Dr. Shin-Liang Pan of National Taiwan University College of Medicine, Taipei, stated that, "This population-based follow-up study showed an increased risk of developing adhesive capsulitis of shoulder in patients with newly diagnosed diabetes. Clinicians should be alert to the possibility of musculoskeletal complication in patients with diabetes." The researchers noted that in some cases of ACS, it had been etiologically linked to previous trauma of the shoulder, but most are considered to be idiopathic.
Moreover, "most previous studies were performed on selected clinical series of patients rather than the recruitment of study subjects from the general population, which may result in unrepresentative, biased findings of the association."
The new findings are from a population-based, age- and sex-matched longitudinal follow-up study using information from the complete National Health Insurance claim database in Taiwan from 2000 to 2003.
The investigators examined data on more than 78,000 patients with a principal diagnosis of diabetes and over 236,000 matched controls without diabetes. Patients with a previous diagnosis of diabetes or ACS were excluded.
During three years of follow-up, 946 (1.2%) of the diabetics developed ACS, significantly more than the 0.95% proportion (2254 subjects) in the non-diabetic group. The crude hazard ratio was 1.333 and after adjustment for age, sex, and dyslipidemia, it continued to be significantly elevated in diabetics.
The researchers say greater medical surveillance in the diabetic group might have led to a higher rate of ACS diagnosis. However, they point out, the adjusted hazard ratio "was not substantially changed by incorporating the number of ambulatory visits as a covariate in the analysis."
Subgroup analysis showed higher risks for ACS in all sex and age subgroups. There was no interaction effect between diabetes and either sex or age.
The mechanism underlying the association between diabetes and ACS is still uncertain, but the investigators suggest it "may be explained, at least in part, by a diabetes mellitus-related chronic inflammatory process with increased growth factor expression, which, in turn, leads to joint synovitis and subsequent capsular fibrosis."
The researchers acknowledge that they didn’t have information on lifestyle factors, such as physical activity and obesity which is a drawback of their study. Also, as "most of the inhabitants in Taiwan are of Chinese ethnicity, it is uncertain whether our findings can be extrapolated to other ethnic groups."
But overall, the authors say, there is indeed an increased risk for ACS in diabetics.
"Further studies are required to investigate the underlying pathophysiological mechanism for this positive association between diabetes mellitus and ACS," they conclude.
Online paper in Arthritis Care & Research, Dec 21, 2012