Table 1. Study on correlation of sun exposure and gastric cancer.

Study design	Study period /Participants	Vitamin D index	Outcome	Summary of findings	References (year, country)
Ecologic study	1970-1994	TOMS DNA-weighted UVB	Mortality of premature gastric cancer	Inverse correlation P < 0.001	Grant et al. (2002, US)
Ecologic study	1961-1990	Average annual hours of solar radiation	Mortality of gastric cancer	Inverse correlation P < 0.001	Mizoue (2004, Japan)
Ecologic study	1993-2002	Latitude and Annual erythemally weighted UVB	Mortality and incidence of gastric cancer	Inverse correlation P < 0.001	Boscoe et al. (2006, US)
Ecologic study	1990-1994	Latitude and dietary supply factors	Mortality and incidence of gastric cancer	Inverse correlation P < 0.05	Grant et al. (2006, western European)
Ecologic study	1970-1994	TOMS DNA-weighted UVB	Mortality of gastric cancer	Inverse correlation P < 0.001	Grant et al. (2006, US)
Ecologic study	1978-1992	Latitude, skin cancer and melanoma	Mortality of gastric cancer	Inverse correlation p < 0.01	Grant et al. (2007, Spain)
Case-control	416,134 cases 3,776,501controls	Skin cancer and sunexposure	Incidence of gastric cancer	Inverse correlation SIR: 0.65 95%CI:0.45–0.91	Tuohimaa et al. (2007, Five Continents)
Ecologic study	1950-1994	TOMS DNA-weighted UVB	Mortality of gastric cancer	Inverse correlation p < 0.001	Grant et al. (2010, US)
Ecologic study	1998–2002	UVB from NASA database and GIS methods	Mortality of gastric cancer	Inverse correlation p < 0.001	Chen et al. (2010, China)
Nested case-control	115,016 cases 987,893controls	Skin cancer	Incidence of gastric cancer	No correlation OR:1.00 95%CI:0.85–1.17	Lindelof et al. (2012, Swedish)
Ecologic study	2000-2002	UVB intensity from NASA database and spatial Kriging method	Mortality of gastric cancer	Inverse correlation HR:0.89 95%CI:0.83-0.95	Chen et al. (2013, China)