Proportion and associated factors of meeting the 2018 Physical Activity Guidelines for Americans in adults with or at risk for knee osteoarthritis.

OBJECTIVES: Evaluate the prevalence of meeting the updated 2018 Physical Activity Guidelines for Americans (150 unbouted minutes in moderate-to-vigorous intensity physical activity [MVPA]) and determine cross-sectional factors associated with Guideline attainment in a community-based cohort of adults with or at elevated risk for knee osteoarthritis (OA). METHODS: Physical activity was monitored for 1 week in a subset of Osteoarthritis Initiative (OAI) participants with or at increased risk for knee OA. Accelerometer-measured weekly MVPA minutes were calculated; sociodemographic (age, sex, race, education, and working status) and health-related (body mass index [BMI], comorbidity, depressive symptoms, radiographic knee OA, and frequent knee symptoms) factors were assessed. We evaluated the prevalence of meeting 2018 Guidelines and used multivariate partial proportional odds model to identify factors associated with Guideline attainment, controlling for other factors in the model. RESULTS: Among 1922 participants (age 65.1 [standard deviation 9.1] years, BMI 28.4 [4.8] kg/m2, 55.2% women), 44.1% men and 22.2% women met the 2018 PA Guidelines. Adjusted cross-sectional factors associated with not-meeting 2018 Guidelines were: women, older age, higher BMI, non-Whites, depressive symptoms, not working, and frequent knee symptoms. CONCLUSION: In community-recruited adults with or at high risk for knee OA, more than 50% of men and nearly 80% of women failed to achieve the 2018 recommended level of at least 150 weekly unbouted minutes of MVPA. Study findings support gender and racial disparity in Guideline attainment and suggest addressing potentially modifiable factors (e.g., BMI, depressive symptoms, and frequent knee symptoms) to optimize benefits in PA-promoting interventions.

Reallocating time spent in sleep, sedentary behavior and physical activity and its association with pain: a pilot sleep study from the Osteoarthritis Initiative.

OBJECTIVE: Being physically active has broad health benefits for people with osteoarthritis (OA), including pain relief. Increasing physical activity (PA) requires reducing time in other behaviors within a fixed 24-h day. We examined the potential benefits in relation to pain from trading time in one type of wake or sleep behavior for another. METHOD: In this cross-sectional study, we used isotemporal logistic regression models to examine the estimated effect on pain from replacing time in one behavior with equal time in another, controlling for sociodemographic and health factors. Stratified analysis was conducted by the report of restless sleep. Sleep and wake behaviors [sedentary behavior (SB), light PA, moderate PA] were monitored by accelerometer in a pilot study of 185 Osteoarthritis Initiative (OAI) participants. Outcomes were bodily pain interference and knee pain. RESULTS: Moderate PA substituted for an equivalent time in sleep or other types of wake behaviors was most strongly associated with lower odds of pain (bodily pain interference odds reduced 21-25%, knee pain odds reduced 17-20% per 10-min exchange). These beneficial associations were particularly pronounced in individuals without restless sleep, but not in those with restless sleep, especially for bodily pain interference. CONCLUSION: Interventions promoting moderate physical activities may be most beneficial to address pain among people with or at high risk for knee OA. In addition to encouraging moderate-intensity PA, pain management strategies may also include the identification and treatment of sleep problems.

Associations of osteoprotegerin with coronary artery calcification among women with systemic lupus erythematosus and healthy controls.

Objective We tested the hypothesis that higher circulating levels of osteoprotegerin (OPG) are related to higher levels of coronary artery calcification (CAC) among women with systemic lupus erythematosus (SLE) compared with healthy controls (HCs). Methods Among 611 women in two age- and race-matched SLE case-control studies, OPG was assayed in stored blood samples (HEARTS: plasma, n cases/controls = 122/124, and SOLVABLE: serum, n cases/controls = 185/180) and CAC was measured by electron beam computed tomography. Results In both studies, SLE patients had higher OPG and CAC levels than HCs. Higher OPG was associated with high CAC (>100 vs.100) among SLE, and with any CAC (>0 vs. 0) among HCs. Multivariable-adjusted OR (95% CI) for OPG tertile 3 vs. 1 was 3.58 (1.19, 10.76), p trend = 0.01 for SLE, and 2.28 (1.06, 4.89), p trend = 0.04 for HCs. Associations were attenuated when age-adjusted, but remained significant for HC women aged ≥ 40 and SLE women aged ≥ 50. ROC analyses identified 4.60 pmol/l as the optimal OPG cutpoint for predicting high CAC (>100) among SLE patients with sensitivity = 0.74 and specificity = 0.61, overall, but 0.92 and 0.52, respectively, for SLE patients aged ≥ 50. Conclusion Our cross-sectional results suggest that higher OPG levels are related to higher CAC levels among women with SLE vs. healthy controls.

