This study, based on a large, geographically diverse, national sample of an older population (60 + years), investigated the importance of life weariness and suicidal thoughts for mortality when controlling for expected age-related factors. A total of 12.5% of participants reported life weariness and suicidal thoughts at baseline. About half of the individuals died and the interactions of higher age and sex increased the risk of mortality. Our analysis has added value concerning our understanding of the effect of life weariness and suicidal thoughts on mortality in older adults. For example, being an individual with life weariness and suicidal thoughts was independently associated with a 1.44 times higher risk (hazard ratio) for mortality at follow-up after 17 years, in comparison with those without such thoughts. Individuals with life weariness and suicidal thoughts had a shorter survival time (2.7 years) and their survival rate was half that of those of other individuals (24.5% vs. 50.6%).
People of advanced age have previously been found to be particularly vulnerable to health problems due to reduced internal and external resources (21), factors also included in the present study. Such conditions increase the complexity of meeting, identifying, treating, and studying older individuals regarding their suicidality; the high mortality rate found in this study underscores the importance of delaying the onset of life weariness and suicidal thoughts in the older population. Furthermore, the findings indicate that subtle and early signs of suicidality, such as life weariness and suicidal thoughts, need to be assessed more structurally and thoroughly in old age, especially within community and primary care settings. By detecting life weariness and suicidal thoughts through screening, identifying causes, and developing solutions, we could improve preventive strategies and treatment, and thereby reduce the risk of premature mortality.
With the expected increase of life weariness and suicidal thoughts in the population due to increased demographic aging, it is vital to understand early signs and risk factors for premature death. The present study contributes to the understanding of the possible long-term importance of demographic and social characteristics on mortality in old age. Our study is supported by earlier evidence about the elevated risk of mortality in older individuals with suicidal thoughts (14, 15). A recent Korean literature review points out the importance of considering multi-level factors, including individual, family, and social aspects, that interact over a lifetime in the protection against suicidal thoughts in old age (22). This highlights the importance of including several factors over time in research. However, there are still few robust studies from other countries and under other conditions, making it difficult to validate results.
Regarding the demographic factors, the present study confirms a number of factors established by previous research, most of which was cross-sectional, regarding the sex and age interaction with suicidality. In this study, more females (8%) than males (3.7%) had life weariness and suicidal thoughts at baseline (P < 0.001). The highest proportion of life weariness and suicidal thoughts was found in the group of females 80 + years (23.0%), followed by the oldest males (17.9%). The results are supported by Barnow et al. (23) and Barnow and Linden (1), but not by Alaneida et al. (24) and Ko et al (25), who found a higher proportion among men. Interestingly, when investigating the predictive value of the sex-age interaction on mortality, we found that males 80 + years with life weariness and suicidal thoughts, not females, had the highest multi-adjusted hazard ratio of mortality (22.4, CI 13.85–36.18). In previous literature, there is no clear consensus on if the sex of older adults has a potential relationship with suicidality. For instance, it has been found that older men are at higher risk of suicide than women (3, 24, 26–29), but also that there are no sex differences as regards suicidal thoughts (12, 30, 31). Here, the varying results may be due to the use of different spectrums of the concept, the contexts, and the measurements of suicidality in the studies of the older population, as well as the age populations included. This complexity justifies the assumption of moderation through several factors, and confirms the relevance of including socio-demographic factors to verify factors contributing to mortality.
Another important finding of the present study was that life weariness and suicidal thoughts increased with higher age. This finding is in agreement with prior research showing that suicidal thoughts increase with advanced age (10), although no previous study used a combined variable encompassing both sex and age. In addition, the highest difference in survival rate was found in males 70–79 years, where those without life weariness and suicidal thoughts had 3.6 years longer survival time (10.9 years vs. 7.3 years, P value < 0.001) than males with life weariness and suicidal thoughts. We did not specifically investigate the risk of death by completed suicide, which is higher in older males, but our study indicates that being a man, especially of high age, with suicidal thoughts, poses a risk for mortality. It should be noted that our study, like previous research, only asked about legal sex (i.e., male or female) and we lack an understanding of how gender identification potentially affects the results presented here.
