Exclusive cigar smoking in the United States and smoking-related diseases: A systematic review

Table 5 Meta-analysis results for lung cancer, chronic obstructive pulmonary disease, ischaemic heart disease, stroke and circulatory disease for cigar smoking¹

Disease	Exposure	Number of studies	Relative risk (95%CI) fixed effect	Relative risk (95%CI) random effects	Heterogeneity I2(2)
Lung cancer	Current cigar smokers, excluding KAISER	5	3.36 (2.93 to 3.84)	3.12 (2.11 to 4.62)	85.22 (P < 0.001)
	Current cigar smokers, including KAISER	6	3.29 (2.88 to 3.76)	2.98 (2.08 to 4.26)	82.65 (P < 0.001)
	Former cigar smokers	4	1.61 (1.23 to 2.09)	1.61 (1.23 to 2.09)	0.00 (NS)
	Ever cigar smokers, excluding MALHOT	9	2.35 (2.04 to 2.71)	2.11 (1.64 to 2.72)	54.77 (P < 0.05)
	Ever cigar smokers, including MALHOT	10	2.43 (2.13 to 2.75)	2.22 (1.79 to 2.74)	51.51 (P < 0.05)
COPD	Current cigar smokers, excluding KAISER	3	1.42 (1.02 to 1.96)	1.42 (0.89 to 2.26)	29.95 (NS)
	Current cigar smokers, including KAISER	4	1.44 (1.16 to 1.77)	1.44 (1.16 to 1.77)	0.00 (NS)
	Former cigar smokers	2	1.06 (0.34 to 3.31)	0.47 (0.02 to 9.88)	58.19 (NS)
	Ever cigar smokers	2	0.86 (0.48 to 1.54)	0.86 (0.48 to 1.54)	0.00 (NS)
IHD	Current cigar smokers, excluding NHIS and KAISER	4	1.08 (1.04 to 1.13)	1.08 (1.04 to 1.13)	0.28 (NS)
	Current cigar smokers, including NHIS and KAISER	6	1.09 (1.06 to 1.14)	1.11 (1.04 to 1.19)	48.68 (P < 0.1)
	Former cigar smokers, excluding NHIS	2	1.25 (1.14 to 1.38)	1.23 (0.94 to 1.61)	87.72 (P < 0.01)
	Former cigar smokers, including NHIS	3	1.26 (1.16 to 1.38)	1.26 (1.03 to 1.53)	75.96 (P < 0.05)
	Ever cigar smokers, excluding NHIS	3	1.15 (1.09 to 1.21)	1.16 (1.06 to 1.26)	51.96 (NS)
	Ever cigar smokers, including NHIS	4	1.15 (1.09 to 1.21)	1.15 (1.08 to 1.23)	27.95 (NS)
Stroke	Current cigar smokers, excluding KAISER	4	1.00 (0.93 to 1.08)	1.01 (0.87 to 1.16)	46.09 (NS)
	Current cigar smokers, including KAISER	5	1.01 (0.94 to 1.09)	1.02 (0.92 to 1.13)	33.51 (NS)
	Former cigar smokers	3	1.08 (0.85 to 1.38)	1.08 (0.85 to 1.38)	0.00 (NS)
	Ever cigar smokers	4	1.12 (0.98 to 1.27)	1.11 (0.95 to 1.31)	21.80 (NS)
Circulatory disease	Current cigar smokers, excluding NHIS and NLMS	1	1.10 (1.05 to 1.16)	-	-
	Current cigar smokers, including NHIS and NLMS	3	1.10 (1.05 to 1.16)	1.10 (1.05 to 1.16)	0.00 (NS)
	Former cigar smokers, excluding NHIS and NLMS	1	1.37 (1.24 to 1.52)	-	-
	Former cigar smokers, including NHIS and NLMS	3	1.28 (1.17 to 1.39)	1.11 (0.84 to 1.46)	81.92 (P < 0.01)
	Ever cigar smokers, excluding NHIS and NLMS	2	1.17 (1.11 to 1.23)	1.19 (1.06 to 1.33)	72.63 (P < 0.1)
	Ever cigar smokers, including NHIS and NLMS	4	1.15 (1.10 to 1.21)	1.15 (1.06 to 1.26)	51.29 (NS)

¹Compared with never smoking any tobacco product.

²Heterogeneity between the results included in the meta-analysis, given as the I² statistic together with its significance coded as: Not significant; P < 0.1; P < 0.05; P < 0.01; P < 0.001. The I² statistic is calculated as 100 × (H-df)/H, where H is the heterogeneity chi-squared statistic, df is the degrees of freedom, and if the resulting value is negative I² is taken to be 0. NS: Not significant; COPD: Chronic obstructive pulmonary disease; IHD: Ischaemic heart disease.