Epidemiology of gout: is the incidence rising?

OBJECTIVE

To determine whether the incidence of gout is higher in 1995-1996 compared to 1977-1978.

METHODS

Using the Rochester Epidemiology Project computerized medical record system, all potential cases of acute gout in the city of Rochester, Minnesota during the time intervals of 1977-1978 and 1995-1996 were identified. The complete medical records of all potential cases were screened and all who fulfilled the 1977 American College of Rheumatology proposed criteria for gout were included as incidence cases. Demographic data, body mass index, clinical presentation, and associated comorbid conditions were abstracted. The overall and age-gender adjusted incidence rates from the 2 cohorts were calculated and compared.

RESULTS

A total of 39 new cases of acute gout were identified during the 2 year interval 1977-1978 representing an age and sex-adjusted annual incidence rate of 45.0/100,000 (95% CI: 30.7, 59.3). For the interval 1995-1996, 81 cases were diagnosed, representing an annual incidence rate of 62.3/100,000 (95% CI: 48.4, 76.2). There was a greater than 2-fold increase in the rate of primary gout (i.e., no history of diuretic exposure) in the recent compared to the older time periods (p = 0.002). The incidence of secondary, diuretic related gout did not increase over time (p = 0.140).

CONCLUSION

Our results indicate that the incidence of primary gout has increased significantly over the past 20 years. While this increase might be a result of improved ascertainment of atypical gout, it may also be related to other, as yet unidentified, risk factors.

Predictors of infection in rheumatoid arthritis

OBJECTIVE

Patients with rheumatoid arthritis (RA) have been shown to have an increased susceptibility to the development of infections. The exact causes of this increased risk are unknown, but may relate to immunologic disturbances associated with the disease or to the immunosuppressive effects of agents used in its treatment. This study was undertaken to identify predictors of serious infections among patients with RA. Identification of such factors is the necessary first step in reducing the excess risk of infection in RA.

METHODS

Members of a population-based incidence cohort of Rochester, Minnesota residents ages >or=18 years, who had been diagnosed with RA between 1955 and 1994, were followed up longitudinally through their complete medical records until January 1, 2000. We examined potential risk factors for the development of all objectively confirmed (by microbiology or radiology) infections and for infections requiring hospitalization. Potential risk factors included RA severity measures (rheumatoid factor positivity, elevated erythrocyte sedimentation rate, extraarticular manifestations of RA, and functional status), comorbidities (diabetes mellitus, alcoholism, and chronic lung disease), and other risk factors for infection (presence of leukopenia, smoking). Predictors were identified using multivariate time-dependent Cox proportional hazards modeling.

RESULTS

The 609 RA patients in the cohort had a total followup time of 7,729.7 person-years (mean 12.7 years per patient). A total of 389 patients (64%) had at least 1 infection with objective confirmation, and 290 (48%) had at least 1 infection requiring hospitalization. Increasing age, presence of extraarticular manifestations of RA, leukopenia, and comorbidities (chronic lung disease, alcoholism, organic brain disease, and diabetes mellitus), as well as use of corticosteroids, were strong predictors of infection (P < 0.004) in both univariate and multivariate analyses. Notably, use of disease-modifying antirheumatic drugs was not associated with increased risk of infection in multivariate analyses, after adjustment for demographic characteristics, comorbidities, and disease-related variables.

CONCLUSION

We identified a number of strong predictors of infections in a population-based cohort of patients with RA. These results can be used to prospectively identify high-risk patients, who may benefit from closer followup and implementation of preventive strategies.

Frequency of infection in patients with rheumatoid arthritis compared with controls: a population-based study

OBJECTIVE

A high frequency of infections complicating rheumatoid arthritis (RA) has been described in reports of case series. This retrospective longitudinal cohort study was undertaken to compare the frequency of infections in a population-based incidence cohort of RA patients with that in a group of individuals without RA from the same population.

METHODS

RA patients included all members of an incidence cohort of Rochester, Minnesota residents ages >or=18 years who were first diagnosed as having RA between 1955 and 1994. One age- and sex-matched subject without RA was selected for each patient with RA. Study subjects were followed up by review of their entire medical record until death, migration from the area, or study end (January 1, 2000), and details of all documented infections, along with information on potential risk factors for infection, were recorded. Hazard ratios for infections were estimated using stratified Andersen-Gill proportional hazards models, with adjustment for potential confounders.

RESULTS

The 609 RA patients and 609 non-RA study subjects (mean age 58.0 years; 73.1% female) were followed up for a mean of 12.7 years and 15.0 years, respectively, reflecting higher mortality among the group with RA. Hazards ratios for objectively confirmed infections, infections requiring hospitalization, and any documented infection in patients with RA were 1.70 (95% confidence interval [95% CI] 1.42-2.03), 1.83 (95% CI 1.52-2.21), and 1.45 (95% CI 1.29-1.64), respectively, after adjustment for age, sex, smoking status, leukopenia, corticosteroid use, and diabetes mellitus. Sites of infection with the highest risk ratios were bone, joints, skin, soft tissues, and the respiratory tract.

CONCLUSION

In this study, patients with RA were at increased risk of developing infections compared with non-RA subjects. This may be due to immunomodulatory effects of RA, or to agents with immunosuppressive effects used in its treatment.

Long-term fracture risk in patients with Crohn's disease: a population-based study in Olmsted County, Minnesota

BACKGROUND & AIMS

Osteoporosis is common in patients with Crohn's disease, but less is known about their risk of actual fractures.

METHODS

The medical records of all 238 Olmsted County, Minnesota, residents diagnosed with Crohn's disease between 1940 and 1993 were reviewed for evidence of subsequent fractures compared with a control group of county residents matched by age and sex. The risk ratio of fracture in patients relative to controls was estimated using the Cox proportional hazards regression model. The cumulative incidence of fracture following diagnosis was estimated using the Kaplan-Meier method.

RESULTS

Sixty-three patients had 117 different fractures. The cumulative incidence of any fracture from the time of diagnosis onward was 36% at 20 years versus 32% in controls (P = 0.792). Compared with controls, the overall risk ratio for any fracture was 0.9 (95% confidence interval [CI], 0.6-1.4), whereas the relative risk for an osteoporotic fracture was 1.4 (95% CI, 0.7-2.7). The risk ratio for thoracolumbar vertebral fracture was 2.2 (95% CI, 0.9-5.5). Cox proportional hazards regression identified only age as a significant clinical predictor of fracture risk (hazard ratio per 10-year increase in age, 1.3; 95% CI, 1.1-1.5). Specifically, use of corticosteroids and surgical resection did not predict risk of fracture among these unselected patients with Crohn's disease from the community.

CONCLUSIONS

In this population-based inception cohort of patients with Crohn's disease, the risk of fracture was not elevated relative to age- and sex-matched controls.

Trends in the incidence of polymyalgia rheumatica over a 30 year period in Olmsted County, Minnesota, USA

OBJECTIVE

To determine time trends in the incidence and survival of polymyalgia rheumatica (PMR) over a 30 year period in Olmsted County, Minnesota, USA.

METHODS

Using the unified medical record linkage system of the Rochester Epidemiology Project, we identified all incident cases of PMR among residents of Olmsted County, MN, between January 1, 1970, and December 31, 1999. Incidence rates were estimated and age- and sex-adjusted to the 1990 US white population. The annual incidence rates were graphically illustrated using a 3 year centered moving average. A Poisson regression model was used to evaluate predictors of PMR incidence. Survival rates were computed and compared with the expected rates in the population.