Fatigue, patient reported outcomes, and objective measurement of physical activity in systemic lupus erythematosus.

OBJECTIVE: Fatigue is a common symptom in systemic lupus erythematosus (SLE), and engaging in physical activity may reduce fatigue. We aimed to characterize relationships between fatigue, other health status measures assessed with the Patient Reported Outcomes Measurement Information System (PROMIS) instruments, and accelerometer-based physical activity measurements in patients with SLE. The internal consistency of each PROMIS measure in our SLE sample was also evaluated. METHODS: This cross-sectional study analyzed 123 adults with SLE. The primary fatigue outcome was Fatigue Severity Scale score. Secondary outcomes were PROMIS standardized T-scores in seven health status domains. Accelerometers were worn for seven days, and mean daily minutes of light, moderate/vigorous, and bouted (10 minutes) moderate/vigorous physical activity were estimated. Cronbach's alpha was determined for each PROMIS measure to assess internal consistency. Relationships between Fatigue Severity Scale, PROMIS, and physical activity were summarized with Spearman partial correlation coefficients (r), adjusted for average daily accelerometer wear time. RESULTS: Mean Fatigue Severity Scale score (4.3, SD 1.6) was consistent with clinically relevant levels of fatigue. Greater daily and bouted moderate/vigorous physical activity minutes correlated with lower Mean Fatigue Severity Scale score (r = -0.20, p = 0.03 and r = -0.30, p = 0.0007, respectively). For PROMIS, bouted moderate/vigorous physical activity minutes correlated with less fatigue (r = -0.20, p = 0.03). PROMIS internal consistency was excellent, with Cronbach's alpha > 0.90 for each domain. Mean PROMIS T-scores for fatigue, pain interference, anxiety, sleep disturbance, sleep-related impairment, and physical function were worse than reported for the general US population. More moderate/vigorous physical activity minutes were associated with less pain interference (r = -0.22, p = 0.01). Both light physical activity and moderate/vigorous physical activity minutes correlated with better physical function (r = 0.19, p = 0.04 and r = 0.25, p = 0.006, respectively). CONCLUSION: More time spent in moderate/vigorous physical activity was associated with less fatigue (Fatigue Severity Scale and PROMIS), less pain interference, and better physical function (PROMIS). PROMIS had excellent internal consistency in our SLE sample, and six of seven PROMIS measures indicated poorer average health status in SLE patients compared with the general US population.

Association of Physical Activity Measured by Accelerometer, Knee Joint Abnormalities, and Cartilage T2 Measurements Obtained From 3T Magnetic Resonance Imaging: Data From the Osteoarthritis Initiative.

OBJECTIVE: To study the cross-sectional association between physical activity measured with an accelerometer, structural knee abnormalities, and cartilage T2 values assessed with 3T magnetic resonance imaging (MRI). METHODS: We included 274 subjects from the Osteoarthritis Initiative cohort without definite radiographic osteoarthritis (Kellgren/Lawrence grades 0 and 1) and with at most mild pain, stiffness, and functional limitation in the study knee (Western Ontario and McMaster Universities Osteoarthritis Index scale 0-1), which had not limited their activity due to knee pain. Physical activity was measured over 7 days with an ActiGraph GT1M accelerometer. Subjects were categorized by quartile of physical activity based on the average daily minutes of moderate to vigorous physical activity (mv-PA). MRI images of the right knee (at 48-month visit) were assessed for structural abnormalities using a modified Whole-Organ Magnetic Resonance Imaging Score (WORMS) and for T2 relaxation times derived from segmented cartilage of 4 femorotibial regions and the patella. WORMS grades and T2 measurements were compared between activity quartiles using a linear regression model. Covariates included age, sex, body mass index, knee injury, family history of knee replacement, knee symptoms, hip and ankle pain, and daily wear time of the accelerometer. RESULTS: Higher mv-PA was associated with increased severity (P = 0.0087) and number of lesions of the medial meniscus (P = 0.0089) and with severity of bone marrow edema lesions (P = 0.0053). No association between cartilage lesions and mv-PA was found. T2 values of cartilage (loss, damage, and abnormalities) tended to be greater in the higher quartiles of mv-PA, but the differences were nonsignificant. CONCLUSION: In knees without radiographic osteoarthritis in subjects with no or mild knee pain, higher physical activity levels were associated with increases in meniscal and bone marrow edema pattern lesions.

