Table 2:

The estimated effect of the CCAA on changes in MMSE score by difference-in-differences models.

	Effect estimate (95% CI), MMSE score	p value
Target ≥ 5%
Model 1	1·36 (0·47–2·25)	0·0032
Model 2	2·38 (1·25–3·50)	<0·0001
Model 3	2·35 (1·22–3·48)	<0·0001
Model 4	2·45 (1·32–3·57)	<0·0001
Target ≥10%*	1·39 (0·52–2·27)	0·0023
Target ≥12%*	1·27 (0·45–2·09)	0·0031
Target ≥15%*	1·07 (0·22–1·92)	0·014

Model 1 is adjusted for inverse probability weighting from baseline and offset of MMSE trend. Model 2 is adjusted for survey month based on model 1. Model 3 is adjusted for marital status, alcohol drinking, smoking, and physical activity based on model 2. Model 4 is based on model 3, but is also adjusted for intake of fruit and vegetables, water quality, living condition, and income source. Effect estimates were also provided using different targets of the annual particulate matter reduction targets (≥10%, ≥12%, and ≥15%). CCAA=China’s Clean Air Act. MMSE=Mini-Mental State Examination.

^*assessed using model 4.