RESULTS

There were 378 incident cases of PMR during the 30 year study period. Of these 66.6% were female and the mean age at incidence was 72.8 years. The overall age and sex adjusted annual incidence of PMR per 100,000 population aged > or = 50 years was 58.7 (95% CI 52.8,64.7). Incidence rates increased with age in both sexes, but in women, unlike in men, incidence fell after age 80. The incidence rates varied over the period of observation, but no significant trends over time were found. In the multivariable analysis, sex (p = 0.023), age (p < 0.001), and age2 (p < 0.001), but not calendar year (p = 0.24) were significant predictors of incidence. Survival among individuals with PMR was not significantly different from that expected in the population (p = 0.06).

CONCLUSION

The incidence of PMR has remained relatively stable over the past 30 years.

Osteopenia in adults with a history of juvenile rheumatoid arthritis. A population based study

OBJECTIVE

To determine the extent of osteopenia in a population based cohort of adults with a history of juvenile rheumatoid arthritis (JRA).

METHODS

The Rochester Epidemiology Project database was used to identify all cases of JRA diagnosed among Rochester, Minnesota residents under the age of 16 years between January 1, 1960, and December 31, 1993. Thirty-two of the 57 adult patients in this population based cohort (ages 19-53 years, mean 35) participated in this study. Average length of followup from the time of diagnosis was 27.1 years (median 26.9, range 7.7-39.1). Dual energy x-ray absorptiometry scans were used to assess bone density of the lumbar spine, hip, distal one-third radius, and whole body. In addition, a number of variables that influence bone mass were analyzed.

RESULTS

Although many participants had T scores within the normal range (T score > -1) at all measured sites, 41% (n = 13) were osteopenic (T score < or = -1) at either the lumbar spine or femoral neck. Twenty-eight percent (n = 9) had T scores < or = -1 in the lumbar spine (p = 0.058 relative to expected). Thirty-two percent (n = 10) had T scores < or = -1 in the femoral neck (p = 0.012 relative to expected). Several variables were significantly (p < 0.05) associated with low bone density in this cohort of adults with a history of JRA, including: (1) revised Steinbrocker functional class > or = 2 during adolescence, indicating poorer physical functioning; (2) lack of participation in organized sports during adolescence (a surrogate measure of physical activity); (3) tobacco use during adolescence; and (4) lower calcium intake during adolescence.

CONCLUSION

Although many adults with a history of JRA have normal bone density, a substantial subset are osteopenic, placing them at increased risk of fractures later in life. This observation is particularly striking given the predominance of patients with pauciarticular JRA in this population based group. We identified several variables associated with osteopenia in this cohort. Further work is needed to identify those patients with JRA who may benefit from aggressive therapy targeted at preventing the longterm morbidity associated with osteopenia.

Risk factors for the development of psoriatic arthritis: a population based nested case control study

OBJECTIVE

To identify factors influencing the development of psoriatic arthritis (PsA) in a population-based, inception cohort of psoriasis (PS) patients.

METHODS

Using the population-based data resources of the Rochester Epidemiology Project. which ensures virtually complete ascertainment of all clinically defined conditions, we previously identified all incident cases of PsA and prevalent cases with PS from 1/1/1982 to 12/21/1991. In this nested case-control study, we assessed potential factors influencing the development of PsA in this cohort using medical record and patient survey information. Each case of PsA was matched with 2 PS controls on age, gender and PS duration/date of onset. Factors influencing the development of PsA were identified, adjusting for the influence of other variables using conditional logistic regression for medical record data and logistic regression for survey data.

RESULTS

Sixty incident PsA cases were matched with 120 controls with PS. The median age at onset of PS was 31.7 (3.0-78.3) years, and 49% of subjects were male. There were 67% (n = 40) survey responders among cases and 48% (n = 58) among controls. Corticosteroids were used by 10 cases and 6 controls in the 2 years prior to onset of PS through to the development of PsA, and increased the risk of developing PsA (odds ratio 4.33, 95% CI = 1.34-14.02). Pregnancy occurred in 2 cases and 12 controls in the same period, and decreased the risk of developing PsA (odds ratio 0.19, 95% CI = 0.04-0.95). These associations remained significant after adjusting for the influence of gender, age, and duration of psoriasis.

CONCLUSION

Corticosteroid use and pregnancy, both of which modulate the immune response, may influence the development of PsA in patients with PS.

Trends in incidence and mortality in rheumatoid arthritis in Rochester, Minnesota, over a forty-year period

OBJECTIVE

To determine time trends in the epidemiology of rheumatoid arthritis (RA) in a population-based cohort.

METHODS

An inception cohort of residents of Rochester, Minnesota > or = 18 years of age who first fulfilled the American College of Rheumatology 1987 criteria between January 1, 1955 and December 31, 1994 (applied retrospectively, as appropriate) was assembled and followed up until January 1, 2000. Incidence rates were estimated and were age- and sex-adjusted to the 1990 white population of the US. A birth cohort analysis was performed, and survival rates over time were examined.

RESULTS

The incidence cohort comprised 609 patients, 445 (73.1%) of whom were female and 164 (26.9%) were male, with a mean age at incidence of 58.0 years. The overall age- and sex-adjusted annual incidence of RA among Rochester, Minnesota, residents > or = 18 years of age was 44.6/100,000 population (95% confidence interval 41.0-48.2). While the incidence rate fell progressively over the 4 decades of study, from 61.2/100,000 in 1955-1964, to 32.7/100,000 in 1985-1994, there were indications of cyclical trends over time. Birth cohort analysis showed diminishing incidence rates through successive cohorts following a peak in the 1880-1890 cohorts. Incidence rates increased with age until age 85, but peaked earlier in women than in men. The survival rate in RA patients was significantly lower than the expected rate in the general population (P < 0.001), and no improvement was noted over time.

CONCLUSION

The secular trends demonstrated in this study population, including the progressive decline in the incidence of RA over the last 40 years, suggest that an environmental factor may play a role in the etiology of RA.

Osteoporosis intervention following distal forearm fractures: a missed opportunity?

BACKGROUND

Fractures are a manifestation of osteoporosis, but therapeutic interventions to reduce the risk of recurrent fractures are not widespread.

OBJECTIVE

To identify predictors of osteoporosis treatment in postmenopausal women following distal forearm fracture.

METHODS

This population-based retrospective cohort study included all postmenopausal women, 45 years or older, residing in Olmsted County, Minnesota, who sustained a distal forearm fracture due to minimal trauma (a fall from standing height or under) in 1993 to 1997. Complete medical records were reviewed for each subject and Cox proportional hazards regression was used to evaluate the relationship of baseline demographic and clinical characteristics to therapeutic interventions for osteoporosis within 12 months following the fracture.

RESULTS

A total of 343 women with a mean age of 70.5 years had a minimal trauma distal forearm fracture. Within 12 months, 83% had seen a nonorthopedic physician. Of these, 17% had a pharmacologic osteoporosis intervention and the 12-month actuarially estimated cumulative incidence of any intervention was 18% (95% confidence interval [CI], 14%-22%). In a multivariate analysis, treatment was more likely to be offered to those with a prior diagnosis of osteoporosis (relative risk [RR], 2.08; 95% CI, 1.21-3.58), previous distal forearm fracture (RR, 2.38; 95% CI, 1.30-4.34), or history of cigarette smoking (RR, 1.86; 95% CI, 1.11-3.12).

CONCLUSIONS

Effective osteoporosis interventions are underutilized among postmenopausal women who experience an osteoporotic fracture. Further work is needed to overcome barriers to optimal osteoporosis management in these women who are at high risk for future complications of osteoporosis.

