Topics

Intro
Cigarette Smoke
Nicotine
Carbon Monoxide
Other Substances
Smoke and Bone
Bone Healing
Wound Healing
Osteonecrosis
Lower Back Pain
Arthritis
Dupuytrens
RSD (CRPS)
Summary
Bibliography

Smoke and Bone

After reaching peak bone mass at the age of 33, human bone loss occurs at a relatively fixed rate approximating 0.5 percent per year in women and 0.3 percent per year in men (Type II osteoporosis). At menopause, due to sudden estrogen deprivation, bone loss accelerates to 2 to 3 percent per year for the next 6 to 10 years (Type I osteoporosis), following which the rate of loss returns to its former, baseline level, 0.5 percent per year.20 84

At the age of 65, or 15 years postmenopause, bone mineral content varies; however most women have lost 33.5 percent of one-third of their bone mass, due to the combined effects of Type I and II osteoporosis. Men have lost 10 percent of bone mineral, due to Type II osteoporosis. This loss in bone mineral results in skeletal weakness and increased fracture rates in the distal radius, spine and hip. Women are particularly vulnerable, due to this increase in skeletal fragility and the greater likelihood of trauma since the female life span is five years greater than men.

Smoking presents added stress to the skeletal system by accelerating the loss of bone mineral in both men and women.45 60 99 100 102 The exact mechanism for this effect has never been determined with certainty. Slender women seem to be affected to a greater degree,14 21 however, body weight alone cannot adequately explain loss of bone mineral.35 45 48 55 86 101

Women who are smokers enter menopause, on the average, two years earlier than nonsmokers6 and, according to some investigators, lose bone mineral more rapidly after menopause than nonsmokers.45 56 Hopper, in a study of female twins, found evidence of increased bone resorption and high levels of FSH and LH which suggest relative estrogen deficiency.48 Several investigators have demonstrated an increase in estrogen degradation.21 51 67 65 113 114 Moreover, postmenopausal estrogen therapy is less effective in smokers, and higher doses may be required to achieve the desired result.51 55

Estrogen deficiency, however, does not explain the increase in osteoporosis found among men who smoke. Nicotine has an apparent toxic effect upon the osteoblast30 with a resultant decrease in bone formation.25 Calcitonin resistance has been induced by smoke extracts and has also been hypothesized as a cause for loss of bone mineral.46 A decrease in calcium absorption from the gut has also been implicated among smokers.56

Studies which investigate the relationship of smoking to loss of bone mineral are frequently confounded by other addictive behaviors. For example, heavy drinkers also tend to be heavy smokers.26 Nevertheless, smoking must be considered an important risk factor for the development of osteoporosis, and the summation of alcohol and nicotine addiction may accelerate bone loss even further. Slemenda believes that for those who both smoke and drink excessively, bone loss is approximately twice that of the normal rate of 0.3 percent to 0.4 percent per year, after age 33. This results in an eventual decrease in bone mass which is a full standard deviation (SD) beyond that which is normally anticipated at age 65. This significant decrease has serious implications for the older population since a decrease in bone density by one standard deviation approximately doubles the rate of fracture.99 100

Hopper and Seeman, in a study of twins, were able to reduce the impact of confounding factors. A significant decrease in bone density was observed in the smoking group with an obvious dose-response relationship. The results indicate that the twin with a 20 pack/year history of smoking developed a 5 to 10 percent greater decrease in bone density in a comparison to the nonsmoking twin.48 In vitro studies indicate that a 10 percent decrease in bone mineral confers a threefold increase in rate of fracture.17 A 10 percent deficit in mineral content represents a decrease in bone density of one full SD84 and over a period of 10 years, confers a 44 percent increase in rate of hip fracture.71

Unfortunately, this increase in skeletal fragility is accompanied by an increase in accident rate. Smokers are 1.5 times more likely to become involved in an automobile collision and 1.4 to 2.5 times more likely to be injured at work.76 87 The reasons for this propensity for accident is unclear. General weakness, with poorer balance and impaired neuromuscular performance, has been demonstrated among both active smokers and former smokers.76 In another study, smokers had a 4.1 fold increase in risk of tibial shaft fractures. Moreover, the fractures were more comminuted in the smoking population.59