.  Fractures of the vertebra occur to a similar extent, and fractures of the wrist, ribs, ankle or foot occur to 18%, 12%, 9% and 6% of osteoporosis afflicted individuals respectively.  As a quite conservative estimate, Life Ahead assumes that 20% of hip fractures will develop to osteoporosis produced deaths in the same year.

The rate of osteoporosis can be reduced by appropriate exercise, adequate intake of calcium and vitamin D, and for women by use of post-menopausal hormones.  Its rate will be increased by cigarette smoking, and curiously, by underweight.  More on this and some of the key research found on osteoporosis risks follows.

Although bone appears to be rigid and strong, it is a living mechanism of complex chemistry. Its most essential need is to be exercised and used.  Without use bone tends to become weaker and more brittle.  Thus its health appears highly related to the extent it is exercised or stressed.  Heavier and larger people place more stress their bones more than do small people, and thus their bones tend to remain stronger and healthier.  This creates a curious reversal in the usual effect of body weight on health:  For osteoporosis, small people and especially small underweight women have the highest risk; large heavy people have lower risk.  Exercise of any kind, and especially that that stresses bones keeps them more healthy. And bones need a special type of nutrition to keep them in best health and strength.

Osteoporosis and Smoking:  Research studies A1-A4 in the table following show the key research results found on osteoporosis for cigarette smoking.  Although research on smoking is less extensive than for most other major diseases, it seems clear that regular smoking over time increases risk of hip fractures from 1.5 to 2 times. Life Ahead uses the general model for amount and time of smoking that best fits this available information for those still smoking cigarettes.  Basic risks of this and all other diseases are computed for persons that do not now smoke and have not smoked for at least ten years. The higher risks for smokers are computed from this non-smoker base.

Osteoporosis and Body Weight as BMI:  Many studies and reviews cite the fact that small light people have higher risks of osteoporosis caused fractures than do larger and heavier people.  But the key quantitative results on this found are the appended results of studies C1 and C2.  A formula from this research that relates risk of hip fracture to BMI follows the appended table.  This shows risks decreasing from about two fold at a BMI of 18 to values of about 0.95 to 1.1 for women and men of the average BMI of 24-26 used in Life Ahead.  These risks move down further to a factor or 0.64 at 30 BMI and 0.53 at 34 BMI..  Men and women that have a family risk of osteoporosis or other high risks should be aware that although weight reduction can improve health overall, it can worsen the risk of a serious hip or other fracture. Thus individuals at risk should obtain bone density tests as they move much past age 60-65.

Although overweight reduces risk of osteoporosis, a closely related disease is that of arthritis. Arthritis is a much more prevalent problem than is life threatening osteoporosis, and the effect of overweight BMI on arthritis is highly negative.  A combination of these effects of BMI on risk of death for both osteoporosis and arthritis shows a quite negative or harmful effect of weight on the sum of the two diseases.  Life Ahead reflects the net effect of BMI on the sum total risks of these two life diminishing diseases.

Osteoporosis, Hip Fracture and Exercise:  The effect of the exercise of older adults on bone fractures has been extensively researched.  Appended studies B1 through B7 include those found that included useful quantification of exercise and risk of fractures.  The large study of nurses B6 provides the best published relationships of risk of hip fracture with amounts and pace of walking. Walking will constitute by far the major useful exercise of the older adults that are at high risk for osteoporosis.  The results show that pace of walking - and not just amounts of it - is the key that protects.  This is consistent with what would be forecast from the exercise that produces cardiofitness. Although it would not be expected that fitness of the cardiovascular system would be a key here, both amounts of exercise and the stress that this exercise exerts on bone appear to be the key factors that reduce risk of hip fractures. And cardiofitness  provides a unique measure of this combination of amount and pace of exercise on bone health. 

The Life Ahead exercise and cardiofitness model provides for valuing both amounts and pace of walking.  The expected Life Ahead values of these combinations have been integrated with the results of study B6 to obtain a valuation of the effect of walking on risk that should approximate the contributions of all combinations of amounts and pace of walking to probable risk of hip fracture. Results of this analysis not only fit results of study B6 but are consistent with the other studies of exercise B4 and B5.

Other contributions to cardiofitness should protect further against hip fracture. Study B6 also shows that the amounts of a person's standing can have a substantial effect on risk of hip fracture.  The Life Ahead exercise module also shows that those that stand and walk about much of each day will develop significantly improved cardiofitness.  Thus the present model forecast will include at least an approximate recognition of this as a factor. No research on the value of more intense exercise on hip fracture was found.  It seems likely that more extensive exercise would be helpful, but few older adults will find this more intense type of exercise acceptable.  Exercise such as swimming that puts less stress on leg, hip, and back function my be less beneficial for osteoporosis than is walking and standing. 

Studies B1 and B3 both show those who exercise more have fewer falls. And it is the falls of older people that lead to fractures.  It might intuitively be thought that more walking would increase risk of falls, but this does not seem to be true. Study B7 showed that a program of Tia Chi reduced the risk of falls by more than half.  Resistance training exercise has been extensively proposed for reducing risk of osteoporosis.  Study B2 did show that resistance training for the hip did improve bone density somewhat. But it seems likely that larger reductions in risk can be achieved and achieved more easily by walking programs.  And walking conveys the very substantial cardio-effective benefits for heart disease and cancer that is not usually provided as well by resistance type exercise. 

Exercise and particularly the type of exercise that produces cardiofitness emerges time and again in the research studies of nearly every major disease to be a key factor lowering risk. Avoiding hip fracture may not be a major reason that people should exercise more.  But it is another important reason why those that are old and particularly those that are very old should keep up doing this all-important protector of health and life as long as they can. .

