Body-Mass Index and Mortality in Incident Dementia: A Cohort Study on 11,398 Patients From SveDem, the Swedish Dementia Registry

Abstract

BackgroundBody mass index (BMI) is used worldwide as an indirect measure of nutritional status and has been shown to be associated with mortality. Controversy exists over the cut points associated with lowest mortality, particularly in older populations. In patients suffering from dementia, information on BMI and mortality could improve decisions about patient care. ObjectivesThe objective was to explore the association between BMI and mortality risk in an incident dementia cohort. DesignCohort study based on SveDem, the Swedish Quality Dementia Registry; 2008–2011. SettingSpecialist memory clinics, Sweden. ParticipantsA total of 11,398 patients with incident dementia with data on BMI (28,190 person-years at risk for death). Main outcome measuresHazard ratios and 95% confidence intervals for mortality associated with BMI were calculated, controlling for age, sex, dementia type, results from Mini-Mental State Examination, and number of medications. BMI categories and linear splines were used. ResultsHigher BMI was associated with decreased mortality risk, with all higher BMI categories showing reduced risk relative to patients with BMI of 18.5 to 22.9 kg/m2, whereas underweight patients (BMI <18.5 kg/m2) displayed excess risk. When explored as splines, increasing BMI was associated with decreased mortality risk up to BMI of 30.0 kg/m2. Each point increase in BMI resulted in an 11% mortality risk reduction in patients with BMI less than 22.0 kg/m2, 5% reduction when BMI was 22.0 to 24.9 kg/m2, and 3% risk reduction among overweight patients. Results were not significant in the obese weight range. Separate examination by sex revealed a reduction in mortality with increased BMI up to BMI 29.9 kg/m2 for men and 24.9 kg/m2 for women. ConclusionHigher BMI at the time of dementia diagnosis was associated with a reduction in mortality risk up to and including the overweight category for the whole cohort and for men, and up to the normal weight category for women.