Karim M. Khan

Bio: Karim M. Khan is an academic researcher from University of British Columbia. The author has contributed to research in topics: Osteoporosis & Tendinopathy. The author has an hindex of 82, co-authored 352 publications receiving 23388 citations. Previous affiliations of Karim M. Khan include University of Melbourne & Norwegian School of Sport Sciences.

Meta-analysis of the impact of 9 medication classes on falls in elderly persons.

Abstract: Background: There is increasing recognition that the use of certain medications contributes to falls in seniors. Our objective was to update a previously completed meta-analysis looking at the association of medication use and falling to include relevant drug classes and new studies that have been completed since a previous meta-analysis. Methods: Studies were identified through a systematic search of English-language articles published from 1996 to 2007. We identified studies that were completed on patients older than 60 years, looking at the association between medication use and falling. Bayesian methods allowed us to combine the results of a previous metaanalysis with new information to estimate updated Bayesian odds ratios (ORs) and 95% credible intervals (95% CrIs) Results: Of 11 118 identified articles, 22 met our inclusion criteria. Meta-analyses were completed on 9 unique drug classes, including 79 081 participants, with the following Bayesian unadjusted OR estimates: antihypertensive agents, OR, 1.24 (95% CrI, 1.01-1.50); diuretics, OR, 1.07 (95% CrI, 1.01-1.14); -blockers, OR, 1.01 (95% CrI, 0.86-1.17); sedatives and hypnotics, OR, 1.47 (95% CrI, 1.35-1.62); neuroleptics and antipsychotics, OR, 1.59 (95% CrI, 1.37-1.83); antidepressants, OR, 1.68 (95% CrI, 1.47-1.91); benzodiazepines, OR, 1.57 (95% CrI, 1.431.72); narcotics, OR, 0.96 (95% CrI, 0.78-1.18); and nonsteroidal anti-inflammatory drugs, OR, 1.21 (95% CrI, 1.01-1.44). The updated Bayesian adjusted OR estimates for diuretics, neuroleptics and antipsychotics, antidepressants, and benzodiazepines were 0.99 (95% CrI, 0.78-1.25), 1.39 (95% CrI, 0.94-2.00), 1.36 (95% CrI, 1.13-1.76), and 1.41 (95% CrI, 1.20-1.71), respectively. Stratification of studies had little effect on Bayesian OR estimates, with only small differences in the stratified ORs observed across population (for -blockers and neuroleptics and antipsychotics) and study type (for sedatives and hypnotics, benzodiazepines, and narcotics). An increased likelihood of falling was estimated for the use of sedatives and hypnotics, neuroleptics and antipsychotics, antidepressants, benzodiazepines, and nonsteroidal anti-inflammatory drugs in studies considered to have “good” medication and falls ascertainment. Conclusion: The use of sedatives and hypnotics, antidepressants, and benzodiazepines demonstrated a significant association with falls in elderly individuals.

Histopathology of common tendinopathies. Update and implications for clinical management.

Abstract: Tendon disorders are a major problem for participants in competitive and recreational sports. To try to determine whether the histopathology underlying these conditions explains why they often prove recalcitrant to treatment, we reviewed studies of the histopathology of sports-related, symptomatic Achilles, patellar, extensor carpi radialis brevis and rotator cuff tendons. The literature indicates that healthy tendons appear glistening white to the naked eye and microscopy reveals a hierarchical arrangement of tightly packed, parallel bundles of collagen fibres that have a characteristic reflectivity under polarised light. Stainable ground substance (extracellular matrix) is absent and vasculature is inconspicuous. Tenocytes are generally inconspicuous and fibroblasts and myofibroblasts absent. In stark contrast, symptomatic tendons in athletes appear grey and amorphous to the naked eye and microscopy reveals discontinuous and disorganised collagen fibres that lack reflectivity under polarised light. This is associated with an increase in the amount of mucoid ground substance, which is confirmed with Alcian blue stain. At sites of maximal mucoid change, tenocytes, when present, are plump and chondroid in appearance (exaggerated fibrocartilaginous metaplasia). These changes are accompanied by the increasingly conspicuous presence of cells within the tendon tissue, most of which have a fibroblastic or myofibroblastic appearance (smooth muscle actin is demonstrated using an avidin biotin technique). Maximal cellular proliferation is accompanied by prominent capillary proliferation and a tendency for discontinuity of collagen fibres in this area. Often, there is an abrupt discontinuity of both vascular and myofibroblastic proliferation immediately adjacent to the area of greatest abnormality. The most significant feature is the absence of inflammatory cells. These observations confirm that the histopathological findings in athletes with overuse tendinopathies are consistent with those in tendinosis--a degenerative condition of unknown aetiology. This may have implications for the prognosis and timing of a return to sport after experiencing tendon symptoms. As the common overuse tendon conditions are rarely, if ever, caused by 'tendinitis', we suggest the term 'tendinopathy' be used to describe the common overuse tendon conditions. We conclude that effective treatment of athletes with tendinopathies must target the most common underlying histopathology, tendinosis, a noninflammatory condition.

