Table 1.

Description of the quality criteria used to assess the quality of the studies.

Quality categories	High quality	Moderate quality	Low quality
Type of study	Longitudinal	Longitudinal	Cross-sectional
Type of parameters used	Only objective parameters with standard definition	Objective parameters with standard definition and self-perceived symptoms	Only self-perceived symptoms or no parameter assessed
Type of data collection	Data collected 3 or more times over the period taken into account	Data collected just two times over the period taken into account	Data collected in a single interview or questionnaire or not collected at all