Health-related quality of life measurements in elderly Canadians with osteoporosis compared to other chronic medical conditions: a population-based study from the Canadian Multicentre Osteoporosis Study (CaMos)
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- Sawka, A.M., Thabane, L., Papaioannou, A. et al. Osteoporos Int (2005) 16: 1836. doi:10.1007/s00198-005-1949-6
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The objective of this research was to determine the relative decrement in health-related quality of life, as measured by the health utilities index mark 3 (HUI3), in osteoporosis compared to other chronic medical conditions. The impact of chronic medical conditions other than osteoporosis on HUI3 measurements had been previously established in the 1996/1997 Canadian National Population Health Survey (NPHS). The Canadian Multicentre Osteoporosis Study (CaMos) is a national population-based study in which regional participants were randomly recruited, regardless of presence of osteoporosis. We analyzed data from participants aged ≥65 years who completed a baseline HUI3 questionnaire and provided information on their medical history (n=3,750). We determined the age- and gender-adjusted mean decrement in HUI3 for several chronic medical conditions, including osteoporosis. The mean changes in HUI3 adjusted for age and gender (with 95% confidence intervals) were as follows: arthritis −0.10 (−0.11, −0.09), chronic obstructive pulmonary disease (COPD) −0.07 (−0.09, -0.05), diabetes mellitus −0.05 (−0.08, −0.03), heart disease −0.06 (-0.08, −0.04), hypertension −0.02 (-0.03, −0.01), and osteoporosis −0.08 (−0.11, −0.06), respectively (model r2=0.17; P<0.0001). These findings were comparable to those observed in the NPHS, with the exception of osteoporosis, which had not been previously studied in this fashion. The decrement in HUI3 score seen in participants with osteoporosis was comparable to that observed in other chronic medical conditions, such as arthritis, COPD, diabetes mellitus or heart disease.
KeywordsHealth-related quality of lifeHealth utilities indexOsteoporosis
Osteoporosis is “a skeletal disorder characterized by compromised bone strength predisposing a person to an increased risk of fracture” . Osteoporosis is common; the estimated prevalence rate of vertebral fractures in Canadian men and women aged 50 years and older is approximately 20% . Fractures of the hip and spine as a consequence of osteoporosis have been associated with increased morbidity, mortality, institutionalization and length of hospital stay [3, 4, 5, 6, 7, 8, 9, 10]. Osteoporosis-related outcomes have been studied in the Canadian Multicentre Osteoporosis Study (CaMos), which is a prospective, national, population-based cohort study involving nine sites across Canada (St. John’s, Halifax, Quebec City, Kingston, Toronto, Hamilton, Saskatoon, Calgary, and Vancouver) . The CaMos group has previously reported that presence of a prevalent main or minimal trauma fracture was negatively associated with measurements of health-related quality of life (HRQL) as measured by the health utilities index 2 and 3 (HUI2 and HUI3) . However, the relative decrement in HUI3 score attributed to a diagnosis of osteoporosis, compared to other chronic medical conditions, is unknown.
The primary objective of this study was to determine the mean decrement in HUI3 score attributable to osteoporosis, relative to other medical conditions, using baseline data from participants aged 65 years of age and older in the CaMos. The secondary objective was to compare the disease-related regression coefficients from our model to those obtained in the 1996/1997 Canadian National Population Health Survey (NPHS) , as a form of external validation of our results.
Participants in the CaMos were randomly recruited, beginning in 1995, from a list of residential telephone numbers within a 50-km radius of each of the nine study centers . Participants were recruited regardless of any known diagnosis of osteoporosis. The initial cohort included 9,423 people, aged 25 and older (stratified by age and gender) . All participants were questioned at baseline about their medical history. We examined data from all CaMos participants aged 65 years and older who completed a baseline HUI3 questionnaire and provided information on their medical history for the diagnoses of interest. The diagnoses of interest included: osteoporosis, arthritis (osteoarthritis or rheumatoid arthritis), chronic obstructive pulmonary disease (COPD), diabetes mellitus (type 1 or type 2), heart disease (labeled as “heart attack”) and hypertension.
In the current analysis, if individuals indicated that they did not know if they had a medical condition or did not respond to a question about presence of a medical condition, they were coded as non-responders for the condition in question. In the case of arthritis, participants were asked in two separate questions whether they had osteoarthritis and if they had rheumatoid arthritis. If one of the responses to the questions about arthritis was positive, the participant was coded as having arthritis. If both of the responses were negative, the participant was coded as not having arthritis. If a response to either of these questions pertaining to arthritis was missing, lack of a complete response was noted. We did not perform any review of outside medical records or contact the primary care physician to ascertain if the conditions in question had been diagnosed.