Clinical Sports Medicine

Abstract: Clinical Sports Medicine has been fully updated from the popular 2nd edition (2000). It is even more practical, now superbly illustrated, easy-to-read and packed with substantially updated and new material. There are samples of several chapters online including the whole "Pain in the Achilles region" chapter. This book describes a completely symptom-oriented approach to treating clinical problems.

The VISA-A questionnaire: a valid and reliable index of the clinical severity of Achilles tendinopathy

Abstract: Background—There is no disease specific, reliable, and valid clinical measure of Achilles tendinopathy. Objective—To develop and test a questionnaire based instrument that would serve as an index of severity of Achilles tendinopathy. Methods—Item generation, item reduction, item scaling, and pretesting were used to develop a questionnaire to assess the severity of Achilles tendinopathy. The final version consisted of eight questions that measured the domains of pain, function in daily living, and sporting activity. Results range from 0 to 100, where 100 represents the perfect score. Its validity and reliability were then tested in a population of non-surgical patients with Achilles tendinopathy (n = 45), presurgical patients with Achilles tendinopathy (n = 14), and two normal control populations (total n = 87). Results—The VISA-A questionnaire had good test-retest (r = 0.93), intrarater (three tests, r = 0.90), and interrater (r = 0.90) reliability as well as good stability when compared one week apart (r = 0.81). The mean (95% confidence interval) VISA-A score in the non-surgical patients was 64 (59‐69), in presurgical patients 44 (28‐60), and in control subjects it exceeded 96 (94‐99). Thus the VISA-A score was higher in non-surgical than presurgical patients (p = 0.02) and higher in control subjects than in both patient populations (p<0.001). Conclusions—The VISA-A questionnaire is reliable and displayed construct validity when means were compared in patients with a range of severity of Achilles tendinopathy and control subjects. The continuous numerical result of the VISA-A questionnaire has the potential to provide utility in both the clinical setting and research. The test is not designed to be diagnostic. Further studies are needed to determine whether the VISA-A score predicts prognosis. (Br J Sports Med 2001;35:335‐341)

Achilles tendon disorders: etiology and epidemiology.

Abstract: The Achilles tendon is the strongest tendon in the human body. Because most Achilles tendon injuries take place in sports and there has been a general increase in popularity of sporting activities, the number and incidence of the Achilles tendon overuse injuries and complete, spontaneous ruptures has increased in the industrialized countries during the last decades. The most common clinical diagnosis of Achilles overuse injuries is tendinopathy. The basic etiology of the Achilles tendinopathy is known to be multi-factorial. Although histopathologic studies have shown that ruptured Achilles tendons have clear degenerative changes before the rupture, many Achilles tendon ruptures take place suddenly without any preceding signs or symptoms.

Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory, Musculoskeletal, and Neuromotor Fitness in Apparently Healthy Adults: Guidance for Prescribing Exercise

