1、,A Case-Control Study of Biomechanical and Psychosocial Risk Factors for Occupational Low-Back Pain,Michael S. Kerr, PhD Institute for Work & Health Toronto, Ontario, CANADA,PREMUS 2001, Amsterdam,Kerr et al. (2001) Am J Pub Health 91:1069-1075,2,Study Collaborators,Institute for Work & Health: Kerr
2、 MS, Frank JW, Shannon HS, Bombardier CUniversity of Waterloo: Norman RW, Wells RW, Neumann P,General Motors: Mr. Elmer Beddome CAW: Mr. John Graham,The Ontario Universities Back Pain Study (OUBPS) Group,Andrews D, Beaton DE, Dobbyn M, Edmonstone E, Ferrier S, Hogg-Johnson S, Ingelman P, Mondlock M,
3、 Peloso P, Smith J, Stanfield SA, Tarasuk V, Woo H,3,Why a case-control study?,Uncertainty about role of physical demands necessitated concentration of effort on developing valid workplace measures Cohort model required multiple measures at multiple times to assess valid exposure,Does a prospective
4、cohort study with limited (e.g. once only) exposure assessment really provide more rigorous evidence than a case-control study with more detailed assessments?,4,Research Question,After controlling for individual characteristics, what are the main work-related biomechanical and psychosocial risk fact
5、ors for reported low-back pain?,5,The GM Study of Low-back Pain,baseline,questionnaire and,physical exam,10,000 car and truck plant workers (hourly-paid),random selection (job-matched),accrued via workplace health stations,conducted at home,physical demands,assessment,CASES,workers without LBP,STUDY
6、 POPULATION,workers,with,LBP,CONTROLS,Incidence density sampling,at work doing usual job,video, EMG, checklists, posture,(n=137),(n=179),(n2=65),6,How did we control for Bias?,Directly measured physical demands data rather than self-report Job-matched controls used to examine potential recall bias (
7、none observed) Used newly incident cases rather than prevalent cases Compared cases with non-participating compensation claimants (no differences) A priori reduction in variables eligible for regression modeling (multi-methods),7,Summary of Key Risk Factors,(after adjusting for individual characteri
8、stics),8,Main Conclusions,Consistency and strength indicates biomechanical load increases LBP risk Psychosocial factors also shown to be associated with reporting LBP Job dissatisfaction not a risk factor for reporting LBP in this setting Psychosocial instruments (especially Karaseks demands scale)
9、may require further refinement for MSK studies,9,For additional information please contact:,Mickey Kerr The Institute for Work & Health 481 University Ave., Suite 800 Toronto, ON M5G 2E9 Phone: (416) 927-2027 Fax: (416)-927-4167 Website: http:/www.iwh.on.ca E-mail: infoiwh.on.ca,The Institute for Wo
10、rk & Health operates with the support of the Ontario Workplace Safety & Insurance Board,Kerr et al. (2001) Am J Pub Health 91:1069-1075,10,Study Strengths,Directly measured physical demands data combined with (basic) physical exam and interview-assisted psychosocial data for individual subjects Comp
11、rehensive workplace job demands assessments (generalizable i.e. not specific to automobile manufacturing) Well defined study base for subject selection,11,Study Weaknesses,Modest participation rate (approx 60%) Relied on workplace reporting mechanism to identify cases Self-report only for psychosoci
12、al factors Case-control designBut does a prospective cohort study with limited once only exposure assessment really provide more rigorous evidence than a case-control study with more detailed assessments?,12,SF-36, Health-related quality of life,Physical Function,Role Physical,Bodily Pain,Social Fun
13、ction,Vitality,Role Emotional,Mental Health,General Health,Were cases and controls comparable except for LBP?,sd from male reference population,Ref: Garrat et al. (1993) BMJ 306:1440-4,13,INDIVIDUAL Characteristics,Age, height, weight, body mass index, sex education, marital status, preschool childr
14、en, main wage earner, non-occupational physical activity, smoking, alcohol consumption,STUDY VARIABLES - 1,14,BIOMECHANICAL Factors,Peak Forces:compression; shear; hand forceCumulative Forces:average and integrated compression;Low-level (static) Forces:compressionPosture and Movement:peak flexion; t
15、ime non-neutral; trunk kinematics,(reduced a priori to about 20 key variables, NO EMG),STUDY VARIABLES - 2,15,STUDY VARIABLES - 3,PSYCHOPHYSICAL Factors,self-rated physical exertion measures distinct from “objective“ measurements of physical demands analyses, but may also have additional role to pla
16、y over and above the measured demands e.g. tolerance levels, “job stress“, etc.,16,Karasek-Theorell Job Content Instrument “psychological demand“, decision latitude, supervisor support, coworker support, workplace social environment, job self-identity - job dissatisfaction, mastery, empowerment, sta
17、tus inconsistency (“over-education“),STUDY VARIABLES - 4,PSYCHOSOCIAL Factors,17,CASE Definition,Full-time, hourly-paid worker with “sprain-strain” LBP (reported to nursing stations)No lost-time or WCB claim requirementNo previous worksite LBP report (90 days),18,STUDY SETTING,GM-Oshawa autoplex,65
18、km east of Toronto Total hourly-paid work force approx. 12,000 3 Divisions: Car Assembly (7,000)Truck Assembly (3,000)Fabrications N/A,Nursing stations handle ALL WCB reports as well as most other health problems occurring at work-site Truck = 1 station; Car = 4 stations,19,SUBJECT ENROLMENT,(Voluntary),179,137,65,Random controls,Cases,A total of 381 subjects enrolled in the study,Job-matched controls (used for proxy data),20,Possible Biological Mechanisms,