Sedentary behavior and blood pressure control among osteoarthritis initiative participants.

OBJECTIVE: To examine the association between sedentary behavior and blood pressure (BP) among Osteoarthritis Initiative (OAI) participants. DESIGN: We conducted a cross-sectional analysis of the OAI 48-month visit participants whose physical activity was measured using accelerometers. Participants were classified into four quartiles according to the percentage of wear time that was sedentary (<100 activity counts per min). Users of antihypertensive medications or non-steroidal anti-inflammatory drugs (NSAIDs) were excluded. Our main outcomes were systolic and diastolic blood pressures (SBP and DBP) and "elevated BP" defined as BP ≥ 130/85 mm Hg. RESULTS: For this study cohort (N = 707), mean BP was 121.4 ± 15.6/74.7 ± 9.5 mm Hg and 33% had elevated BP. SBP had a graded association with increased sedentary time (P for trend = 0.02). The most sedentary quartile had 4.26 mm Hg higher SBP (95% confidence interval (CI), 0.69-7.82; P = 0.02) than the least sedentary quartile, adjusting for age, moderate-to-vigorous (MV) physical activity, and other demographic and health factors. The probability of having elevated BP significantly increased in higher sedentary quartiles (P for trend = 0.046). There were no significant findings for DBP. CONCLUSION: A strong graded association was demonstrated between sedentary behavior and increased SBP and elevated BP, independent of time spent in MV physical activity. Reducing daily sedentary time may lead to improvement in BP and reduction in cardiovascular risk.

The relationship between specific tissue lesions and pain severity in persons with knee osteoarthritis.

INTRODUCTION: Pain is the most common symptom in knee osteoarthritis (OA), a leading cause of chronic disability, and a major source of the disability attributable to OA in general. Pain severity in knee OA is variable, ranging from barely perceptible to immobilizing. The knee lesions that contribute to pain severity have received little attention. OBJECTIVE: To examine whether worse pathology of specific knee tissues - i.e. cartilage, bone (attrition, cysts, bone marrow lesions, and osteophytes), menisci (tears and subluxation), ligaments, and synovium (synovitis/effusion) - is associated with more severe knee pain. METHODS: One hundred and forty-three individuals were recruited from the community with primary (idiopathic) knee OA, with definite tibiofemoral osteophytes in at least one knee, and at least some difficulty with knee-requiring activity. Knee magnetic resonance (MR) images were acquired using coronal T1-weighted spin-echo (SE), sagittal fat-suppressed dual-echo turbo SE, and axial and coronal fat-suppressed, T1-weighted 3D-fast low angle shot (FLASH) sequences. The whole-organ magnetic resonance imaging (MRI) scoring (WORMS) method was used to score knee tissue status. Since summing tissue scores across the entire joint, including regions free of disease, may dilute the ability to detect a true relationship between that tissue and pain severity, we used the score from the worst compartment (i.e. with the poorest cartilage morphology) as our primary approach. Knee pain severity was measured using knee-specific, 100 mm visual analogue scales. In analyses to evaluate the relationship between knee pain severity and lesion score, median quantile regression was used, adjusting for age and body mass index (BMI), in which a 95% CI excluding 0 is significant. RESULTS: The increase in median pain from median quantile regression, adjusting for age and BMI, was significant for bone attrition (1.91, 95% confidence interval (CI) 0.68, 3.13), bone marrow lesions (3.72, 95% CI 1.76, 5.68), meniscal tears (1.99, 95% CI 0.60, 3.38), and grade 2 or 3 synovitis/effusion vs grade 0 (9.82, 95% CI 0.38, 19.27). The relationship with pain severity was of borderline significance for osteophytes and cartilage morphology and was not significant for bone cysts or meniscal subluxation. Ligament tears were too infrequent for meaningful analysis. When compared to the pain severity in knees with high scores for both bone attrition and bone marrow lesions (median pain severity 40 mm), knees with high attrition alone (30 mm) were not significantly different, but knees with high bone marrow lesion without high attrition scores (15 mm) were significantly less painful. CONCLUSION: In persons with knee OA, knee pain severity was associated with subarticular bone attrition, bone marrow lesions, synovitis/effusion, and meniscal tears. The contribution of bone marrow lesions to pain severity appeared to require the presence of bone attrition.