Abstract: The purpose of this Position Stand is to provide guidance to professionals who counsel and prescribe individualized exercise to apparently healthy adults of all ages. These recommendations also may apply to adults with certain chronic diseases or disabilities, when appropriately evaluated and advised by a health professional. This document supersedes the 1998 American College of Sports Medicine (ACSM) Position Stand, "The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Healthy Adults." The scientific evidence demonstrating the beneficial effects of exercise is indisputable, and the benefits of exercise far outweigh the risks in most adults. A program of regular exercise that includes cardiorespiratory, resistance, flexibility, and neuromotor exercise training beyond activities of daily living to improve and maintain physical fitness and health is essential for most adults. The ACSM recommends that most adults engage in moderate-intensity cardiorespiratory exercise training for ≥30 min·d on ≥5 d·wk for a total of ≥150 min·wk, vigorous-intensity cardiorespiratory exercise training for ≥20 min·d on ≥3 d·wk (≥75 min·wk), or a combination of moderate- and vigorous-intensity exercise to achieve a total energy expenditure of ≥500-1000 MET·min·wk. On 2-3 d·wk, adults should also perform resistance exercises for each of the major muscle groups, and neuromotor exercise involving balance, agility, and coordination. Crucial to maintaining joint range of movement, completing a series of flexibility exercises for each the major muscle-tendon groups (a total of 60 s per exercise) on ≥2 d·wk is recommended. The exercise program should be modified according to an individual's habitual physical activity, physical function, health status, exercise responses, and stated goals. Adults who are unable or unwilling to meet the exercise targets outlined here still can benefit from engaging in amounts of exercise less than recommended. In addition to exercising regularly, there are health benefits in concurrently reducing total time engaged in sedentary pursuits and also by interspersing frequent, short bouts of standing and physical activity between periods of sedentary activity, even in physically active adults. Behaviorally based exercise interventions, the use of behavior change strategies, supervision by an experienced fitness instructor, and exercise that is pleasant and enjoyable can improve adoption and adherence to prescribed exercise programs. Educating adults about and screening for signs and symptoms of CHD and gradual progression of exercise intensity and volume may reduce the risks of exercise. Consultations with a medical professional and diagnostic exercise testing for CHD are useful when clinically indicated but are not recommended for universal screening to enhance the safety of exercise.

Health benefits of physical activity: the evidence

Abstract: The primary purpose of this narrative review was to evaluate the current literature and to provide further insight into the role physical inactivity plays in the development of chronic disease and premature death. We confirm that there is irrefutable evidence of the effectiveness of regular physical activity in the primary and secondary prevention of several chronic diseases (e.g., cardiovascular disease, diabetes, cancer, hypertension, obesity, depression and osteoporosis) and premature death. We also reveal that the current Health Canada physical activity guidelines are sufficient to elicit health benefits, especially in previously sedentary people. There appears to be a linear relation between physical activity and health status, such that a further increase in physical activity and fitness will lead to additional improvements in health status.

Thinking fast and slow.

Abstract: In 1974 an article appeared in Science magazine with the dry-sounding title “Judgment Under Uncertainty: Heuristics and Biases” by a pair of psychologists who were not well known outside their discipline of decision theory. In it Amos Tversky and Daniel Kahneman introduced the world to Prospect Theory, which mapped out how humans actually behave when faced with decisions about gains and losses, in contrast to how economists assumed that people behave. Prospect Theory turned Economics on its head by demonstrating through a series of ingenious experiments that people are much more concerned with losses than they are with gains, and that framing a choice from one perspective or the other will result in decisions that are exactly the opposite of each other, even if the outcomes are monetarily the same. Prospect Theory led cognitive psychology in a new direction that began to uncover other human biases in thinking that are probably not learned but are part of our brain’s wiring.

Systematic review of the health benefits of physical activity and fitness in school-aged children and youth

Abstract: The purpose was to: 1) perform a systematic review of studies examining the relation between physical activity, fitness, and health in school-aged children and youth, and 2) make recommendations based on the findings. The systematic review was limited to 7 health indicators: high blood cholesterol, high blood pressure, the metabolic syndrome, obesity, low bone density, depression, and injuries. Literature searches were conducted using predefined keywords in 6 key databases. A total of 11,088 potential papers were identified. The abstracts and full-text articles of potentially relevant papers were screened to determine eligibility. Data was abstracted for 113 outcomes from the 86 eligible papers. The evidence was graded for each health outcome using established criteria based on the quantity and quality of studies and strength of effect. The volume, intensity, and type of physical activity were considered. Physical activity was associated with numerous health benefits. The dose-response relations observed in observational studies indicate that the more physical activity, the greater the health benefit. Results from experimental studies indicate that even modest amounts of physical activity can have health benefits in high-risk youngsters (e.g., obese). To achieve substantive health benefits, the physical activity should be of at least a moderate intensity. Vigorous intensity activities may provide even greater benefit. Aerobic-based activities had the greatest health benefit, other than for bone health, in which case high-impact weight bearing activities were required. The following recommendations were made: 1) Children and youth 5-17 years of age should accumulate an average of at least 60 minutes per day and up to several hours of at least moderate intensity physical activity. Some of the health benefits can be achieved through an average of 30 minutes per day. [Level 2, Grade A]. 2) More vigorous intensity activities should be incorporated or added when possible, including activities that strengthen muscle and bone [Level 3, Grade B]. 3) Aerobic activities should make up the majority of the physical activity. Muscle and bone strengthening activities should be incorporated on at least 3 days of the week [Level 2, Grade A].