Fruit and Vegetable Intake and the Risk of Chronic Obstructive Pulmonary Disease: A Dose-Response Meta-Analysis of Observational Studies

Table 2

Summary risk estimates of COPD for fruit and vegetable intake by study characteristics.

		No. of studies	Pooled RR	95% CI	I^2 statistic (%)	value for heterogeneity
Fruits plus vegetables
	All studies	8	0.75	0.68–0.84	46.7	0.021
	Study design
	Cohort	4	0.81	0.72–0.92	53.9	0.034
	Cross-sectional	2	0.63	0.48–0.83	54.1	0.088
	Case-control	2	0.59	0.42–0.84	0	0.592
	Continent
	Europe	4	0.69	0.58–0.82	65.4	0.005
	Asia	2	0.75	0.64–0.88	0	0.653
	America	2	0.92	0.77–1.10	0	0.602
	Gender
	Both	4	0.64	0.53–0.77	23.3	0.244
	Male	2	0.78	0.70–0.87	0	0.712
	Female	2	0.84	0.66–1.07	77.7	0.004
	Exposure measure
	FFQ	6	0.79	0.70–0.88	44.1	0.050
	Others	2	0.63	0.48–0.83	54.1	0.088
Fruits
	All studies	8	0.72	0.66–0.79	1.3	0.419
	Study design
	Cohort	4	0.71	0.63–0.79	0	0.419
	Cross-sectional	2	0.65	0.35–1.21	56.8	0.128
	Case-control	2	0.66	0.40–1.11	17.2	0.272
	Continent
	Europe	4	0.67	0.60–0.76	19.6	0.292
	Asia	2	0.80	0.66–0.97	0	0.942
	America	2	0.81	0.63–1.05	0	0.910
	Gender
	Both	4	0.76	0.63–0.91	21.6	0.281
	Male	2	0.73	0.63–0.85	0	0.795
	Female	2	0.70	0.54–0.90	55.9	0.132
	Exposure measure
	FFQ	6	0.70	0.63–0.78	0	0.536
	Others	2	0.65	0.35–1.21	56.8	0.128
Vegetables
	All studies	8	0.76	0.63–0.92	66.7	0.009
	Study design
	Cohort	4	0.90	0.81–1.00	0	0.424
	Cross-sectional	2	0.54	0.36–0.83	56.4	0.130
	Case-control	2	0.54	0.33–0.87	0	0.545
	Continent
	Europe	4	0.70	0.53–0.94	76	0.006
	Asia	2	0.64	0.49–0.85	0	0.899
	America	2	1.03	0.80–1.32	0	0.657
	Gender
	Both	4	0.56	0.45–0.71	0	0.631
	Male	2	0.83	0.71–0.97	0	0.698
	Female	2	0.97	0.84–1.13	0	0.478
	Exposure measure
	FFQ	6	0.88	0.79–0.98	31.6	0.199
	Others	2	0.54	0.36–0.83	56.4	0.130

COPD: chronic obstructive pulmonary disease; RR: relative risk; CI, confidence interval.