Disease damage and low bone mineral density: an analysis of women with systemic lupus erythematosus ever and never receiving corticosteroids.

OBJECTIVES: To evaluate the relationship between disease damage and bone mineral density (BMD) in women with systemic lupus erythematosus (SLE). METHODS: A cross-sectional study was conducted among 307 women with SLE. Patients attended a single clinic visit that included an interview, physical examination, laboratory testing and BMD measurements (hip and/or lumbar spine). Women were stratified by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology cumulative disease damage index (SDI) > or =1 (Damage) vs SDI=0 (No Damage), and prior use of corticosteroids (CS), yielding four groups: (1) Damage/CS(+) (n=138), (2) Damage/CS(-) (n=23), (3) no Damage/CS(-) (n=100), and (4) no Damage/CS(-) (n=46). RESULTS: Mean age at SLE diagnosis was 32.7 +/- 11.8 yr, 24.4% were African American, 65.0% were premenopausal, and mean SDI +/- S.D. was 1.3 +/- 1.8. In the unadjusted and adjusted models controlling for significant univariate risk factors for osteoporosis, the reference group (Group 1) had significantly lower mean BMD T-scores at the hip and lumbar spine than groups having no disease damage (Groups 3 and 4) independent of CS use status. Similar hip and lumbar spine mean BMD T-scores were observed in women with disease damage with and without CS exposure (Groups 1 and 2). CONCLUSIONS: Women with SLE having disease damage and no CS use had BMD T-scores at the hip and lumbar spine similar to those of women with disease damage and prior CS use. These findings suggest an association between disease damage and lower BMD T-scores in women with SLE.

The role of knee alignment in disease progression and functional decline in knee osteoarthritis.

CONTEXT: Knee osteoarthritis (OA) is a leading cause of disability in older persons. Few risk factors for disease progression or functional decline have been identified. Hip-knee-ankle alignment influences load distribution at the knee; varus and valgus alignment increase medial and lateral load, respectively. OBJECTIVE: To test the hypotheses that (1) varus alignment increases risk of medial knee OA progression during the subsequent 18 months, (2) valgus alignment increases risk of subsequent lateral knee OA progression, (3) greater severity of malalignment is associated with greater subsequent loss of joint space, and (4) greater burden of malalignment is associated with greater subsequent decline in physical function. DESIGN AND SETTING: Prospective longitudinal cohort study conducted March 1997 to March 2000 at an academic medical center in Chicago, Ill. PARTICIPANTS: A total of 237 persons recruited from the community with primary knee OA, defined by presence of definite tibiofemoral osteophytes and at least some difficulty with knee-requiring activity; 230 (97%) completed the study. MAIN OUTCOME MEASURES: Progression of OA, defined as a 1-grade increase in severity of joint space narrowing on semiflexed, fluoroscopically confirmed knee radiographs; change in narrowest joint space width; and change in physical function between baseline and 18 months, compared by knee alignment at baseline. RESULTS: Varus alignment at baseline was associated with a 4-fold increase in the odds of medial progression, adjusting for age, sex, and body mass index (adjusted odds ratio [OR], 4.09; 95% confidence interval [CI], 2.20-7.62). Valgus alignment at baseline was associated with a nearly 5-fold increase in the odds of lateral progression (adjusted OR, 4.89; 95% CI, 2.13-11.20). Severity of varus correlated with greater medial joint space loss during the subsequent 18 months (R = 0.52; 95% CI, 0.40-0.62 in dominant knees), and severity of valgus correlated with greater subsequent lateral joint space loss (R = 0.35; 95% CI, 0.21-0.47 in dominant knees). Having alignment of more than 5 degrees (in either direction) in both knees at baseline was associated with significantly greater functional deterioration during the 18 months than having alignment of 5 degrees or less in both knees, after adjusting for age, sex, body mass index, and pain. CONCLUSION: This is, to our knowledge, the first demonstration that in primary knee OA varus alignment increases risk of medial OA progression, that valgus alignment increases risk of lateral OA progression, that burden of malalignment predicts decline in physical function, and that these effects can be detected after as little as 18 months of observation.