Occurrence of extraarticular disease manifestations is associated with excess mortality in a community based cohort of patients with rheumatoid arthritis

OBJECTIVE

To investigate the occurrence of extraarticular manifestations (ExRA) in a well defined community based cohort of patients with rheumatoid arthritis (RA), and to examine their effect on mortality.

METHODS

Using the resources of the Rochester Epidemiology Project, a retrospective medical record review was conducted of a cohort of 424 cases of RA in Olmsted County, MN, USA, diagnosed during the period 1955-1985. These cases had been classified using the American College of Rheumatology 1987 criteria for RA. Patients were followed 1955-1998 (median followup 14.8 yrs; range 0.2-42.8 yrs), and incident ExRA manifestations were recorded according to predefined criteria. Data on comorbidities were extracted using the definitions of the Charlson comorbidity index. Survival was compared to the general population using Kaplan-Meier estimates.

RESULTS

ExRA occurred in 169 patients, corresponding to an incidence rate of 3.67/100 person-yrs. Compared to the general population, survival among patients with RA was decreased. Survival among patients with ExRA was markedly decreased compared to the general population and to patients without ExRA (p < 0.001). A particularly poor prognosis was noted in a subgroup of 63 patients (incidence rate 1.04/100 person-yrs) who fulfilled predefined criteria for severe ExRA (i.e., vasculitis, pericarditis, pleuritis, and/or Felty's syndrome). For RA patients who did not fulfill these criteria, there was no significant increase of mortality (p = 0.09). In a multivariate model of mortality, including age, sex, and the presence of known comorbidities, the presence of one or more of these ExRA was the strongest predictor of mortality.

CONCLUSION

In this first community based study of extraarticular manifestations in RA, virtually all the excess mortality occurred in a subgroup of patients with severe extraarticular disease, suggesting that extraarticular disease is the major predictor of mortality in patients with RA.

A population based assessment of the use of orthopedic surgery in patients with rheumatoid arthritis

OBJECTIVE

To describe the use of orthopedic surgery, including joint replacement surgery, in a well defined population based cohort of patients with rheumatoid arthritis (RA) and to identify characteristics that predict such use.

METHODS

A retrospective medical record review was performed of cases of RA incident in Rochester, MN, during the years 1955-85. Patients were followed until 1998. All joint surgeries were recorded, including joint reconstructive surgeries, total joint arthroplasty (TJA), and other joint reconstructive procedures (JRP) such as tendon transfers and resections, joint fusions, and surgeries for fractures and infections involving joints.

RESULTS

Of the total 424 RA incident cases, 148 (34.9%) patients underwent one or more (maximum of 20/patient) surgical procedures involving joints during their followup (median 14.8 yrs, range 0.2-42.8 yrs). Overall, this RA cohort had 9.7 surgeries per 100 person-yrs of followup. The estimated cumulative incidence of surgical procedures for RA at 30 yrs was 52.7% +/- SE 4.2. Surgeries for arthritis related joint disease of RA included: primary TJA 76 patients (31.3 +/- 4.1); JRP joint fusion 78 patients (29.4 +/- 3.5); JRP soft tissue 92 patients (29.8 +/- 3.3); and cervical spine fusion one patient. Non-RA (trauma and other) joint surgeries included TJA 26 patients (13.5 +/- 3.4) and arthrotomy for septic arthritis 8 patients (2.4 +/- 0.9). Based on Cox proportional hazards regression, the risk of having a disease related joint surgery for RA is increased in patients who are younger (p < 0.001), have positive rheumatoid factor (p = 0.01), and those with rheumatoid nodules (p < 0.001). There was a borderline significant increase in the risk of first joint surgery in women (p = 0.09). Women also had significantly more joint surgeries (11.5/100 person-yrs) than men (4.9/100 person-yrs; p < 0.001). Survival of patients who had surgery for RA related joint disease was similar to those who did not.

CONCLUSION

This is the first population based assessment of joint surgeries performed in patients with RA. Reconstructive surgeries were common, and women had significantly more surgeries than men. Survivorship among patients with RA undergoing surgeries was similar to that of the RA patient population at large.

Direct medical costs attributable to osteoporotic fractures

Osteoporotic fractures are a major cause of morbidity in the elderly, the most rapidly growing segment of our population. We characterized the incremental direct medical costs following such fractures in a population-based cohort of men and women in Olmsted County, Minnesota. Cases included all County residents 50 years of age and older with an incident fracture due to minimal or moderate trauma between January 1, 1989 and January 1, 1992. For each case, a control of the same age (+/- 1 year) and sex who was attended in the local medical system in the same year was identified. Total incremental costs (cases - controls) in the year after fracture were estimated. Unit costs for each health service/procedure were obtained through the Mayo Cost Data Warehouse, which provides a standardized, inflation-adjusted estimate reflecting the national average cost of providing the service. Regression analysis was used to identify factors associated with incremental costs. There were 1263 case/control pairs; their average age was 73.8 years and 78% were female. Median total direct medical costs were $761 and $625, respectively, for cases and nonfracture controls in the year prior to fracture, and $3884 and $712, respectively, in the year following fracture. The highest median incremental costs were for distal femur ($11756) and hip fractures ($11241), whereas the lowest were for rib fractures ($213). Although hip fractures resulted in more incremental cost than any other fracture type, this amounted to only 37% of the total incremental cost of all moderate-trauma fractures combined. Regression analyses revealed that age, prior year costs and type of fracture were significant predictors of incremental costs (p<0.03 for all comparisons). The incremental costs of osteoporotic fractures are therefore substantial. Whereas hip fractures contributed disproportionately, they accounted for only one-third of the total incremental cost of fractures in our cohort. The use of incremental costs in economic analyses will provide a more accurate reflection of the true cost-effectiveness of osteoporosis prevention.

Value of immunological markers in predicting responsiveness to influenza vaccination in elderly individuals

Elderly individuals are at high risk for morbidity and mortality when infected with influenza virus. Vaccinations with inactivated virus are less effective in the elderly due to the declining competency of the aging immune system. We have explored whether immunological parameters predict poor anti-influenza virus vaccine responses and can be used as biological markers of immunosenescence. One hundred fifty-three residents of community-based retirement facilities aged 65 to 98 years received a trivalent influenza vaccine. Vaccine-induced antibody responses were determined by comparing hemagglutination inhibition titers before and 28 days after immunization. The composition of the T-cell compartment was analyzed by flow cytometry and the sizes of three T-cell subsets, CD4(+) CD45RO(+) cells, CD4(+) CD28(null) cells, and CD8(+) CD28(null) cells, were determined. Only 17% of the vaccine recipients were able to generate an increase in titers of antibody to all three vaccine components, and 46% of the immunized individuals failed to respond to any of the three hemagglutinins. The likelihood of successful vaccination declined with age and was independently correlated with the expansion of a particular T-cell subset, CD8(+) CD28(null) T cells. The sizes of the CD4(+) CD45RO(+) memory T-cell and CD4(+) CD28(null) T-cell subsets had no effect on the ability to mount anti-influenza virus antibody responses. Frequencies of CD8(+) CD28(null) T cells are useful biological markers of compromised immunocompetence, identifying individuals at risk for insufficient antibody responses.

Circadian and seasonal occurrence of subarachnoid and intracerebral hemorrhage

OBJECTIVE

To determine whether the time of onset of subarachnoid hemorrhage (SAH) or intracerebral hemorrhage (ICH) is associated with a time of day or season of year.

