Validity of self-reported duration of work postures obtained by interview. MUSIC-Norrtälje Study Group.

The aim of the study was to validate interview data concerning the duration of four work postures (1) sitting, (2) standing/walking with hands above shoulder level, (3) standing/walking with hands between shoulder and knuckle level, and (4) standing/walking with hands below knuckle level. The self-reported time spent in each posture was tested in relation to observations and technical measurements in 20 subjects during two full working days. The linear relationships between self-reports and observations were strong for the three postures; sitting (r2 = 0.55), hands above shoulder level (r2 = 0.58) and hands below knuckle level (r2 = 0.69). Thus, using this interview technique, self-reports concerning time spent in (1) sitting, (2) standing/walking with hands above shoulder level and, (3) standing/walking with hands below knuckle level may be accurate enough for studying these work postures in epidemiological studies.

Differences in the association between psychosocial work conditions and physical work load in female- and male-dominated occupations. MUSIC-Norrtälje Study Group.

This study investigated whether there is a relationship between high physical work load and adverse psychosocial work factors, and whether this relationship is different for women and men. Separate analyses for female registered nurses and assistant nurses were made because these are common occupations involving high physical and psychological demands. This study was part of the MUSIC-Norrtälje study, a population study with the overall aim of identifying risk factors for musculoskeletal disorders. The respondents, 1423 gainfully employed men and women, were randomly selected from the study population. The exposure assessments referred to a typical workday during the previous 12 months. Physical exposure was investigated by interview, psychosocial work factors by interview and questionnaire. For the women, but not the men, mainly routine work and a job strain situation, according to the model of Karasek and Theorell, increased the probability of having a high physical work load, assessed as a time-weighted average of energy expenditure in multiples of the resting metabolic rate. Results indicated that in female-dominated occupations, high physical work load might also imply adverse psychosocial conditions. A higher frequency of high physical work load and job strain was observed among assistant nurses compared with registered nurses. Covariance between physical and psychosocial demands makes it difficult to determine the relative influence of each in health problems. Results of the present study imply that this is a larger problem in studies of women than men.

Interview versus questionnaire for assessing physical loads in the population-based MUSIC-Norrtälje Study.

BACKGROUND: MUSIC-Norrtälje study is a case-referent study, the aim of which is to find risk and health factors for low back and neck/shoulder disorders. In this part of the study, the interview technique and the self-administered questionnaire used for assessment of physical loads are described and the inter-method reliability of parts of the self-administered questionnaire is estimated. The distribution of exposure levels in a general population is also described. METHODS: The study period was three years from November 1993 to November 1996, and the study subjects totaled 2,480 persons (813 female and 610 male referents, 380 female and 315 male low back cases, 252 female and 106 male neck/shoulder cases). The interview concerned "a typical working day" during the preceding 12 months and comprised assessment of energy expenditure, work postures, and manual materials handling for work and leisure time, including regular sport activities. The self-administered questionnaire comprised 18 questions, each covering 5 different points of time: right now, 5, 10, 15, 20 years ago. The answers to eight of the questions about current conditions were compared to corresponding interview responses. The interview was considered as the "gold standard." RESULTS: Ninety-eight percent of the subjects completed the interview without any great difficulties. According to the interview, the distributions of different exposure levels were generally positively skewed, i.e., the frequency of highly exposed subjects was low in the study base. The correlation between interview and questionnaire responses among the referents was high for time spent "sitting at work" (r = 0.82), "VDU work" (r = 0.87), and work related "motor vehicle driving" (r = 0.80). The correlation was moderate for work-related "hands above shoulder level" (rs = 0.63), and "hands below knee level (trunk flexion)" (rs = 0.66). The correlation was lower for leisure time activities such as "domestic work" (r = 0.55), "time for own activities" (r = 0.39), and "sitting during leisure time" (r = 0.38). Subjects seeking care for low back or neck/shoulder disorder estimated equally correctly or not, as had the referents. However, non-differential misclassification was present in all questions, which will attenuate observed estimates of the relative risk. CONCLUSIONS: Even though interview data are preferable, questionnaire data may be useful for assessing well-defined work tasks and for "sitting at work."