Arthritis prevalence and activity limitations in older adults.

OBJECTIVE: To evaluate the prevalence of arthritis and activity limitations among older Americans by assessing their demographic, ethnic, and economic characteristics. METHODS: Data from the Asset and Health Dynamic Survey Among the Oldest Old (AHEAD), a national probability sample of community-dwelling adults born before 1924, were analyzed cross-sectionally. Arthritis that resulted in a physician's visit or a joint replacement not associated with a hip fracture was ascertained by self-report. RESULTS: The prevalence of arthritis in older adults ranged from 25% in non-Hispanic whites to 40% in non-Hispanic blacks to 44% in Hispanics. A higher prevalence of arthritis was associated with less education as well as lower income and less wealth. The prevalence of limitations in activities of daily living (ADL) among non-Hispanic white, non-Hispanic black, and Hispanic adults who reported arthritis only was 29%, 30%, and 37%, respectively, and increased to 48%, 57%, and 56%, respectively, among those reporting arthritis plus other chronic conditions, after adjustment for age and sex. CONCLUSION: Non-Hispanic black and Hispanic older adults reported having arthritis at a substantially higher frequency than did non-Hispanic whites. In addition, Hispanics reported higher rates of ADL limitations than did non-Hispanic whites with comparable disease burden. Further study is needed to confirm and elucidate the reasons for these racial and economic disparities in older populations.

The mechanism of the effect of obesity in knee osteoarthritis: the mediating role of malalignment.

OBJECTIVE: Obesity is most strongly linked to osteoarthritis (OA) at the knee. Varus malalignment was examined as a possible local mediator that may increase the impact of body weight at the knee, versus the hip or ankle. Compartment load distribution is more equitable in valgus than in varus knees, and valgus knees may better tolerate obesity. We therefore tested whether 1) body mass index (BMI) is correlated with OA severity in varus knees, 2) the BMI-OA severity correlation is weaker in valgus than in varus knees, 3) BMI is correlated with the severity of varus malalignment, and 4) the BMI-medial tibiofemoral OA severity relationship is reduced after controlling for varus malalignment. METHODS: In 300 community-recruited patients with knee OA, 2 groups (varus and valgus) were identified based on dominant knee alignment on a full-limb radiograph, i.e., the angle formed by the intersection of the femoral and tibial mechanical axes. Severity of knee OA was assessed by measurement of the narrowest joint space width on radiographs of knees in a fluoroscopy-confirmed semiflexed position. RESULTS: Alignment direction was symmetric (or neutral in 1 limb) in 87% of patients. One hundred fifty-four patients had varus knees and 115 had valgus knees. BMI correlated with OA severity in the varus group (r = -0.29, P = 0.0009) but not in the valgus group (r = -0.13, P = 0.17). BMI correlated with malalignment in those with varus knees (r = 0.26) but not in those with valgus knees (r = 0.16). The partial correlation of BMI and OA severity, controlling for sex, was reduced from 0.24 (P = 0.002) to 0.04 (P = 0.42) when varus malalignment was added to the model. CONCLUSION: BMI was related to OA severity in those with varus knees but not in those with valgus knees. Much of the effect of BMI on the severity of medial tibiofemoral OA was explained by varus malalignment, after controlling for sex. Whether it precedes or follows the onset of disease, varus malalignment is one local factor that may contribute to rendering the knee most vulnerable to the effects of obesity.

Laxity in healthy and osteoarthritic knees.