BACKGROUND

Prior studies have suggested that there may be a circadian and seasonal pattern of ischemic stroke occurrence, but this is less certain for hemorrhagic stroke. Population-based data have been unavailable.

METHODS

All incident ICH and SAH among residents of Rochester, MN, were ascertained. The medical records of patients were reviewed to determine the time of onset and date of occurrence. The day was divided into 8-hour periods, and the year into seasonal quartiles. Each patient was assigned a period based on the time of onset of symptoms. The data were analyzed by chi(2) analysis to determine whether there was a trend toward increased occurrence based on time period or seasonal quartile of onset.

RESULTS

From 1960 to 1989, there were 155 cases (48 men, 107 women) of incident SAH. From 1975 to 1989, there were 137 cases (57 men, 80 women) of incident ICH. There was a significant increase in the time of onset for ICH and SAH in the 8 AM to 4 PM period (p = 0.005 and p = 0.03, respectively). The concomitant occurrence of hypertension, gender, and age did not affect the time of day of occurrence. In the analysis of seasonal variation, there was a significant increase in events during December, January, and February in the combined SAH and ICH group (p = 0.032) and a trend for SAH alone (p = 0.07) but not for ICH (p = 0.34). Hypertension and age had no impact on the association between season and the occurrence of SAH and ICH.

CONCLUSION

The occurrence of SAH and ICH is increased from 8 AM to 4 PM. The occurrence of hemorrhage is increased during the winter months, but this is likely limited only to SAH.

Bone density in an immigrant population from Southeast Asia

The epidemiology of bone loss in populations of Asian heritage is still poorly known. This study compared the skeletal status of a convenience sample of 396 Southeast Asian immigrants (172 Vietnamese, 171 Cambodians and 53 Laotians) residing in Rochester, Minnesota in 1997 with 684 white subjects previously recruited from an age-stratified random sample of community residents. Areal bone mineral density (BMD, g/cm2) and volumetric bone mineral apparent density (BMAD, g/cm3) were determined for lumbar spine and proximal femur using the Hologic QDR 2000 instrument for the white population and the QDR 4500 for Southeast Asian subjects; the machines were cross-calibrated from data on 20 volunteers. Lumbar spine BMD was 7% higher in white than Southeast Asian women (p < 0.001), and similar results were observed for the femoral neck; lumbar spine BMD was 12% higher in white than nonwhite men (p < 0.001). Race-specific discrepancies were reduced by calculating BMAD: for premenopausal women, lumbar spine and femoral neck differences between whites and Southeast Asians were eliminated; for postmenopausal women the lumbar spine differences persisted (p < 0.0001), while femoral neck BMAD was actually higher for Southeast Asians. There were no race-specific differences in femoral neck BMAD among men of any age (p = 0.312), but lumbar spine BMAD was less for younger (p = 0.042) but not older (p = 0.693) Southeast Asian men. There were differences among the Southeast Asian subgroups, but no clear pattern emerged. Predictors of lumbar spine BMAD in Southeast Asian women were age (p < 0.001), weight (p = 0.015) and gravidity (p = 0.037). Even after adjusting for bone size using BMAD, 32% and 9% of Southeast Asian women and men, respectively, would be considered to have osteoporosis at the femoral neck and 25% and 4%, respectively, at the lumbar spine. These findings indicate a need for culturally sensitive educational interventions for Southeast Asians and for physicians to pursue diagnosis and treatment to prevent osteoporosis-related disabilities in this population.

Fractures following thyroidectomy in women: a population-based cohort study

Hip fracture risk has been associated with hyperthyroidism and thyroidectomy in men and with hyperthyroidism in women, but the influence of thyroidectomy on fracture risk in women has not been adequately addressed. The 630 Rochester, MN women who underwent thyroidectomy in 1950-1974 were followed subsequently for 12,804 person-years (retrospective cohort study) during which 601 fractures were observed. Relative to incidence rates in the community, there was no increase in overall fracture risk (standardized incidence ratio [SIR] 0.9; 95% confidence interval [CI] 0.8-1.00). No increase was seen in limb fractures generally or in distal forearm fractures specifically (SIR 1.1, 95% CI 0.8-1.4). There was a modest but statistically significant increase in the risk of hip fractures following thyroidectomy (SIR 1.3, 95% CI 1.01-1.8), but much greater increases were apparent in the risk of subsequent fractures of the ribs, spine, and pelvis. There was almost a threefold increase in vertebral fractures (SIR 2.8, 95% CI 2.3-3.3), but the excess was mostly observed long after the original operation and may be attributable to ascertainment bias. Fracture risk was associated with advancing age and with the presence of one or more of the diseases that have been associated with secondary osteoporosis but not with a history of hyperthyroidism, extent of thyroid surgery, or subsequent use of thyroid replacement therapy. Thus, with the exception of some fractures of the axial skeleton, which might have been more completely diagnosed among affected women, there was no increase in fracture risk among women following thyroidectomy performed mainly for adenoma or goiter.

Endometrial cancer in Olmsted County, MN: trends in incidence, risk factors and survival

PURPOSE

We updated an earlier study in this community from 1945-1974 in order to assess trends in the incidence of, risk factors for, and survival from endometrial cancer in 1975-1991.

METHODS

Incidence rates were based on all new cases of endometrial cancer diagnosed among Olmsted County, Minnesota, women during the years 1975-1991, with the population denominator from decennial census data. Risk factors were assessed with conditional logistic regression comparing the incidence cases to age- and gender-matched controls with intact uteri seen the same year the case was diagnosed. Survival was assessed using the Kaplan-Meier method.

RESULTS

The incidence of endometrial cancer (age-adjusted to 1970 United States total) in 1975-1991 was 14.3 per 100,000 person-years, which is slightly increased from 1965-74. The rate was 21.7 per 100,000 person-years after adjustment for hysterectomy prevalence. As in the previous study, conjugated estrogen use for six months or more (odds ratio [OR] 2.71; 95% confidence interval [CI] 1.14-6.46) and body mass index (OR 1.06; 95% CI 1.01-1.11) increased the risk of endometrial cancer. The five-year relative survival rate (82%) was not improved over the earlier study.

CONCLUSIONS

A small increase in endometrial cancer incidence was linked to the same risk factors identified in an earlier study in this community. No improvement in survival was seen.

Relative influence of physical activity, muscle mass and strength on bone density

In a population-based sample of 348 men (age 22-90 years) and 351 women (age 21-93 years), we evaluated the relationship of bone density assessed at a variety of skeletal sites by dual-energy X-ray absorptiometry (DXA) with various muscle mass estimates obtained also from the DXA scan and with physical activity by interview and strength assessed both subjectively and objectively. All these parameters declined with age as judged from these cross-sectional data. All estimates of total skeletal muscle mass were strongly correlated with bone density at different skeletal sites. Muscle mass, in turn, was correlated with physical activity and hand strength. In multivariate models including these variables, muscle mass was the strongest determinant of bone density, accounting for 6-53% (mean 27%) of the variance at the different skeletal sites. Physical activity (and/or a physical activity x age interaction) was an independent predictor of bone mass in 48% of the site-specific models and accounted for 0.03-39% (mean 10%) of the variance, while hand strength (and/or a hand strength x age interaction) accounted for up to 4% (mean 1%) of the variance as an independent predictor of bone density in a third of the models. Although these variables together accounted for a large proportion of the variance in bone density, other potential predictors were not assessed in these analyses. The dramatic decline in physical activity over life seemed unable to completely explain the age-related loss of bone mass, and additional research is needed to determine whether the relationship of muscle mass with bone density is a direct one or due instead to other factors such as circulating hormone levels.