A baseline HUI3 questionnaire was administered to all individuals participating in the CaMos. The HUI3 is a generic, preference-based, health classification tool that consists of eight attributes: vision, hearing, speech, ambulation, dexterity, emotion, cognition, and pain [14, 15, 16]. The levels of each attribute vary from highly impaired to normal (with five or six levels per attribute) . The original respondents whose data was used to develop the HUI3 scoring system were asked to evaluate perfect health, “most disabled” states, a death state, and three marker states with mild, moderate, and severe morbidity burdens . The preferences of these original subjects were used in defining the scoring systems for each attribute, and data from multiple attributes were combined using principles of the von-Neumann–Morgenstern expected utility theory . A HUI3 multi-attribute score may vary from −0.36 (all attributes at the lowest functional level) to 1.00 (perfect health), where a score of zero represents a state equivalent to death [14, 15, 16]. A negative HUI3 score corresponds to a “most disabled” health state, which was considered worse than death by the majority of respondents whose data were used to develop the original HUI3 scoring system . In other words, most respondents whose data were used to develop the HUI3 instrument preferred the state of being dead to being “most disabled” . We calculated a multi-attribute HUI3 score for each individual who completed the survey .
Participants’ demographics and reported medical conditions were summarized using mean, standard deviation (SD), or the minimum (min) and the maximum (max) for continuous variables and number (percent) for categorical variables. A linear regression model predicting mean difference in HUI3 score included the following variables: age, gender, osteoporosis, arthritis, COPD, diabetes mellitus, heart disease, and hypertension. A linear regression model was performed using SPSS version 10, in which all variables are simultaneously forced into the model. The results are expressed as estimates of model parameters and corresponding 95% confidence interval (CI). Models were evaluated for goodness-of-fit using the coefficient of determination r2 and corresponding test for model significance. Statistical significance was set a priori at alpha=0.05, two-tailed.
As a test of external validity of the age- and gender-adjusted disease-related regression coefficients, we compared our findings with those for similar conditions reported in cycle 2 of the Canadian NPHS of 1996/1997 for the same age group  and chronic medical conditions self-reported in the NPHS . Of note, osteoporosis was not a chronic condition examined in the HUI3 analysis of the NPHS. We checked the robustness of the CaMos-based linear regression model by performing a sensitivity analysis, in which non-response to disease-related questions was considered as a negative response (i.e. absence of the condition).
Of the 4,550 participants aged ≥65 years recruited in the CaMos, 4,495 completed a baseline HUI3 questionnaire and were eligible for inclusion in the analysis [1,226 men (27%) and 3,269 women (73%), mean age 73.0 years, SD 6.1 years]. The mean HUI3 score for these participants was 0.78 (SD 0.23, min to max = −0.32 to 1.0). Of these 4,495 participants, 3,750 (1,034 men and 2,716 women) provided information on presence or absence of each of the diseases of interest, including osteoporosis, arthritis, COPD, diabetes mellitus, heart disease, and hypertension; data from these individuals were included in the linear regression model predicting change in HUI3 scores. Of these 3,750 individuals, the number who reported being aware of having a chronic medical condition was as follows: osteoporosis 421 (11%), arthritis 1,675 (45%), COPD 410 (11%), diabetes mellitus 352 (9%), heart disease 396 (11%), hypertension 1,470 (39%).
The mean HUI3 scores for groups included in the regression analysis (not adjusted for age or gender)
All 3,750 individuals included in the regression analysis
Individuals with chronic obstructive pulmonary disease (n=410)
Individuals with diabetes mellitus (n=352)
Individuals with heart disease (n=396)
Individuals with hypertension (n=1,470)
Individuals with arthritis (n=1,675)a
Individuals with osteoporosis (n=421)
Table 2. Comparison of age- and gender-adjusted difference in HUI3 score for persons 65 years of age and older observed in the 1996/1997 Canadian National Population Health Survey and CaMos for several common chronic medical conditions
Chronic medical condition
Chronic obstructive pulmonary disease (“chronic bronchitis/emphysema” in NPHS)
-0.09 (-0.13, -0.05)
-0.07 (-0.09, -0.05)
-0.06 (-0.09, -0.03)
-0.05 (-0.08, -0.03)
Heart disease (“heart attack” in CaMos)
-0.06 (-0.08, -0.03)
-0.06 (-0.08, -0.04)
Hypertension (“high blood pressure” in NPHS)
0.00 (-0.02, 0.02)
-0.02 (-0.03, -0.01)
Arthritis (“osteoarthritis or rheumatoid arthritis” in CaMos, “arthritis/rheumatism” in NPHS)
-0.08 (-0.10, -0.06)
-0.10 (-0.11, -0.09)
-0.08 (-0.11, -0.06)
In a sensitivity analysis we assumed that non-response to a question pertaining to presence of a chronic medical condition meant absence of that condition. Of the 4,495 participants who completed a HUI3 questionnaire, the number who did not respond to questions pertaining to presence of respective medical conditions were as follows: osteoporosis 98 (2%), arthritis 239 (5%), COPD 415 (9%), diabetes mellitus 1 (0.02%), heart disease 27 (0.6%), hypertension 16 (0.4%). When these individuals were included in the analysis, the mean differences (95% CI) in HUI3, adjusted for age and gender, were as follows: arthritis −0.09 (−0.10, −0.08), COPD −0.07 (−0.09, −0.05), diabetes mellitus −0.07 (−0.09, −0.05), heart disease −0.05 (−0.07, −0.03), hypertension −0.02 (−0.04, −0.01), and osteoporosis −0.09 (−0.11, −0.07), respectively (model r2=0.16; P<0.0001). Thus, when these individuals were assumed not to have the conditions in question, the mean changes in age- and gender-adjusted HUI3 scores (including model goodness-of-fit statistics) were almost identical to the original analysis. We therefore considered our findings robust.
