Visual impairment and cancer: a population-based cohort study in Finland

Objectives: To describe the cancer risk pattern of Finnish persons with visual impairment. Methods: A cohort of 17,557 persons identified from the Finnish Register of Visual Impairment was followed-up for cancer through the Finnish Cancer Registry from 1983-95. The degree of visual impairment ranged from moderate low Vision with visual acuity less than 0.3, to total blindness with no perception of light. The standardized incidence ratios (SIR) and 95% confidence intervals (CI) were calculated by primary site; the expected rates were based on national cancer incidence rates. Results: The SIR for overall cancer among totally blind men was 2.2 (CI = 1.3-3.5) while in the entire cohort the incidence was increased by only 15% (1,255 cancers observed cf 1,093 expected). Excesses were observed in both genders in cancers of the liver (SIR = 1.8, CI = 1.2-2.5) and lung (SIR = 1.5, CI = 1.3-1.7); in females in cancers of the stomach (SIR = 1.5, CI = 1.2-1.9) and the colorectum (SIR = 1.3, CI = 1.1-1.6); and in males in cancers of the kidney (SIR = 1.8, CI = 1.1-2.6) and the eye (5.8, CI = 1.9-13). The excess in lung cancer was entirely attributable to age-related macular degeneration (which is most common among smokers). Conclusions: Cancer incidence among the visually impaired tended to be increased for most cancer types. Attention should be paid to lifestyle factors underlying the observed risk increases, such as unbalanced diet.