Clinical impact of persistent hyperCKemia in a Norwegian general population: a case-control study

In this case-control study we assessed the clinical impact of persistent hyperCKemia in a Norwegian general population. HyperCKemia was defined according to the NORIP- references (women 35-210 U/L, men <50 years 50-400 U/L, and men ≥50 years 40-280 U/L). We compared the frequency of muscular symptoms and function, neuromuscular diseases and risk factors between 120 cases with persistent hyperCKemia and 130 age- and sex-matched controls with normal CK values, all recruited from the single-centre, population-based prospective Tromsø Study. The participants underwent a standardized interview assessing muscle symptoms, physical activity, use of statins and presence of other CK risk factors, prior to clinical neurological and neurophysiological examination. Knee extensor muscle strength (Cybex NORM dynamometer) and dominant hand grip strength (Martin Vigorimeter) was assessed. A total of 85 cases (71%) reported either muscle pain, muscle stiffness or cramps, compared to 70 controls (54%) (p=0.017) There were no differences in muscle strength between the groups. In men, weight, Body Mass Index and muscle symptoms were significantly higher in the group with persistent hyperCKemia. In women, no differences between the groups were detected. Use of statins was similar in cases and controls. We diagnosed 3 women with previously unknown myopathy, all in the group with persistent hyperCKemia. This study support that CK may be used as a marker of muscular symptoms in the general population.