Underlying cause of death in Danish patients with multiple sclerosis: Results from the Danish Multiple Sclerosis Registry

Abstract

Objectives. To determine the underlying causes of death in a large population based register series of patients with multiple sclerosis. Methods. The Danish Multiple Sclerosis Registry, which contains virtually all diagnosed cases of multiple sclerosis in Denmark who were alive in 1949 plus cases with onset of multiple sclerosis in the period 1949-93, who have been diagnosed and notified by 1 January 1994, was linked with the Danish Registry of Causes of Death, in which ICD codes for causes of death from the death certificate are stored for all Danish citizens. Results. 6068 register cases of multiple sclerosis, who had died in the period 1951-93, were included. Multiple sclerosis was noted on the death certificate as the underlying cause of death in 55.4%; cardiac or vascular diseases in 17.6%; cancers in 8.6%; respiratory or infectious diseases in 5.1%; other natural causes in 9.5%; accident or suicide in 3.8%. The distribution varied with age at death. Standardised mortality ratios (SMRs) were computed on the basis of the 8142 incident cases, who had onset of multiple sclerosis within the period 1951-93; the SMRs for causes of death other than multiple sclerosis were highest for infectious or pulmonary diseases: 2.46 (95% confidence interval (95% CI) 2.04-2.94); suicide: 1.62 (95% CI 1.29-2.01); cardiac or vascular diseases: 1.34 (95% CI 1.22-1.48); accidents 1.34 (95% CI 1.02-1.71); and significantly lower than unity for cancers: 0.79 (95% CI 0.70-0.90), lower for men than for women. Conclusions. More than half of the patients with multiple sclerosis die from multiple sclerosis or complications of the disease. Among other causes, patients with multiple sclerosis have an increased risk of dying from heart or vascular diseases but a reduced risk of dying from cancer. An increased risk of death from suicide and accidents can be indirectly attributed to multiple sclerosis. The diminished risk of dying from cancer may be a result of incomplete ascertainment of cancers in disabled patients with multiple sclerosis.