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Mortality in blind subjects. A population-based study on social security files from Baden-Württemberg
H G Krumpaszky1, K Dietz, A Mickler
1Department of Medical Information Processing, University of T ubingen, Germany.hans.krumpaszky@dgn.de
Background:
Previous studies indicated that mortality is increased in blind subjects. However, no detailed analysis with respect to causes of blindness and the effect of additional diseases has been performed. The present study was undertaken to examine these questions.
Materials And Methods:
The investigation is based on social security files from the Württemberg-Hohenzollern region (population 5.5 millions) in Germany. In total, 571 files of blind subjects whose blindness benefits terminated (mostly due to death) in 1994 were included. Medical opinions on ophthalmological status and general health were extracted from the files. Standardised mortality ratios (SMRs) on the basis of life tables of former West Germany were calculated using maximum likelihood methods taking into account censoring.
Results:
Most subjects in our study had one or more additional diseases at onset of blindness (74%). The SMR in all blind is 1.41 [95% CI (confidence interval) = 1.28-1.54; n= 571]. Mortality of blind subjects is increased if subjects suffer from multiple disease at onset of blindness: the SMR in blind with multiple diseases is 1.76 (95% CI = 1.58-1.94; n = 421) versus 0.85 (CI = 0.70-1.0; n = 150) in otherwise healthy blind subjects. In cases where specifically ocular diseases were responsible for the visual loss, the symbol [M] indicates that the blind subject suffered from multiple disease at onset of blindness and [E] denotes that this was not the case. The SMRs for main causes of blindness are: macular degeneration [M] 1.5 (CI = 1.3-1.8; n = 123), [E] 1.1 (CI = 0.8-1.5; n = 43); glaucoma [M] 1.6 (CI = 1.3-2.1; n = 65), [E] 1.0 (CI = 0.6-1.5; n = 26); high myopia [M] 1.2 (CI = 0.8-1.7; n = 32), [E] 0.8 (CI = 0.5-1.2; n = 21); optic atrophy [M] 1.1 (CI = 0. 6-1.8; n = 19), [E] 1.4 (CI = 0.4-3.2; n = 4), and tapetoretinal degeneration [M] 2.3 (CI = 1.1- 4.2; n = 10), [E] 0.9 (CI = 0.4-1.8; n = 12). The SMR of cases of blindness in conjunction with other diseases was fairly high for diabetic retinopathy: 5.5 (CI = 4.4-6. 8; n = 81). Central-nervous-system-triggered blindness led to an SMR of 1.5 (CI = 1.0-2.2; n = 37).
Discussion:
According to the results of the present study mortality is significantly increased in blind subjects. However, increased mortality in cases of blindness due to specifically ocular disease (e.g. macular degeneration) is associated with the presence of multiple (extra-ocular) diseases at onset of blindness.