A comparison of two comorbidity instruments in arthritis

Comorbidity (CM) is a powerful predictor of health outcome and cost, as well as an important confounder in many epidemiologic studies. However, choosing the most appropriate CM measurement instrument is difficult because comparative data on how the available instruments perform in various disease settings are limited. We collected CM data (from the complete medical records) for two population-based prevalence cohorts with rheumatoid arthritis (RA) and osteoarthritis (OA) and a comparison cohort without arthritis (NA), using two different CM instruments: the Charlson CM index (Charl), which is based on 17 diagnoses each weighted by mortality risk, and the Index of Coexistent Diseases (ICED), which estimates the severity and frequency of 14 comorbid conditions and provides an assessment of the impairment or disability caused by each. Cox proportional hazards modeling was used to assess the impact of the two types of comorbidity scores (Charl and ICED) on survival after prevalence (index) date, adjusting for the age, sex, and disease status. There were 450, 441, and 889 individuals in the RA, OA, and NA groups, respectively, with a mean follow-up period of 10.6 years. During the follow-up, 293, 307, and 546 deaths occurred in the RA, OA, and NA groups, respectively. The mean age and percent females were: 63.3 years, 74%; 70.7 years, 74%; and 67.5 years, 75% for the RA, OA, and NA groups, respectively. Comorbidity was highest in RA, intermediate in OA, and lowest in NA by both Charl and ICED. Cox proportional hazards modeling demonstrated that both Charl and ICED were highly statistically significant predictors of mortality (P<0.0001) after adjusting for age, sex, and disease state (RA, OA, or NA) and that ICED remained highly significant as a predictor of mortality, even after adjusting for Charl. We conclude that estimating CM from medical records using ICED, an instrument that incorporates an assessment of impairment and disability, is feasible and that such as assessment provides information that independently predicts mortality, even after adjusting for the results of traditional diagnosis-based CM measures, such as Charl.

The ups and downs of anorexia nervosa

OBJECTIVE

We updated our incidence study by identifying Rochester, Minnesota, residents diagnosed with anorexia nervosa during 1985 through 1989.

METHOD

From a community-based epidemiologic resource, 2,806 medical records with diagnoses including anorexia nervosa, eating disorder, bulimia, amenorrhea and other conditions were screened to identify new cases of anorexia nervosa.

RESULTS

Two hundred eight (193 females and 15 males) residents fulfilled standard diagnostic criteria for anorexia nervosa. The overall age-sex-adjusted incidence rate was 8.3 per 100,000 person-years. The age-adjusted incidence among females was 15.0 per 100,000 person-years compared to 1.5 per 100,000 among males. The long-term linear increase for 15 to 24-year-old females noted during the first 50 years of the study continued. The disorder remained less frequent among older females.

DISCUSSION

Anorexia nervosa remains a relatively common disorder among young females. While there are short-term fluctuations in incidence, the long-term increasing trend for 15 to 24-year-old females has continued.

Mortality in rheumatoid arthritis: have we made an impact in 4 decades?

OBJECTIVE

To evaluate trends in survival among patients with rheumatoid arthritis (RA) over the past 4 decades.

METHODS

Three population based prevalence cohorts of all Rochester, Minnesota, residents age > or =35 years with RA (1987 American College of Rheumatology criteria) on January 1, 1965, January 1, 1975, and January 1, 1985; and an incidence cohort of all new cases of RA occurring in the same population between January 1, 1955 and January 1, 1985, were followed longitudinally through their entire medical records (including all inpatient and outpatient care by any provider) until death or migration from the county. Mortality was described using the Kaplan-Meier method and the influence of age, sex, rheumatoid factor (RF) positivity, and comorbidity (using the Charlson Comorbidity Index) on mortality was analyzed using Cox proportional hazards models.

RESULTS

Mortality was statistically significantly worse than expected for each of the cohorts (overall p<0.0001). A trend toward increased mortality in the 1975 and 1985 prevalence cohorts compared to the 1965 prevalence cohort was present, even after adjusting for significant predictors of mortality (age, RF positivity, and comorbidity). Survival for the general population of Rochester residents of similar age and sex improved in 1975 compared to 1965, and in 1985 compared to 1975.

CONCLUSION

The excess mortality associated with RA has not changed in 4 decades. Moreover, people with RA have not enjoyed the same improvements in survival experienced by their non-RA peers. More attention should be paid to mortality as an outcome measure in RA.

Comorbidity in arthritis

OBJECTIVE

To describe the relative frequency of selected comorbidities in 2 population based prevalence cohorts of patients with rheumatoid arthritis (RA) and osteoarthritis (OA) compared to age and sex matched community controls.

METHODS

Using the population based data resources of the Rochester Epidemiology Project, we assembled 3 prevalence cohorts of all residents of Olmsted County, Minnesota, with RA (1987 American College of Rheumatology criteria) and age and sex matched controls without arthritis on January 1, 1965, January 1, 1975, and January 1, 1985. Cases and controls were followed longitudinally through their complete (inpatient and outpatient) medical records beginning 10 years prior to the prevalence (or index) date until death, migration from the county, or January 1, 1995. Comorbidity was assessed yearly using the Charlson Comorbidity Index and the Index of Co-existent Diseases (ICED). Descriptive statistics were used to illustrate the baseline characteristics of the study population and the frequency of individual comorbidities in each of the 3 groups over the followup period. Cox proportional hazards modeling was used to assess the risk for each individual comorbidity among patients with arthritis compared to controls and to identify significant predictors of an increase in comorbidity level over time.

RESULTS

Our study population included 450 RA, 441 OA, and 891 control subjects. The age and sex distributions of cases and their controls were similar. Over the followup period, patients with RA had a higher likelihood of developing congestive heart failure, chronic pulmonary disease, dementia, and peptic ulcer disease, while cases with OA had a significantly higher risk of developing peptic ulcer disease and renal disease. Among patients with either RA or OA, age, male sex, and baseline comorbidity were significant predictors of a rise in comorbidity. The presence of RA was a highly significant predictor of a rise in comorbidity from one year to the next, even after controlling for the effects of age, sex, and baseline comorbidity (p = 0.0004 for the Charlson and p = 0.006 for the ICED).

CONCLUSION

These data indicate that the burden of illness among people with arthritis is higher than for nonarthritics and that this burden appears to be increasing over time, particularly in RA. These results suggest that specialized chronic disease care will be increasingly important for the future health care needs of people with RA.

Long-term fracture risk among women with anorexia nervosa: a population-based cohort study

OBJECTIVE

To determine if fractures represent an important problem for women with anorexia nervosa who may fail to achieve peak bone mass and may experience premature bone loss from decreased estrogen levels.

PATIENTS AND METHODS

In this population-based retrospective cohort study, we identified 208 Rochester, Minn, residents that were first diagnosed as having anorexia nervosa between 1935 and 1989, whose subsequent fractures were documented in contemporary medical records and compared with expected numbers of fractures (standardized incidence ratios [SIRs]).

RESULTS

Subjects were followed up for 2689 person-years during which time 45 patients suffered 88 fractures. Fracture risk was increased among the 193 women (SIR, 2.9; 95% confidence interval, 2.0-3.9) as well as the 15 men (SIR, 3.4; 95% confidence interval, 1.1-7.9). The cumulative incidence of any fracture at 40 years after the diagnosis of anorexia nervosa was 57%. Fractures of the hip, spine, and forearm were late complications, occurring on average 38, 25, and 24 years, respectively, after diagnosis.