OBJECTIVE: Although it is a cause of osteoarthritis (OA) in animal models, laxity in human knee OA has been minimally evaluated. Ligaments become more compliant with age; whether this results in clinical laxity is not clear. In theory, laxity may predispose to OA and/or result from OA. Our goals were to examine the correlation of age and sex with knee laxity in control subjects without OA, compare laxity in uninvolved knees of OA patients with that in older control knees, and examine the relationship between specific features of OA and knee laxity. METHODS: We assessed varus-valgus and anteroposterior laxity in 25 young control subjects, 24 older control subjects without clinical OA, radiographic OA, or a history of knee injury, and 164 patients with knee OA as determined by the presence of definite osteophytes. A device was designed to assess varus-valgus laxity under a constant varus or valgus load while maintaining a fixed knee flexion angle and thigh and ankle immobilization. Radiographic evaluations utilized protocols addressing position, beam alignment, magnification, and landmark definition; the semiflexed position was used, with fluoroscopic confirmation. RESULTS: In the controls, women had greater varus-valgus laxity than did men (3.6 degrees versus 2.7 degrees; 95% confidence interval [95% CI] of difference 0.38, 1.56; P = 0.004), and laxity correlated modestly with age (r = 0.29, P = 0.04). Varus-valgus laxity was greater in the uninvolved knees of OA patients than in older control knees (4.9 degrees versus 3.4 degrees; 95% CI of difference 0.60, 2.24; P = 0.0006). In OA patients, varus-valgus laxity increased as joint space decreased (slope -0.34; 95% CI -0.48, -0.19; P < 0.0001) and was greater in knees with than in knees without bony attrition (5.3 degrees versus 4.5 degrees; 95% CI of difference 0.32, 1.27; P = 0.001). CONCLUSION: Greater varus-valgus laxity in the uninvolved knees of OA patients versus older control knees and an age-related increase in varus-valgus laxity support the concept that some portion of the increased laxity of OA may predate disease. Loss of cartilage/bone height is associated with greater varus-valgus laxity. These results raise the possibility that varus-valgus laxity may increase the risk of knee OA and cyclically contribute to progression.

Increased risk of fracture in patients receiving solid organ transplants.

The success of organ transplantation is related to advances in immunosuppressive therapy. These medications are associated with medical complications including bone damage. The objective of this study was to estimate and compare age, gender-specific fracture incidence between transplant recipients, and a large sample representative of the civilian noninstitutionalized United States population using the 1994 National Health Interview Survey (NHIS). This was a cohort study set in tertiary care centers. Five hundred and thirty-nine individuals who received abdominal organ and 61 heart transplants surviving at least 30 days at our institution from 1986 to 1996 were included in the study. Incident fractures were ascertained by mail, in-person interview, telephone survey, or medical record review. All fractures were verified. Organ-, age-, and gender-specific fracture numbers and rates and person-years of observation, were calculated for the transplant patients. Weighted age- and gender-specific fracture rates from the 1994 NHIS were applied to the number of person-years of observation for each organ-specific age and gender category of transplant patients to generate an expected number of fractures. The ratio of observed to expected number of fractures was used to compare fracture experience of transplant patients to that of the national sample from the 1994 NHIS. Fifty-six of 600 (9.3%) patients had at least one fracture following 1221 person-years of observation. The sites of initial symptomatic fracture were as follows: foot (n = 22), arm (n = 8), leg (n = 7), ribs (n = 6), hip (n = 4), spine (n = 3), fingers (n = 3), pelvis (n = 2), and wrist (n = 1). Fracture incidence was 13 times higher than expected in male heart recipients age 45-64 years; nearly 5 times higher in male kidney recipients age 25-44 and age 45-64 years; and 18 times and 34 times higher in female kidney recipients age 25-44 years and 45-64 years compared with NHIS data. We have shown an increased incidence of fractures and estimated the magnitude of this problem in patients undergoing solid organ transplantation. Our work defines the need for a long-term prospective study of fracture risk in these patients.

Does laxity alter the relationship between strength and physical function in knee osteoarthritis?

