Lower total cholesterol and triglyceride levels in ankylosing spondylitis than non-inflammatory rheumatic disease controls in a 1978-98 study: a potential effect of increased physical energetics in manual occupations in the pre-2000 chronologic era.

Objectives: No article on serum lipids in ankylosing spondylitis (AS) and control subjects has been reported from USA. The primary aim of this study was to determine if any difference occurred in serum lipid levels in AS and control rheumatic disorders in two time periods, 1978-98 and 2000-10. The secondary aim was to investigate variables associated with lipid levels and if a difference was found between AS and control disorders.

Methods: The AS patients were compared to non-inflammatory rheumatic disorders (NIRDs) in 1978-98 and 2000-10 surveys and to rheumatoid arthritis (RA) in the 2000-10 survey. Patients were matched within 5 years of age, sex, and clinic or hospital source.

Results: In the 1978-98 survey, entry mean (SEM) serum cholesterol level [mg/dL] was highly (p<0.001) significantly lower in 69 AS [179.0 (4.8)] than 69 matched NIRD controls [208.0 (5.6)]. In 29 pairs of AS and NIRD subjects having manual labour occupations, mean (SEM) cholesterol level was additionally lower in AS [156.7 (5.9)] and higher in 29 NIRD controls [213.3 (8.6)] (p<0.001). In manual labour workers, mean (SEM) serum triglyceride was significantly lower (p=0.004) in 15 AS [110.3 (14.1)] than 14 NIRD controls [185.2 (19.3)]. In the 2000-10 survey, no lipid difference was found between AS vs. NIRD control patients.

Conclusions: In the 1978-98 survey, AS had significantly lower mean serum cholesterol and triglyceride levels than NIRD control patients. Associated manual labour occupations may have significantly contributed to results, possibly related to increased energy expenditures from physical activity in the pre-2000 era.