CONCLUSION

Young women with anorexia nervosa are at increased risk of fractures later in life. Greater attention should be paid to the skeletal health of these individuals.

Primary hyperparathyroidism and the risk of fracture: a population-based study

While severe primary hyperparathyroidism (HPT) is clearly associated with osteitis fibrosa cystica, it remains uncertain whether mild, asymptomatic primary HPT adversely affects the skeleton. Thus, we assessed the incidence of age-related fractures in a large, population-based inception cohort of 407 cases of primary HPT (93 men and 314 women) recognized during the 28-year period, 1965-1992. Fracture risk was assessed by comparing new fractures at each site to the number expected from gender- and age-specific fracture incidence rates for the general population (standardized incidence ratios, SIRs). These community patients with primary HPT mostly had mild disease (mean +/- SD serum calcium, 10.9 +/- 0.6 mg/dl). Altogether, 471 fractures occurred during 5766 person-years of follow-up. Overall fracture risk was significantly increased in these patients (SIR 1.3, 95% confidence interval [CI] 1.1-1.5). Primary HPT was associated with an increased risk of vertebral (SIR 3.2, 95% CI 2.5-4.0), distal forearm (SIR 2.2, 95% CI 1.6-2.9), rib (SIR 2.7, 95% CI 2.1-3.5), and pelvic fractures (SIR 2.1, 95% CI 1. 1-3.5). The risk of proximal femur fractures was only marginally increased (SIR 1.4, 95% CI 1.0-2.0). By univariate analysis, increasing age and female gender were significant predictors of fracture risk, although higher serum calcium levels were also associated with increased fracture risk, and parathyroid surgery may have had a protective effect. By multivariate analysis, however, only age (relative hazard [RH] per 10-year increase, 1.6, 95% CI 1. 4-1.9) and female gender (RH 2.3, 95% CI 1.2-4.1) remained significant independent predictors of fracture risk. Thus, primary HPT among unselected patients in the community is associated with a significant increase in the risk of vertebral, Colles', rib, and pelvic fractures. These data have important implications for the current trend to recommend nonsurgical management for patients with mild primary HPT.

Fracture risk after surgery for peptic ulcer disease: a population-based cohort study

In the 30-year period from 1956 to 1985, 471 Rochester, MN residents had an initial operation for peptic ulcer disease, 438 of whom were followed for at least 30 days (median 14.8 years per subject). In this population-based cohort, risk was elevated for all of the fracture sites traditionally associated with osteoporosis, including the proximal femur (standardized incidence ratio [SIR] 2.5, 95% CI 1.9-3.3), vertebra (SIR 4.7, 95% CI 3.8-5.7), and distal forearm (SIR 2.2, 95% CI 1.5-3.1). Fracture risk rose with age and was greater among women than men, but there was no influence on overall fracture risk of ulcer type or nature of the operation. In multivariate analyses, the independent predictors of vertebral fractures were age (hazard ratio [HR] per 10-year increase 1.8, 95% CI 1.6-2.0), use of corticosteroids (HR 2.3, 95% CI 1.01-5.2), thyroid replacement (HR 2.5, 95% CI 1.4-4.6), chronic anticoagulation (HR 2.3, 95% CI 1.1-4.6), and the presence of one or more conditions associated with secondary osteoporosis (HR 1.6, 95% CI 1.2-2.1). Gastrectomy with Billroth II reconstruction appeared to be relatively protective (HR 0.5, 95% CI 0.3-0.9), but such patients still had an increased risk of vertebral fractures compared with community residents generally (SIR 3.6, 95% CI 2.4-5.4). The independent predictors of hip fracture risk in this cohort were age (HR 2.7, 95% CI 2.1-3.5) and use of corticosteroids (HR 5.8, 95% CI 2.2-15.3) or anticonvulsants (HR 4.6, 95% CI 1.8-12.0), while higher body mass index was protective (HR 0.9, 95% CI 0.8-0.96). The independent predictors of distal forearm fractures were female gender (HR 4.7, 95% CI 2.2-10.1) and chronic anticoagulant use (HR 2.8, 95% CI 1.1-7.3). Thus, while the risk of osteoporotic fractures was significantly increased among patients operated for peptic ulcers, this appeared to be due more to specific characteristics of the cohort than to adverse effects of particular surgical procedures.

Modeling the lifetime costs of rheumatoid arthritis

OBJECTIVE

To develop an analytical approach for estimating the lifetime costs of rheumatoid arthritis (RA) using existing population based cross sectional data, and to use this estimate to describe the potential cost-effectiveness of bone marrow transplantation for RA.

METHODS

Estimates of arthritis related costs (direct, indirect, and nonmedical) and mortality were obtained from previously assembled population based cohorts. A mathematical model was designed defining 25 hypothetical ratios (RA/NA) representing the proportionate excess cost of RA each year for the 25 years following a diagnosis of RA. Using age and sex-specific cost estimates, we then simulated a vector of 25 ratios 1000 times. Each age and sex-specific randomly generated variable was converted to an estimated dollar amount (in 1995 dollars US) of excess cost attributable to RA. All dollar amounts were discounted by 3% per year. Finally, each vector of 25 discounted dollar amounts was summed to yield an estimate of the total excess medical costs in 1995 dollars for the first 25 years of a person's lifetime following a diagnosis of RA. Because not every one of these hypothetical individuals would be expected to live all 25 years, we used the standardized mortality ratio for an individual with RA (from our inception cohort) and multiplied it by the age-specific 1990 mortality rates for Minnesota whites to estimate how many of the 1000 randomly generated hypothetical individuals could be expected to die during each of the 25 years. For these, the summation of estimated cost was truncated at the death year. This process yielded, for each age and sex, a sample of 1000 sums of 25 (or fewer) excess costs all in terms of 1995 dollars that correspond to the excess cost during the first 25 years after an RA diagnosis, adjusted for differential survival among patients with RA compared to nonarthritic controls. The distribution of these sums thus represented a distribution of the 1995 dollars that could be saved if RA could be "cured" soon after incidence.

RESULTS

Our simulation analyses indicated that the median lifetime incremental costs of RA range roughly from ,$61,000 to $ 122,000. Incremental costs were higher for younger individuals compared to older individuals and were consistent over all percentiles and age groups. No systematic relationship between the incremental costs of females with RA compared to males was identified.

CONCLUSION

These data suggest that interventions such as autologous bone marrow transplantation, which has recently been estimated to cost roughly $60,000, may be cost saving if they eliminate the downstream incremental costs of RA.

The epidemiology of rheumatoid arthritis in Rochester, Minnesota, 1955-1985

OBJECTIVE

To describe trends in the epidemiology of rheumatoid arthritis (RA) over a period of 30 years in a population-based cohort.

METHODS

An inception cohort of Rochester, Minnesota residents who were > or =35 years of age and had RA (as defined by the 1987 American College of Rheumatology criteria for RA) first diagnosed between January 1, 1955 and January 1, 1985 was assembled and followed up until January 1, 1995. Incidence rates were age- and sex-adjusted to the 1970 US white population. Prevalence of RA in this cohort was estimated on January 1, 1985. A birth-cohort analysis was performed by calculating and comparing incidence rates in each of 16 birth cohorts.