OBJECTIVE: Since strengthening interventions have had a lower-than-expected impact on patient function in studies of knee osteoarthritis (OA) and it is known that laxity influences muscle activity, this study examined whether the relationship between strength and function is weaker in the presence of laxity. METHODS: One hundred sixty-four patients with knee OA were studied. Knee OA was defined by the presence of definite osteophytes, and patients had to have at least a little difficulty with knee-requiring activities. Tests were performed to determine quadriceps and hamstring strength, varus-valgus laxity, functional status (Western Ontario and McMaster Universities Osteoarthritis Index Physical Functioning subscale [WOMAC-PF] and chair-stand performance), body mass index, and pain. High and low laxity groups were defined as above and below the sample median, respectively. RESULTS: Strength and chair-stand rates correlated (r = 0.44 to 0.52), as did strength and the WOMAC-PF score (r = -0.21 to -0.36). In multivariate analyses, greater laxity was consistently associated with a weaker relationship between strength (quadriceps or hamstring) and physical functioning (chair-stand rate or WOMAC-PF score). CONCLUSION: Varus-valgus laxity is associated with a decrease in the magnitude of the relationship between strength and physical function in knee OA. In studies examining the functional and structural consequences of resistance exercise in knee OA, stratification of analyses by varus-valgus laxity should be considered. The effect of strengthening interventions in knee OA may be enhanced by consideration of the status of the passive restraint system.

Knee adduction moment, serum hyaluronan level, and disease severity in medial tibiofemoral osteoarthritis.

OBJECTIVE: The adduction moment at the knee during gait is the primary determinant of medial-to-lateral load distribution. If the adduction moment contributes to progression of osteoarthritis (OA), then patients with advanced medial tibiofemoral OA should have higher adduction moments. The present study was undertaken to investigate the hypothesis that the adduction moment normalized for weight and height is associated with medial tibiofemoral OA disease severity after controlling for age, sex, and pain level, and to examine the correlation of serum hyaluronan (HA) level with disease severity and with the adduction moment in a subset of patients. METHODS: Fifty-four patients with medial tibiofemoral OA underwent gait analysis and radiographic evaluation. Disease severity was assessed using the Kellgren-Lawrence (K-L) grade and medial joint space width. In a subset of 23 patients with available sera, HA was quantified by sandwich enzyme-linked immunosorbent assay. Pearson correlations, a random effects model, and multivariate regression models were used. RESULTS: The adduction moment correlated with the K-L grade in the left and right knees (r = 0.68 and r = 0.60, respectively), and with joint space width in the left and right knees (r = -0.45 and r = -0.47, respectively). The relationship persisted after controlling for age, sex, and severity of pain. The partial correlation between K-L grade and adduction moment was 0.71 in the left knees and 0.61 in the right knees. For every 1.0-unit increase in adduction moment, there was a 0.63-mm decrease in joint space width. In the subset of patients in whom serum HA levels were measured, HA levels correlated with medial joint space width (r = -0.55), but not with the adduction moment. CONCLUSION: There is a significant relationship between the adduction moment and OA disease severity. Serum HA levels correlate with joint space width but not with the adduction moment. Longitudinal studies will be necessary to determine the contribution of the adduction moment, and its contribution in conjunction with metabolic markers, to progression of medial tibiofemoral OA.

Impact of joint impairment on disability-specific domains at four years.

The objective of this study was to assess the longitudinal impact of joint impairment on overall disability and crossing domain-specific thresholds for physical activity, mobility, dexterity, instrumental activities of daily living (IADL), and activities of daily living (ADL) that are associated with use of long-term care. This 4-year longitudinal study observed 484 persons older than age 60. Logistic regression assessed the contribution of demographics, psychological mediators, lower- and upper-extremity joint impairment, and comorbidities to increased domain-specific self-reported disability above a threshold associated with use of long-term care. Lower-extremity joint impairment and age predicted crossing thresholds by year 4 in physical activity, mobility, IADL, and ADL disability that were associated with use of long-term care. Lower-extremity joint impairment is a strong risk factor for future disability that is associated with use of long-term care.

Disability in activities of daily living: patterns of change and a hierarchy of disability.

OBJECTIVES: This paper examines longitudinal data over 6 years to evaluate incidence rates of disability and the pattern of dependency in activities of daily living. METHODS: The Longitudinal Study of Aging (n = 5151) was used to evaluate incidence of disability in activities of daily living; biennial interview data from 1984 through 1990 were used. The median age to disability onset for individual activities was estimated from survival analysis. A prevalent ordering of incident disability was identified from patterns of disability onset within individuals. RESULTS: The progression of incident disability among the elderly supported by longitudinal data, based on both the ordering of median ages to disability onset and patterns of incident disability, was as follows: walking, bathing, transferring, dressing, toileting, feeding. Gender differences were found in disability incidence rates. CONCLUSIONS: This study provides a mathematical picture of physical functioning as people age. These findings, based on longitudinal data, indicate a different hierarchical structure of disability than found in previous reports using cross-sectional data. Furthermore, the study documents gender differences in incident impairment, which indicate that although women outlive men, they spend more time in a disabled state.