Osteoporosis and resultant fractures are common occurrences in men and women aged 50 years and older in Canada . Furthermore, osteoporotic fractures are known to reduce HRQL significantly in men and women of this age group . However, it has been unclear how much a diagnosis of osteoporosis reduces HRQL, relative to other chronic medical conditions. We determined that the age- and gender- adjusted decrement in quality of life, as measured by the HUI3 score, was similar to that of other chronic medical conditions, such as arthritis, COPD, diabetes mellitus, and heart disease in Canadians 65 years of age and older. Of note, some experts consider a change in HUI3 score of 0.03 to be a “minimal clinically important difference” ; the decrement in HUI3 that was observed with osteoporosis in CaMos was approximately triple this value. Thus, the decrement in HRQL observed in osteoporosis should be considered clinically significant. The estimates of disease-related decrements in HUI3 score for conditions other than osteoporosis were externally validated by comparison with the results of the 1996/1997 NPHS .
There are several limitations to this study. Only community-dwelling participants living within 50 km of a Canadian study center were eligible for study . Thus, individuals in rural and remote areas, or the institutionalized elderly, were not studied. We also recruited more women than men by design . Furthermore, the study was restricted to a Canadian population. Thus, the external generalizability of our findings to other countries is uncertain. Although patients with osteoporosis were not selectively encouraged to participate in this study, recruited individuals were aware that the purpose of the study was to evaluate osteoporosis in the Canadian population. Although it is possible that persons who had osteoporosis or who felt they were at risk for the condition selectively chose to participate, a comparison of CaMos participants with individuals who chose not to participate did not suggest any such selection bias, except for possibly in a small minority of very elderly subjects aged 80 years or older . We examined only self-reported disease states, which can be limited by variable accuracy . Furthermore, many participants did not know if they had been diagnosed with the medical conditions studied. We did not review outside medical records to confirm presence of chronic medical conditions.
We also had no information on the HRQL, or the disease states, of the individuals who chose not to participate in either survey. Non-participants may have felt too physically, mentally, or emotionally unwell to participate in such surveys. Our test of external validity, by comparing our findings with those observed in the NPHS, was limited by differences in wording of questions pertaining to disease states and differences in population sampling. Another limitation of our study is that we did not examine the effect of presence of one or more respective co-morbidities on the decrement in HUI3 attributable to other co-morbidities. Reasons why we could not systematically explore such statistical interactions included (a) lack of statistical power (given the low prevalence of some conditions and the large number of interactions possible); (b) inability to externally validate our findings using the NPHS report (as such an interaction analysis was not reported in the NPHS study).
The HUI3 instrument is generic, and a global score consists of multiple attributes, some of which may not be directly relevant to the condition of osteoporosis (for example, hearing). However, the International Osteoporosis Foundation has recommended that this generic, preference-based measure be used in clinical trials and observational studies of osteoporosis . Of note, a cross-sectional survey, such as the one presented herein, captures information at only one point in time in a disease state. In the case of osteoporosis, HRQL would be expected to vary with the presence of a recent acute fracture or development of chronic pain secondary to multiple fractures with deformity.
Similarly, in the case of other medical conditions, HRQL may deteriorate acutely with exacerbation of the disease (such as a pulmonary infection in the case of COPD, a recent episode of acute coronary syndrome with “heart disease”, or recent acute inflammation of a joint in the case of arthritis). Thus, a one-time, cross-sectional, survey cannot capture the disease burden in terms of HRQL over the entire course of a disease or a lifetime. Long-term prospective data, including measurements of HRQL at multiple points in time, are required in order to estimate better the disease burden of a chronic illness for an individual and the population. Nevertheless, in the absence of such long-term, prospective data, cross-sectional data, as presented herein, may be used in the interim for development of health policy. We will learn more about the long-term impact of osteoporosis when the 5- and 10-year prospective follow-up data from the CaMos become available.
Although cross-sectional HRQL data have been examined in the CaMos, further research is needed to examine the long-term impact of osteoporosis on HRQL. Given the magnitude of decrement of HUI3 measurements seen with osteoporosis in our analysis, it is important that this condition be included in future population-based studies of HRQL (such as the NPHS). In CaMos we are currently prospectively collecting data for future examination of the long-term impact of osteoporosis and incident fractures on the HRQL.
The Canadian Multicentre Osteoporosis Study was funded by the Senior’s Independent Research Program, through the National Health Research and Development Program of Canada (project no. 6605-4003-OS); the Medical Research Council of Canada, MRC-PMAC Health Program; Merck Frosst Canada, Inc.; Eli Lilly Canada, Inc.; Procter and Gamble Pharmaceuticals Canada, Inc.; Aventis Pharma Inc.; Novartis Inc.; and the Dairy Farmers of Canada. We would like to thank the CaMos Publication Committee for thoughtful reviews of our analysis plan and results.