RESULTS

Of the 425 Rochester residents who fulfilled the inclusion criteria, there were 113 men (26.6%) and 312 women (73.4%), with a mean age at diagnosis of 60.2 years. The mean followup time was 15.1 years. The overall age- and sex-adjusted annual incidence of RA among Rochester, Minnesota residents > or =35 years of age (1955-1985) was 75.3 per 100,000 population (95% confidence interval 68.0-82.5). This incidence was approximately double in women compared with that in men and increased steadily with age, until age 85, after which the incidence of RA decreased. Secular trends in the incidence of RA over the entire study period were demonstrated. The overall prevalence of RA on January 1, 1985 was approximately 1%. The birth-cohort analysis showed peak incidence rates in the 1880-1895 birth cohorts.

CONCLUSION

The epidemiology of RA is dynamic. The findings in this study lend further support to the hypothesis of a host-environment interaction in the pathogenesis of RA.

Forearm fractures as predictors of subsequent osteoporotic fractures

To assess the ability of distal forearm fractures to predict future fractures, we conducted a population-based retrospective cohort study among the 1288 residents (243 men, 1045 women) of Rochester, Minnesota age 35 years or older who experienced their first distal forearm fracture in 1975-94. During 9664 person-years of follow-up, 548 patients experienced 1109 subsequent fractures, excluding 195 that occurred on the same day as the index forearm fracture. The cumulative incidence of any subsequent fracture was 55% by 10 years and 80% by 20 years following the initial distal forearm fracture. Compared to expected fracture rates in the community, the risk of a hip fracture following the index forearm fracture was increased 1.4-fold in women (95% CI, 1.1-1.8) and 2.7-fold in men (95% CI, 0.98-5.8). In women, the risk of hip fracture differed by age, as we had found in a previous study. Women over age 70 had a 1.6-fold increase (95% CI, 1.2-2.0) in subsequent hip fracture risk whereas women who sustained their first forearm fracture before age 70 years did not have significantly increase risk. By contrast, vertebral fractures were significantly increased at all ages, with a 5.2-fold increase (95% CI, 4.5-5.9) in risk among women and a 10.7-fold increase (95% CI, 6.7-16.3) among men following a first distal forearm fracture. The increased risk in men suggests that a sentinel forearm fracture should not be ignored. Among the women, we also found a missed opportunity for intervention as hormone replacement therapy was underutilized.

Fracture incidence in Olmsted County, Minnesota: comparison of urban with rural rates and changes in urban rates over time

Using the data resources of the Rochester Epidemiology Project, we carried out a descriptive study of fracture incidence among the residents of Olmsted County, Minnesota. During the 3-year period 1989-91, 2901 County residents > or = 35 years of age experienced 3665 separate fractures. The age- and sex-adjusted (to 1990 United States whites) incidence of any fracture was 2205 per 100,000 person-years (95% CI, 2123 to 2286) and that of all fractures was 2797 per 100,000 (95% CI, 2705 to 2889). Age-adjusted fracture rates were 40% greater among women. Incidence rates increased with age in both sexes. One-third of the fractures involved the hip, spine or distal forearm - the skeletal sites traditionally associated with osteoporosis. The age- and sex-adjusted incidence of fractures due to moderate trauma (2205 per 100,000 person-years; 95% CI, 2106 to 2303) was twice that of fractures due to more severe trauma (1164 per 100,000; 95% CI, 1106 to 1223) and 12 times that of pathological fractures (178 per 100,000; 95% CI, 133 to 222). Overall fracture rates were 15% greater among residents of the central city of Rochester compared with the rural portion of Olmsted County. The incidence of limb fractures among Rochester residents was 14% higher than comparable rates documented for this community 20 years earlier in 1969-71, due mainly to a substantial increase in the incidence of leg fractures.

Fracture risk among patients with urolithiasis: a population-based cohort study

In a population-based retrospective cohort study, 624 Rochester, Minnesota residents with an initial symptomatic episode of urolithiasis in 1950 to 1974 were followed for 11,909 person-years for subsequent age-related fractures. During this period of observation, the number of patients with a first vertebral fracture was over four times the number expected on the basis of vertebral fracture incidence rates in the general population of Rochester [standardized morbidity ratio (SMR), 4.3; 95% confidence interval, 3.4 to 5.3]. The risk of vertebral fracture was elevated among men as well as women, and was associated with increasing age and with the use of corticosteroids for more than six months. However, vertebral fracture risk was increased nearly fourfold (SMR 3.9; 95% confidence interval, 3.0 to 4.9) among the urolithiasis patients without such exposure, which suggests that corticosteroids do not completely account for the association with vertebral fractures. There was no increase in the risk of hip, pelvis, proximal humerus or distal forearm fractures in this cohort of patients, and their survival was not impaired. Additional studies are needed to define the pathophysiology of vertebral fractures among patients with urolithiasis.

Long-term trends in the incidence of distal forearm fractures

In this population-based descriptive study covering the 50-year period, 1945-94, there was a statistically significant increase in distal forearm fractures due to severe trauma in both women and men (p < 0.001) but no secular increase in fractures due to moderate trauma (approximately osteoporosis). Since fractures attributed to severe trauma comprised a greater proportion of the total in men (52%) than women (21%), an overall doubling of age-adjusted forearm fracture incidence in men between 1945 and 1994 was statistically significant (p < 0.001), but the 7% increase in age-adjusted rates among women was not (p = 0.90). While the epidemiological pattern of distal forearm fracture incidence in Rochester was similar to that seen elsewhere, the overall incidence rate of 287.4 per 100,000 person-years (95% CI 267.7-307.1) in 1985-94 was less than current rates in Sweden, presumably because the great increase in distal forearm fracture incidence seen, for example, in Malmö between 1953-57 and 1980-81 was not observed in Rochester. The trends in distal forearm fracture rates in Rochester men and women over the past 50 years are broadly consistent with trends in hip fracture incidence in this community over the same time span.

Direct medical costs unique to people with arthritis

OBJECTIVE

We report the results of a population based analysis of all health services used and charges incurred over a one-year period among a community based cohort of persons with a diagnosis of arthritis [including both osteoarthritis (OA) and rheumatoid arthritis (RA)] compared to a similar cohort of individuals from the same community who have never had a diagnosis of arthritis (NA), to examine the attributable costs of this chronic condition.

METHODS

The unique resources of the Rochester Epidemiology Project were used to assemble the arthritis prevalence cohorts and the population based control cohort. The Olmsted County Health Care Utilization and Expenditures Database was used to collect information on health services utilization and charges.

RESULTS

The average direct medical charges for the RA, OA, and NA cohorts were $3,802.05, $2,654.51, and $1,387.83, respectively (age and sex adjusted, p < 0.0001 for both the RA vs NA and OA vs NA comparisons). The median charges for these 3 groups were $1,050.00, $663.55, and $232.04 for the RA, OA, and NA groups, respectively (age and sex adjusted p < 0.0001 for both the RA vs NA and OA vs NA comparisons). These analyses indicated that, compared to the NA cohort both the OA and the RA prevalence cohorts incurred statistically significantly more charges, not only for the musculoskeletal disease care, but also for the care of numerous other conditions including respiratory, cardiovascular, gastrointestinal, neurological, and psychiatric conditions; and for general medical care. Individuals with arthritis (both OA and RA) also incurred statistically significantly more charges for diagnostic and therapeutic procedures, in-hospital care, imaging studies, physician services, equipment, and laboratory studies. Use of prescription medications was statistically significantly more common in the RA and OA groups compared to NA (96.3, 96, and 83%, respectively; age and sex adjusted p = 0.006 for the OA vs NA comparison and p = 0.015 for RA vs NA).

CONCLUSION

These results emphasize the importance of considering all health services utilization (rather than only disease specific use) when estimating the economic effect of a chronic illness such as arthritis.

