Does chronic disease influence susceptibility to the effects of air pollution on depressive symptoms in China?

Table 1 Statistical description

Variable	All sample (N = 23,268)		Group with chronic disease (N = 15,412)		Group without chronic disease (N = 7856)		Group with chronic disease VS Group without chronic disease
Variable	Mean	Std. Dev.	Mean	Std. Dev.	Mean	Std. Dev.	P-value^a
Air pollution emission intensity (tons per 100 million Chinese yuan)
SO₂	82.950	78.355	82.602	74.980	83.632	84.587	< 0.001
TSP	45.571	49.025	46.510	50.816	43.729	45.253	< 0.001
Air pollution emission per unit area (tons/km²)
SO₂	6.812	8.307	6.667	8.728	7.097	7.403	< 0.001
TSP	3.079	3.495	2.998	3.576	3.236	3.326	< 0.001
Air pollution emission per capita (tons/10,000 people)
SO₂	135.137	120.211	132.127	118.256	141.042	123.753	< 0.001
TSP	70.938	81.064	70.173	80.964	72.440	81.243	< 0.001
Climatic indexes
Average monthly temperature (0.1 °C)	265.990	39.353	266.038	39.678	265.894	38.710	< 0.001
Average monthly relative humidity (%)	73.253	7.603	73.077	7.634	73.599	7.529	< 0.001
Depressive symptoms	11.623	4.664	12.176	4.858	10.538	4.043	< 0.001
Age	60.101	9.989	61.101	9.834	58.139	10.000	< 0.001
Income (Chinese yuan/year)	8175	14,912	7970	13,343	8576	17,583	0.011

	n	%	n	%	n	%	P-value^b
Male	11,108	47.739	7165	46.490	3943	50.191	0.010
Unmarried	2854	12.266	1991	12.919	863	10.985	0.022
Living in urban area	9016	38.748	5947	38.587	3069	39.066	0.730
Education							< 0.001
No education	5973	25.670	4145	26.895	1828	23.269
No education but can read/write	4218	18.128	2946	19.115	1272	16.191
Primary school	5181	22.267	3498	22.696	1683	21.423
Junior high school and above	7896	33.935	4823	31.294	3073	39.117
Employment status							< 0.001
Unemployed	7734	33.239	5623	36.485	2111	26.871
Self-employed	10,162	43.674	6710	43.537	3452	43.941
Wage earner	5372	23.087	3079	19.978	2293	29.188
Insurance							0.037
Uninsured	1455	6.253	854	5.541	601	7.650
NCMS and URBMI	18,635	80.089	12,389	80.385	6246	79.506
UEBMI	3178	13.658	2169	14.074	1009	12.844
Health behavior
Current Smoker	7713	33.149	4757	30.866	2956	37.627	< 0.001
Current Drinker	7756	33.333	4932	32.001	2824	35.947	0.005

^aFrequencies with percentages were presented for categorical variables. P-values were calculated by Chi square test between groups having chronic disease or not
^bMeans with standard deviations were presented for continuous variables, and P-values were calculated one-way ANOVA between groups having chronic disease or not

ISSN: 1752-4458