Spousal bereavement, mortality and risk of negative health outcomes among older adults: a population-based study

Lucas Morin; Jonas W Wastesson; Stefan Fors; Neda Agahi; Kristina Johnell

We used conditional fixed-effect Poisson regression models to compare the incidence rate of non-fatal events during the pre-bereavement and post-bereavement periods with the incidence rate during the reference period (18 to 12 months before spousal loss). For each hazard period, person-time was calculated from the beginning of the interval until either the first event of interest, the date of death or emigration, or the end of the interval. We computed relative incidence ratios (RIR) for each outcome by entering a bereavement-by-time interaction term in the model. 42 This was done to account for the fact that incidence rates during pre-bereavement periods are conditional on survival until the date of spousal loss and, thus, that the observed incidence rates after that date may partly stem from lefttruncation bias. Relative incidence ratios can be interpreted as the relative increase in the risk of experiencing adverse health outcomes among bereaved cases compared with the increase among married controls. This analytical strategy presents the advantage of eliminating the influence of timeinvariant confounders while also removing the effect of time trends in the events. 43 We obtained 95% confidence intervals (CIs) by using robust standard errors to account for clustering within individuals.