Hyperkyphosis (increased curve) Associated With Increased Mortality in Older Women With Vertebral Fractures
June 2, 2009 - In older women with previous vertebral fractures, increased kyphosis can predict an increased risk for death, independent of the extent and severity of their underlying spinal osteoporosis, according to the results of a prospective cohort study reported in the May 19 issue of the Annals of Internal Medicine.
"It is well known that vertebral fractures are associated with an increased risk for death in older persons, but the explanation for this is unknown," write Deborah M. Kado, MD, MS, from the MacDonald Research Laboratory in Los Angeles, California, and colleagues. "Our previous work suggested that those with vertebral fractures were more likely to die of a pulmonary cause in particular, possibly because of vertebral fracture-induced changes in the thoracic kyphotic curvature that could detrimentally affect respiratory function."
They note that other studies have suggested that hyperkyphosis itself may be a risk factor for death. However, these studies could not explain whether the increased mortality risk came from increased thoracic curvature or the presence of clinically undetected vertebral fractures.
So Dr. Kado and her team sought to determine whether hyperkyphosis is associated with an increased risk for death independent of vertebral fractures and low bone mineral density. They evaluated a cohort of 610 participants from the Study of Osteoporotic Fractures, an ongoing prospective study of 9704 women 65 years and older recruited from Baltimore, Maryland; the Monongahela Valley, Pennsylvania; Minneapolis, Minnesota; and Portland, Oregon, from 1986 to 1988. Black women and all men were excluded because of the low expected incidence of fractures in these groups.
During the 2-year follow-up visit, 610 women (aged 67 - 93 years), representing all 4 clinic centers, were consecutively sampled to undergo flexicurve measurements to document the degree of thoracic curvature (kyphosis index) and dual-energy x-ray absorptiometry to measure total hip and spine bone mineral density. In addition, prevalent radiographic vertebral factures at baseline were defined by morphometry, and mortality was assessed during an average follow-up of 13.5 years. Also, all study participants completed a baseline questionnaire on education, medical history, and health behaviors, and completed a second visit questionnaire that included cigarette use.
End-of-study results showed that in age-adjusted models, each SD increase in kyphosis carried a 1.14-fold increased risk for death (95% confidence interval [CI], 1.02 - 1.27; P = .023). After adjusting for age and other predictors of mortality (including such osteoporosis-related factors as low bone density, moderate and severe prevalent vertebral fractures, and number of prevalent vertebral fractures), women with greater kyphosis were at increased risk for earlier death (relative hazard per SD increase, 1.15; 95% CI, 1.01 - 1.30; P = .029).
On stratification by prevalent vertebral fracture status, only women with prevalent fractures were at increased mortality risk from hyperkyphosis, independent of age, self-reported health, smoking, spine bone mineral density, number of vertebral fractures, and severe vertebral fractures (relative hazard per SD increase, 1.58; 95% CI, 1.06 - 2.35; P = .024).
"To date, most clinicians and patients attribute their hyperkyphotic posture to underlying osteoporosis; however, our data confirm that postural changes provide important clinical predictive ability that is not provided by markers of osteoporosis alone," write the study authors. "Our results suggest that women with vertebral fractures and hyperkyphosis are at greater risk for death than women with only vertebral fractures or only hyperkyphosis."
Limitations of the study include the participation of white women only, so the findings were not generalizable to men or to nonwhite women. In addition, because the morphometric reading of vertebral fractures was based on vertebral height ratios only, it may have led to misclassification of other causes of decrements in height ratios, such as Scheuermann's disease.
The correlation between kyphotic index and either the kyphotic angle or clinical measures of the distance from occiput to wall was also not known. "So clinically relevant comparisons are difficult to make," write the study authors. "However, each measure has been shown to have construct validity, and the flexicurve measure may even be superior to those that depend on specific vertebral edges, such as the more widely used Cobb angle."
Dr. Kado's team writes that the study also had several strengths. "First, this was a prospective study with substantial long-term and 95% complete follow-up over 13.5 years. Second, all women underwent standardized testing for underlying vertebral fractures; thus, we obviated a limitation of previous studies - inability to exclude underlying vertebral fractures as a mechanism of the association of hyperkyphosis and ill health."
They conclude, "Because it is readily observed and is associated with ill health in older persons, hyperkyphosis should be recognized as a geriatric syndrome - a 'multifactorial health condition that occurs when the accumulated effect of impairments in multiple systems renders a person vulnerable to situational challenges.' "
This study was supported by grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases and the National Institute on Aging. The study authors have disclosed no relevant financial relationships.
Ann Intern Med. 2009;150:681-687.
Although there are varying definitions of hyperkyphosis in older adults, there can be no doubt regarding its impact on health. In a review by Kado and colleagues, which was published in the September 4, 2007, issue of the Annals of Internal Medicine, the prevalence of hyperkyphosis in older adults was estimated to be between 20% and 40%. Although vertebral fractures are associated with a higher risk for hyperkyphosis, many patients with hyperkyphosis have no evidence of fracture. Hyperkyphosis has been associated with decreased pulmonary function, worse physical function, and a higher risk for both falls and fracture.
Hyperkyphosis has also been associated with an increased risk for death, particularly death related to pulmonary causes. However, previous research has not always accounted for other covariates that might also affect mortality rates. The current study addresses this issue.
- Study participants were part of the Study of Osteoporotic Fractures, which prospectively examined risks for fracture in community-dwelling women 65 years or older.
- Participants underwent a measure of kyphosis with the flexicurve instrument, which is a standard technique using a flexible measuring tape. Radiographs of the spine were also performed at baseline, and prevalent vertebral fractures were recorded.
- Researchers evaluated participants' demographic data, medical history, and health behaviors. Women also underwent measurements of body mass index and bone mineral density.
- The main outcome of the study was the association between the degree of kyphosis and mortality rate. This result was adjusted to account for covariates as described, including previous vertebral fracture. The mean follow-up period was 13.5 years.
- The study cohort included 610 women. The mean age of participants was 72.8 years, and 6.5% of the study cohort reported a history of vertebral fracture. Other than a reduced bone mineral density, women with a history of vertebral fracture had similar baseline characteristics vs women without vertebral fracture.
- 317 women died during follow-up. In age-adjusted models, each SD increase in the degree of kyphosis increased the relative hazard for mortality by a significant factor of 1.14.
- After full adjustment for other predictors of mortality plus bone mineral density and a history of vertebral fracture, the relative hazard for death for each increase in SD of kyphosis remained significant at 1.15.
- On further analysis, only women with prevalent vertebral fracture were at an increased risk for death related to hyperkyphosis. However, the number of vertebral fractures or the severity of vertebral fractures did not alter the effect of hyperkyphosis on the risk for death.
- The prevalence of hyperkyphosis in older adults is between 20% and 40%, and it is not always associated with vertebral fractures. Hyperkyphosis in older adults has been associated with decreased pulmonary function, worse physical function, and a higher risk for both falls and fracture.
- The current study suggests that hyperkyphosis is associated with a higher overall risk for mortality in women with a history of vertebral fracture.
As a Chiropractor in Concord it is my job to understand the relevance of the spine and the nervous system. Chiropractors have long known that interference to this nervous system can lead to sickness and disease. Now the research is proving what chiropractors have said all along.
Do not wait to become a statistic. Call Barton Family Chiropractic now at 685-2002.