Correction: Socioeconomic gradient in physical activity: findings from the PERSIAN cohort study - Farid Najafi; Shahin Soltani; Behzad Karami Matin; Ali Kazemi Karyani; Satar Rezaei; Moslem Soofi; Yahya Salimi; Mehdi Moradinazar; Mohammad Hajizadeh; Loghman Barzegar; Yahya Pasdar; Behrooz Hamzeh; et al. (BMC, 2022)