Classification of musculoskeletal pain severity in the Constances cohort: a latent class analysis

Severe forms of musculoskeletal pain (MSP) with functional and occupational consequences are of growing concern in the context of an aging workforce and longer working lives. This study aimed to define a classification of MSP severity in the French population and to examine associations between MSP severity and sociodemographic characteristics and lifetime occupational biomechanical exposures.

We conducted cross-sectional analyses in the Constances cohort, among participants aged 45 years and older. Symptom duration of MSP in 6 body regions, functional limitations and job loss/early retirement due to MSP were self-reported. Latent class analysis was performed separately for men and women. The resulting classification was described according to sociodemographic characteristics and 3 lifetime occupational biomechanical exposures, and its association with these variables was estimated using multinomial logistic regression.

A total of 74,581 participants (35,919 men and 38,662 women) were included. Four classes were identified for men and women: "Absence of MSP" (men = 51.4%; women = 41.3%), "Subacute MSP without functional limitations" (24.4%; 27.7%), "Chronic MSP with moderate functional limitations" (14.2%; 16.8%), and "Permanent MSP with severe functional limitations and occupational consequences" (10.0%; 14.2%). Compared with the "Absence of MSP" class, the "Permanent MSP with severe functional limitations and occupational consequences" class was associated with lifetime occupational biomechanical exposures: forceful work/manual handling of loads (men: OR 1.63, 95% CI 1.48 to 1.79; women: 1.31, 95% CI 1.17 to 1.45), strenuous postures (1.67, 1.51 to 1.85; 1.67, 1.56 to 1.79), and mechanical vibrations (1.59, 1.44 to 1.75; 1.61, 1.44 to 1.81). Similar associations were observed for the other MSP severity classes, except for mechanical vibrations, which were not associated with the "Chronic MSP with moderate functional limitations" class among women.

This study defined a classification of MSP severity based on symptom duration, functional limitations, and occupational consequences. Four classes were identified in both men and women, describing a progressive gradient of severity. The most severe class, comprising 10% of men and 14% of women, was associated with each of the 3 lifetime occupational biomechanical exposures. These findings provide quantitative data on the different forms of MSP and on the populations most affected by the severe forms.