A critical appraisal of epidemiological studies comes from basic knowledge: a reader's guide to assess potential for biases

Table 1 Baseline characteristics of head and neck cancer cases and controls according collected variables[12]

Variable	Cases n (%)	Controls n (%)	p value*
*Age groups (years)*			0.168
< 60	35 (28.2)	88 (35.3)
> 60	89 (71.8)	161 (64.7)
Total	124	249
*Gender*			0.123
Male	105 (84.7)	194 (77.9)
Female	19 (15.3)	55 (22.1)
Total	124	249
*Weight ± SD (Kg)*	72.70 ± 12.40	73.09 ± 12.15	0.775†
*Alcohol consumption*			0.001
No alcohol	37 (30.3)	107 (44.8)
1–30 gr/die	53 (43.4)	122 (51)
> 30 gr/die	32 (26.2)	10 (4.2)
Total	122	239
*Fruit intake*			0.197
≤ 1/day	69 (57.0)	153 (76.5)
>1/day	52 (43.0)	86 (23.5)
Total	121	239
*Vegetable intake*			0.678
≤ 1/day	95 (78.5)	183 (76.6)
>1/day	26 (21.5)	56 (23.4)
Total	121	239
*Smoking status*			0.001
Never smokers	17 (14.0)	133 (55.6)
Ever smokers	104 (86.0)	106 (44.4)
Total	121	239
*Physical activity*			0.001
Never	109 (90.8)	172 (72.0)
1–4 times/month	2 (1.7)	43 (18.0)
>4 times/month	9 (7.5)	24 (10.0)
Total	120	239
*Solvents*			0.003
No	115 (95.0)	238 (99.6)
Yes	6 (5.0)	1 (0.4)
Total	121	239
*Paints*			0.004
No	114 (94.2)	238 (99.2)
Yes	7 (5.8)	2 (0.8)
Total	121	240

* χ² test used to test statistically significant differences between groups; † Student's t-test

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