Associations of cigarette smoking, betel quid chewing and alcohol consumption with high-sensitivity C-reactive protein in early radiographic knee osteoarthritis: a cross-sectional study

OBJECTIVES: High-sensitivity C-reactive protein (hsCRP) is possibly related to osteoarthritis (OA) progression and a variety of OA-related symptoms. This study aimed to examine associations between cigarette smoking, betel quid chewing and alcohol consumption and hsCRP in early radiographic knee OA. DESIGN: Cross-sectional health examination survey. SETTING: This primary study was conducted in a health examination centre in China. PARTICIPANTS: 936 (656 men and 280 women) patients with early radiographic knee OA were included in this cross-sectional study. PRIMARY AND SECONDARY OUTCOME MEASURES: Smoking status was classified into four levels based on daily smoking habit: 0/day, 1–10/day, 11–20/day and >20/day. Betel quid chewing and alcohol consumption status was divided into ‘Yes’ or ‘No’. Early radiographic knee OA was defined as Kellgren Lawrence (K-L) grade 1 or 2 in at least one leg, and elevated hsCRP was assessed as ≥3.0 mg/L. RESULTS: After adjustment for a number of potential confounding factors, a significant positive association between cigarette smoking and hsCRP was observed in the multivariable model. The multivariable-adjusted ORs (95% CI) of elevated hsCRP (≥3.0 mg/L) in the second (1–10/day, n=133), third (11–20/day, n=59) and highest (>20/day, n=104) cigarette smoking categories were 1.54 (95% CI 0.91 to 2.61), 1.27 (95% CI 0.57 to 2.79) and 2.09 (95% CI 1.20 to 3.64), respectively, compared with the non-smoker category (n=640). In addition, there was a positive dose–response relationship between cigarette smoking and elevated hsCRP (p for trend=0.01). No significant associations between betel quid chewing and alcohol consumption and hsCRP were observed in the multivariable model. CONCLUSIONS: This study indicated that cigarette smoking was positively associated with serum hsCRP level in patients with early radiographic knee OA. However, in view of the nature of cross-sectional designs, the results need to be confirmed by further prospective studies.