Osteoporosis and use of Calcium:  By far the major diet factor proposed for reducing risk of osteoporosis is the intake of adequate calcium and the vitamin D that is needed for its proper use by the body. Despite a vast discussion of this, the actual verifying research on the value of calcium is far less convincing than desired.  Study E1 did confirm that the use of calcium tablets did reverse the long term decline of bone less at both hip and neck, and produced a net increase in density. Slightly better results were obtained when the calcium tablets were combined with more exercise.  But milk powder produced less benefit, and results of much research on osteoporosis and milk intake is less than impressive.

Study E3 is a meta analysis of results of 15 different studies of the effect of calcium intake on various fractures.  The results although positive were discouraging.  Like so many meta analyses, this one identified an average risk of a not-identified amount of calcium on diets starting with different amounts of calcium used for different but not-identified amounts of time. So the value of the produced statistics are limited.  But typical starting diets were of 700 mg of calcium to which 500 to 1000 mg of calcium was added for a typical time of only 2 years. This produced risk values of 0.77 for vertebral fractures and 0.86 for all other fractures, reductions in risk of only 23% and 14%. If the true benefits of calcium are time related they could produce major benefits if continued over 10 or more years.  But unfortunately this does not appear to be established.

Life Ahead does include a modest benefit for use of dietary calcium derived from this information.  The usual target for calcium from diet and supplements is 1,000 mg/day, but older people have been encouraged to considered 1,500 mg/day.  Inclusion of Vitamin D with the calcium is essential.  Usual dietary intake is around 500 mg/day, and thus a calcium supplement of at least 500-600 appears prudent for most men and women, and especially for all that are above age 60. But health interested persons should not assume that just taking calcium pills will prevent them from suffering osteoporosis.

Osteoporosis, Hip Fracture, and use of Female Hormones:    It has long been acknowledged that use of postmenopausal hormones by women reduces risk of hip fracture.  Studies D1, D2, and D3 in the table following confirm this   Study D1 found that high rates of  fracture occurred when women's measured estradiol was very low. But once amounts became measurable the rate of hip fracture dropped to 0.4 of that rate or 60% lower for both hip and vertebral fracture. Both of studies D2 and D3 found that hip fracture rates for use of post menopausal hormones were the same 0.4 rate of no hormone use for sedentary women that did little exercise. But each study noted that the hip fracture benefits from hormone use declined when used by physically active women.  Apparently hormones and physical activity appear to produce similar but partly duplicated benefits. 

Life Ahead now uses a model that combines risks from both hormones and exercise as cardiofitness to fit the research of studies D2 and D3.  This shows that women that are sedentary and do little exercise and have deficient cardiofitness obtain up to the 0.4 ratio or 60% benefit for hormone use.  But that this benefit for hormone use declines to less than 0.2 or a 20% benefit for those with good exercise and cardiofitness.  Because most women today and especially those much older that are at highest risk for hip fracture do not do much exercise, an average older woman should achieve about a 50% reduction in risk of hip fracture from use of postmenopausal hormones.  No adequate information was found for use of estrogen or estrogen projesterone combinations on risk of hip fractures.      

Some Other Factors and Osteoporosis:  A number of other factors have been cited as risks for osteoporosis and hip fractures.  But evidence on these is not now sufficient for an inclusion of risk in Life Ahead.  Family history probably as some effect on risk.  One study suggested a risk of 2 times for a mother that had a hip fracture, and another noted a risk of 1.6 times for the same. But the margins of error on these estimates were high, and this is insufficient evidence for a useful quantified risk in Life Ahead.  Another problem with family history risk is that risks of an earlier generation can be higher than that for a present generation, and this can lead to an incorrect family history association.

A number of studies relate Alcohol intake to risk of osteoporosis.  There is good agreement that excessive alcohol in amounts of 3 or more drinks per day is harmful, and such probably increase risk at least 50%.  But risks for 2 or fewer daily drinks appear to be either nil or perhaps even reduced.  One study cited an 0.8 risk (favorable) risk for 1-2 drinks per day.  Again, results of alcohol risks on all major diseases favor use of 1 drink per day a beneficial, but much more than this one per day does not appear beneficial when risks of all involved diseases are recognized.  Life Ahead computes a moderate added risk of osteoporosis for high alcohol consumption.   Use of Thyroid Hormone has been cited as increasing bone loss and increasing risk of fractures, but again research here is not sufficient for conclusion of a Life Ahead risk.

A seriously missing factor noted in this review of the research on osteoporosis is how various factors combine to improve and increase risks.  Exercise and female hormones are noted to be partly duplicative in their benefits. Do benefits from estrogen and calcium combine, or are the duplicative?  And do benefits from medications (see following) add to or simply replace effects of possible life style improvements?  More information on this appears needed.

See the Doctor:  Useful medications are available for reducing the risk of osteoporosis and of hip and other major fractures. Those often used can reduce risk of a major fracture by perhaps 50%.  This reduction is far from a preventative as risk of hip fractures can increase 20 times as people become much older. And  medications can have unwanted side effects.  Still,  all men and women and especially women should get a periodic bone density test as the move much past age 60 and consider the doctors advice if such tests suggest risk. Many doctors now feel that medications for osteoporosis still are seriously under-used. And as health-interested people move past ages of say 70 they should recognize the increasing risk of major bone fractures as a serious potential obstacle to obtaining the best length and quality of a remaining life.

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