Several other independent predictors, aside from life weariness and suicidal thoughts and sex-age interactions, had varying yet significant importance for mortality in the models separated for individuals with and without life weariness and suicidal thoughts (cf. Table 3). Therefore, living in a residential care facility, being born in a country outside Europe, not being married, having insufficient financial resources, having low education, and having an insufficient social network should also be factors considered in the discussion of mortality and life weariness and suicidal thoughts in the older population. Although not investigated here, it may not be living in a residential care facility that increase the risk of mortality, but declined physical and mental health and functional ability and a lack of social relationships, which are more common in people living in residential care facilities than in ordinary homes. Holt-Lunstad et al. (32) and Yasuda et al. (33) found the importance of social network contacts for mortality, but also found that contacts decreased with age. Not only a lack of social interactions, but also the number of people that a person feels they can trust, have in previous literature been associated with mortality in old age (34, 35). In Sweden, about half of the older population (80+) are living alone (36). Furthermore, in the age group (80+), more women than men are living alone and about 80% of them are widows (37), often living with restricted financial resources and having low education, i.e., factors connected to mortality in old age (38). Such circumstances need to be considered in the understanding of differences in survival in old age, as well as the varying importance of these factors in the groups with or without life weariness and suicidal thoughts.
In the literature, there are conflicting results regarding whether the effect of suicidal thoughts on mortality in older adults remains after controlling for factors such as depression (15). The findings in the present study suggest that life weariness and suicidal thoughts have an effect on mortality in old age, after controlling for depression. This is in line with two other longitudinal studies which found that suicidal thoughts had a significant association with mortality after controlling for various factors, including depression (14, 15). This finding has important implications for targeting preventive actions for old age mental health and premature mortality. A systematic literature review focusing on preventive interventions for suicidal thoughts in older individuals found that most studies have targeted depression as a risk predictor, for example through primary care depression screening and management (39). Such interventions are important, but may not be sufficient to prevent suicidal thoughts and premature death, in the long term. Furthermore, previous research has found depression to be a strong influential factor for suicidality in old age (see for example (24, 28, 40). Death by suicide was not investigated in the present study, yet our results showed that depression had an effect on mortality in the case of individuals reporting life weariness and suicidal thoughts. Undoubtedly, the effect of life weariness, suicidal thoughts, and depression on mortality is complex, with difficulties determining the potential reverse effects regarding depression and suicidal thoughts on mortality. Still, considering the elevated risk of mortality in individuals with life weariness and suicidal thoughts and without depression in the present study, more research into preventive interventions is needed.
The strengths of this study include the prospective design, with the possibility to investigate the long-term effects on mortality in a large sample, and the nationally representative sample. The study also includes several demographic and social confounders which are relevant in advanced age and can be expected to influence the association between suicidal thoughts and mortality. Furthermore, the sample includes individuals living in urban and rural areas, in ordinary homes and in residential care facilities, meaning that the result can be discussed and generalised in the general old-age population. Limitations might include that we have no information about the individuals who participated at baseline, but were lost at the time of the follow-up. Also, the choice of using self-reported life weariness and suicidal thoughts may introduce a bias by underreporting, due to normalisation and unrecognition (3) of the symptoms in late life. This may lead to a misclassification of the risk group. Moreover, although the item taken from the MADRS scale comprises response alternatives ranging from life weariness to explicit plans and active preparation for suicide, the original item used is described only as suicidal thoughts by the authors (13), which could be misleading in the conceptualisation of the concept (cf. (12).
Among the individuals randomly invited to participate in SNAC, the most common reason not to participate was poor health. It might be a limitation that only depression was included in the analysis as a well-known predictor for suicidal thoughts. There is reason to believe that diseases other than depression may also have a relationship to life weariness and suicidal thoughts and would be relevant to include, especially considering that the variable residential home facility was an independent risk factor for mortality. However, the potential importance of health factors for mortality was outside the scope in the present study. Approximately 3% (n = 203) of the included individuals declined to share information about life weariness and suicidal thoughts, meaning that the rate of individuals with life weariness and suicidal thoughts could be underrepresented. However, the proportion found (12.5%) replicates previous findings of suicidal expressions, where about 13% experienced life weariness (41).