Trajectory of metabolic syndrome and its association with knee pain in middle-aged adults

Objective: Metabolic syndrome (MetS) is characterised by the clustering of central obesity with metabolic abnormalities. We aimed to describe the association of MetS and trajectories of MetS over 10-13 years with knee symptoms in general population-based middle-aged adults. Methods: Fasting blood biochemistry, waist circumference and blood pressure measures were collected during Childhood Determinants of Adult Health (CDAH)-1 study (year:2004-6; n = 2447; mean age:31.48 +/- 2.60) and after 10-13 year at CDAH-3 (year:2014-2019; n = 1549; mean age:44 +/- 2.90). Participants were defined as having MetS as per International Diabetes Federation (IDF) definition. Knee symptoms were assessed using Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scale at CDAH-3 (mid-adulthood). Results: The prevalence of MetS increased from 8 % at young adulthood (female:52.06 %) to 13 % in mid-adulthood (female:53.78 %) over 10-13 years. Presence of MetS at mid-adulthood was associated with knee symptoms at mid-adulthood [ratio of means (RoM): 1.33; 95%CI:1.27,1.39]. Four MetS trajectories were identified-'No MetS' (85.01 %); 'Improved MetS' (2.14 %), 'Incident MetS' (8.81 %), and 'Persistent MetS, (4.04 %). Compared to 'No MetS', 'Persistent MetS' [RoM:1.15; 95%CI:1.06,1.25], 'Incident MetS' [RoM:1.56; 95% CI:1.48,1.65], and 'Improved MetS' [RoM:1.22; 95%CI:1.05,1.41] was associated with higher knee symptoms. Notably, 'Incident MetS' was strongly associated with knee symptoms [RoM: 1.56; 95%CI:1.48,1.65] and pain [RoM:1.52; 95%CI:1.37,1.70] at mid-adulthood. Conclusion: In this sample of middle-aged adults, there was a significant positive association between MetS and knee symptoms. Relative to those without MetS at either life stage, the elevation in mean knee pain scores was more pronounced for those who developed MetS after young adulthood than for those who had MetS in young adulthood.