A model-based approach to estimate the AIDS-free time distribution in homosexual men using longitudinal data.

A model-based approach is developed to estimate the distribution of time from seroconversion to diagnosis with acquired immunodeficiency syndrome (AIDS) as a function of selected time-dependent covariates. The approach is applied to longitudinal data collected over 4 years of follow-up from 450 men seropositive for the human immunodeficiency virus (90 AIDS cases) and 62 seroconverters (nine AIDS cases) participating in the Chicago part of the Multicenter AIDS Cohort Study. Because of the periodic nature of monitoring, the seroconversion time is interval-censored for seroconverters and left-censored for seroprevalent cohort members; the end-point is right-censored for 413 individuals. Since serological monitoring is not continuous but only at regularly scheduled visit times, a model for the discrete hazard rate (DHR) is proposed that is a generalized linear model that relates the DHR to the covariate history through the complementary log-log link. Classification trees are used for preliminary screening of covariates to identify predictors of AIDS that should be incorporated into the DHR model. The missing seroconversion times for all men are imputed 100 times to obtain 100 completed datasets from which the parameters of the DHR are then estimated using the maximum-likelihood method. The final DHR model includes the following infection progression (marker) variables: CD4%, hemoglobin, p24 antigen, and CD4% x p24 antigen interaction. Using this DHR model, the discrete survival distribution of AIDS-free time is estimated for the given population. The jackknife procedure is used to assess the precision of the estimated survival distribution.

Predicting stroke inpatient rehabilitation outcome using a classification tree approach.

A classification tree, a nonparametric statistical analysis, was used to develop decision rules to predict a favorable inpatient stroke rehabilitation outcome. Descriptive and functional status data collected on admission from 225 patients were the predictor variables. Favorable outcome was defined as having met three criteria: discharged to community, survival greater than 3 months postdischarge, and no more than minimal physical assistance required in functional activities on discharge. The classification tree correctly classified 88% of the sample using only four of the predictor variables (level of independence in Toilet Management, Bladder Management, and Toilet Transfer, and adequacy of Financial Resources). The cross validation error rate was 18%. The advantages of the classification tree approach over parametric methods are that it is desirable for ordinal data, it readily identifies the interactions among predictor variables, the results are easily communicated, and it provides additional insights into the factors that predict outcome.

Mammary stimulation test predicts preterm birth in nulliparous women.

OBJECTIVE: This prospective clinical trial was designed to assess the ability of the mammary stimulation test to predict preterm birth in a private nulliparous population. STUDY DESIGN: The mammary stimulation test was performed between 26 and 28 weeks' gestation by 267 nulliparous women with singleton pregnancies. Test results were blinded to both patient and referring physician. Pregnancy outcome data were collected from the perinatal database and medical records. RESULTS: The mammary stimulation test was positive in 45 of 266 (17%) patients. Delivery occurred at < 37 weeks in 27 patients (10.2%) and at < 34 weeks in five (1.9%). The mammary stimulation test demonstrated a sensitivity of 37%, a specificity of 84%, a positive predictive value of 20%, and a negative predictive value of 92% for delivery at < 37 weeks' gestation. For delivery at < 34 weeks' gestation the mammary stimulation test had a sensitivity of 60%, a specificity of 82%, a positive predictive value of 6%, and a negative predictive value 99%. The odds ratio for delivery at < 37 weeks was 3.0 (95% confidence interval 1.3, 7.1), and for delivery at < 34 weeks the odds ratio was 7.0 (95% confidence interval 1.1, 43.0). One third of preterm deliveries were secondary to idiopathic preterm labor, and the mammary stimulation test was positive in 77.8% (seven of nine) of these pregnancies. Patients with a positive test were more likely to require observation in labor and delivery for preterm uterine contractions (34% vs 4.3%, p < 0.01), and they were more likely to demonstrate change at cervical examination (14% vs 2%, p < 0.01). CONCLUSION: In this population traditionally considered to be at low risk for preterm birth a positive mammary stimulation test was useful in identifying patients at risk for preterm uterine activity and preterm birth. Equally important was the identification of women who were at low risk for preterm birth.