Indirect and nonmedical costs among people with rheumatoid arthritis and osteoarthritis compared with nonarthritic controls

OBJECTIVE

Compared to rheumatoid arthritis (RA), osteoarthritis (OA) is considered much more benign and much less costly. We sought to describe the economic effects of RA and OA, in terms of the indirect and nonmedical expenditures, compared to nonarthritic controls.

METHODS

Using our unique population based data resources, we developed a model for estimating and comparing disease specific costs among 2 randomly selected, community based samples of 200 patients each with RA and OA and a control group of 200 individuals from the same community who do not have arthritis. Data were collected using a pretested postal survey. Age and sex adjusted comparisons were conducted across the 3 groups, and predictors of cost and utilization were identified using logistic regression modeling.

RESULTS

There were 123, 116, and 94 respondents among the RA, OA, and nonarthritis groups, respectively. The average age and the female-to-male ratios were higher in the OA and RA groups compared to the nonarthritis group. Patients with RA and OA required 3 times more days of care for their conditions compared to nonarthritics (p < 0.0001) and incurred significantly more expenditures for home or child care (p = 0.01) and other services (p = 0.001) (i.e., medical equipment, assistive devices, or home remodeling) compared to nonarthritics. In addition, patients with RA were significantly more likely to have lost their job or to have retired early due to their illness (p = 0.001); were the most likely to have reduced their work hours or stopped working entirely due to their illness (p = 0.003); and were 3 times more likely to have had a reduction in household family income than either individuals with OA or those without arthritis (p = 0.0001). Fifteen percent of respondents with RA were unable to get a job because of their illness, while 3% of respondents with OA and only 1% of nonarthritic respondents reported this experience (p = 0.001). Logistic regression analysis revealed that functional status and pain score, as well as the presence of either RA or OA, were significant predictors of cost and health services utilization.

CONCLUSION

Disease specific indirect and nonmedical costs for OA are substantial and approach those for RA. This has important societal implications, given the high prevalence of OA.

Fracture risk following bilateral oophorectomy

To assess fracture risk following bilateral oophorectomy, we conducted a population-based retrospective cohort study among the 463 Rochester, Minnesota women who underwent bilateral oophorectomy for benign ovarian conditions in 1950-1979. During 7220 person-years of observation, there appeared to be a modest increase in the risk of distal forearm fractures (standardized morbidity ratio [SMR] 1.4; 95% CI 1.0-2.0) and vertebral fractures (SMR 1.9; 95% CI 1.3-2.8) but not hip fractures (SMR] 1.1; 95% CI 0.6-1.9). Although our statistical power was quite limited, there was a suggestion that women who became estrogen deficient at a young age were at greater risk of fracture. However, the youngest women were more likely to be on estrogen replacement therapy, and for longer durations, so that the average age at the onset of estrogen deficiency in this population was 47 years.

A mathematical model that improves the validity of osteoarthritis diagnoses obtained from a computerized diagnostic database

We developed an algorithm, using recursive partitioning, that utilized information from a computerized, diagnostic database to predict the diagnosis of osteoarthritis as determined by medical record review. The complete (inpatient and outpatient) medical records for a random sample of 400 Olmsted County, Minnesota residents with a database diagnosis consistent with osteoarthritis were reviewed, and confirmation or rejection of the diagnosis was accomplished. Of the 387 patients in our sample, only 232 (a positive predictive value of 60%) fulfilled diagnostic criteria for osteoarthritis following medical record review. A classification tree was created that used information from the diagnostic database to partition the study population according to the proportion of individuals with a "true" diagnosis of osteoarthritis (based on medical record review). The receiver-operating characteristic curve generated from these data illustrated that the algorithm substantially improved the validity of the database diagnosis, yielding a positive predictive value of 89% and a negative predictive value of 70% (sensitivity of 75% and specificity of 86%) at a selected cutoff point. This model also provides the capability of selecting the cutoff point to favor either specificity or sensitivity. These data demonstrate that a mathematical model can substantially improve the validity of computerized diagnostic databases in osteoarthritis.

Costs of osteoarthritis: estimates from a geographically defined population

Using the population based data resources of the Rochester Epidemiology Project and a postal survey, we estimated all costs (direct medical, indirect medical, and nonmedical) incurred among a population based prevalence cohort of individuals with osteoarthritis (OA) and a nonarthritic comparison cohort. Cost estimates were compared between the 2 groups adjusting for age and sex differences. Our results demonstrated that people with OA incur substantial incremental medical costs, not only for arthritis care, but also for the care of neurological, gastrointestinal, cardiac, and respiratory conditions compared to nonarthritics. These data also demonstrated important and statistically significantly higher levels of work disability among people with OA compared to their age and sex adjusted peers without arthritis from the same community.

Competitive athletes: preinjury and postinjury mood state and self-esteem

In a prospective study, we determined whether preinjury and postinjury differences existed in the mood state and self-esteem of competitive athletes. The influence of severity of injury, gender, level of participation in sports, and type of sport on these dependent variables was also measured. Among 238 male and 38 female athletes from hockey, basketball, baseball, and volleyball teams, 36 sustained 43 injuries. Significant postinjury increases were noted for depression (P < 0.0001) and anger (P = 0.0012), whereas vigor (P < 0.0001) was significantly less after injury. When the 36 injuries were classified, 27 were minor or moderate (nonparticipation in sports for only one or two weekly assessments), and 9 were severe (nonparticipation for three or more weekly assessments). When a stepwise multiple regression equation was used to predict the scores for postinjury depression, the only significant predictor was the severity of injury (F = 8.48 [1, 34]; R2 = 0.30; P = 0.0063). Of the following physical and psychosocial variables--level of participation, type of sport, age, previous injury, preinjury stress, gender, mood state scales, and self-esteem--only level of participation (P < 0.0001) and type of sport (P = 0.0004) were predictors of injury. The significant preinjury and postinjury differences in mood state suggest that postinjury mood disturbances reported in previous studies are likely attributable to the occurrence of injury, are related to the severity of injury, and do not merely reflect a disturbed preinjury mood.

Second natural history study of congenital heart defects. Materials and methods

Results of the location and recruitment efforts and comparisons of responses from patients who cooperated at different levels in the Second Natural History Study of Congenital Heart Defects are included because they influenced the choice of analytic methods and are essential to the generalizability of the results to the entire study cohort. Included are examination and data collection protocols (e.g., protocol definitions, test procedures, and data editing), statistical methods (e.g., box plots, survival curves, multivariable models, and rate adjustment), participation results (e.g., proportional odds analysis, mortality, location, recruitment, and full participants, including comparison of questionnaire responses and comparison of questionnaire response and physician history), and a discussion.

Causes of death in patients with tuberous sclerosis

Of the 355 patients with tuberous sclerosis complex (TSC) examined at the Mayo Clinic, 49 had died (9 of causes other than TSC). We attempted to determine what pattern of organ involvement occurred most often in the 40 patients who died of TSC. One baby died of cardiac failure due to cardiac rhabdomyomas, and one child died of rupture of an aneurysm of the thoracic aorta. Eleven patients died of renal disease, which was the commonest cause of death. Ten patients died as a result of brain tumors, and four patients (who were 40 years of age or older) died of lymphangiomyomatosis of the lung. Thirteen patients with severe mental handicaps died of either status epilepticus or bronchopneumonia; in all but one of these patients, the only source of information was the death certificate. Survival curves show a decreased survival for patients with TSC in comparison with that for the general population. Patients with TSC need lifelong follow-up for early detection of potentially life-threatening complications.