Background: This study was designed to investigate the prevalence of
osteoarthritis in the carpometacarpal joint of the thumb in adults thirty
years of age or older in Finland.
Methods: Between 1978 and 1980, a representative population sample
of 8000 Finns thirty years of age or older were invited to have a
comprehensive health examination; 90% accepted. Hand radiographs were made of
3595 subjects. Since the examination, the subjects have been followed
systematically to assess work disability and mortality by reviewing registers
covering the whole population.
Results: The age-adjusted prevalence of thumb carpometacarpal
osteoarthritis of Kellgren grade 2, 3, or 4 was 7% for men and 15% for women.
After adjustment for age, sex, and other alleged risk factors, body mass index
was found to be directly proportional to the prevalence of thumb
carpometacarpal osteoarthritis in both sexes. The adjusted odds ratio was 1.29
(95% confidence interval, 1.15 to 1.43) per 5-kg/m2 increment in
body mass index. No significant association was found between the physical
workload history and thumb carpometacarpal osteoarthritis. Restricted mobility
of the thumb and local tenderness and swelling were frequently found in
conjunction with radiographic evidence of thumb carpometacarpal
osteoarthritis. Advanced (grade-3 or 4) thumb carpometacarpal osteoarthritis
predicted the total mortality rate in men (adjusted relative risk, 1.32; 95%
confidence interval, 1.03 to 1.69). Radiographic signs of thumb
carpometacarpal osteoarthritis did not predict work disability.
Conclusions and Clinical Relevance: Obesity is a strong determinant
of thumb carpometacarpal osteoarthritis in both sexes. The effect of thumb
carpometacarpal osteoarthritis on disability and mortality in the general
population is modest. Because of the rarity of ensuing disability,
carpometacarpal osteoarthritis of the thumb is likely to be underdiagnosed in
Level of Evidence: Prognostic study, Level II-1
(retrospective study). See Instructions to Authors for a complete description
of levels of evidence.