2011-2016

Purpose of the project and any changes in the purpose during the project period

The project's main aim has been to study risk factors for cognitive decline and dementia diseases, with a specific focus on lifestyle (leisure activities) and socioeconomic (education, occupational complexity) factors. The project's main purpose has not changed, but its more specific purposes have been extended to also investigate the influence of marital status and parenthood on dementia and the impact of stress on cognitive function and dementia. The project results have been published in several peer-reviewed international journals.

One change that has occurred is that the project´s available databases needed to be complemented with a few variables to be able to answer some of the planned issues, which have caused a slight delay in the project. Furthermore, military service data has been added for some of the cohorts in the Betula project. This addition has given an opportunity to study the relationship between early cognitive ability, educational and professional complexity, and subsequent cognitive decline and risk of dementia; the results of this research should be published within this year.

The project's three most important results and a discussion of these results

An interesting and important result emerged from our study of the impact of stressful life events in relation to incidental dementia (Sundström et al., 2013). In this project, we used prospective longitudinal data from the Betula Project and a more extensive battery of life event questions than has previously been studied. The questionnaire that participants answered included a total of 55 specific life events where for each life event, the emotional impact and emotional adjustment were asked for. We also wanted to investigate whether the existence of positive life events might act as a buffer against possible adverse effects of negative life events, which to our knowledge have not been studied before, but have been proposed theoretically. However, despite our extensive data on life events, we did not find any significant association between negative life events and later risk of dementia. Nor did we find that positive life events would serve as a buffer for the possible harmful effects of negative events. The results of this study therefore do not support the previous suggested hypothesis that adverse life events trigger the onset of dementia diseases.

Another interesting finding derives from our study on the effects of perceived long-term stress on both subjective and objective aspects of our cognition (Rönnlund et al., 2013). This study also used longitudinal data from the Betula project. Two groups were created; one group consisted of people who reported being generally stressed at both the first and the two follow-up test sessions (5 and 10 years later) and the other group consisted of the same number of people (matched in terms of age and gender) who considered themselves to be low stressed at all three test occasions. These groups were then compared in terms of both subjective and objective measures of cognition. The results showed that the stressed group rated their memory as worse over time as compared to the low-stress group. Moreover, the stressed group also reported more depressive symptoms over time than the control group. However, in contrast to the subjective memory reports, there was no difference in terms of objective cognitive performance over time. These results are interesting and constitute an important contribution to previous research in this area.

The third result to highlight springs from our studies on marital and parental status and the risk of dementia. This has been researched in two studies; the first was based on data from the Betula project and the other on data from the so-called Linnaeus Database, a longitudinal database of the entire Swedish population with data from the National Board of Health and Welfare (data on death causes and hospitalizations) and data from Statistics Sweden (various socioeconomic conditions). In the first study, based on the Betula project, we found a particularly increased risk of dementia in people who were unmarried, especially in those being widowed and without children. In the second study, based on data of the entire Swedish population, we investigated the association between marital status and dementia, while controlling for covariates such as income, and also investigated whether there are differences between early and late onset of dementia. Finally, we also investigate whether there was a gender difference in the association between marital status and dementia. The results showed each non-married subcategory to be associated with a significantly higher risk of dementia than the married group, and this effect persisted even after adjustment for potential confounders, including income and education. In addition, marital status was related to both early-onset and late-onset dementia, but with a slightly higher risk for early-onset dementia. Moreover, all non-married status were associated with dementia for both men and women to a similar degree.

New research questions generated by the project

One of the new research questions arising from the project deals with the effect of subjective loneliness of cognitive function and risk of dementia. The project's available longitudinal database makes it possible to evaluate fully the impact of subjective perceived loneliness over time, while taking into account the effect of social networks (including marital status), stress, and depression. Perceived loneliness has in previous research found to be related to general health problems, and has also been linked to different personality traits. New studies are planned to investigate the role of subjective loneliness for cognitive function, cognitive aging, and dementia, while taking the above factors into account.

Other examples of research questions that the project raises addresses the relationship between family networks in a broader sense on cognitive aging and dementia. To have contact with adult children, grandchildren and siblings may provide social contact and also to some extent compensate for a smaller social network due to divorce or death, and also reduce feeling of loneliness and depression. Studies are planned to study more closely the impact on family networks (adult children, grandchildren or siblings) on cognitive function and dementia. In addition, the impact of geographical proximity between the elderly and their adult children, grandchildren, or siblings on risk of dementia are also planned to be examined.

The project's international presence

The project is internationally anchored to the extent that its performance has been (and will continue to be) published in several international journals, and the project is also based on established international research. Furthermore, some of its results have also been presented and discussed at international research conferences.

Informative research efforts outside the scientific community

The project's research informative activities outside the scientific community have been through presentation at the local national pensioners´ organization and through the Betula project's informational meetings and symposiums. Parts of the project results have also been presented at a research discussion, which was open to the general public. After all articles have been published, more presentations outside the scientific community will hopefully take place.

The project's two main publications and a discussion of these

Since not all works have been published yet, it is a bit difficult to predict which two will be the most important in the end, but at present I estimate these two to be of the greatest likely interest.
Sundström, A., Westerlund, O., Kotyrlo, E. (2016). Marital status and risk of dementia: a nationwide population-based prospective study. BMJ Open, 6, e008565.
Sundström, A., Rönnlund, M., R. Adolfsson and Nilsson, L-G. (2014). Stressful Life Events Are Not Associated with development of dementia. Psychogeriatrics International, 26, 147-154.

The first study above investigates the effect of marital status on dementia, and is the largest such study to date. The study also takes the opportunity to assess the impact of various socio-economic factors, any differences between the genders, and any differences between early- and late-onset dementia. The results showed a significantly increased risk of dementia for all non-married groups for both early- and late-onset dementia, although a slighter higher risk was observed for early-onset dementia. Moreover, the risk of dementia by marital status was also evident for both men and women to a similar degree.

The second study examines stressful life events in a more detailed way than previous studies have done, for example, by considering the individually experienced emotional impact of an event and also by considering both negative and positive events and whether positive life events might act as a buffer against possible adverse effects of negative life events. To our knowledge, this has not been studied before in relation to dementia. The results revealed no association between either negative or positive life events or dementia, hence disproving the hypothesis that stressful life events trigger the onset of dementia.

The project's publishing strategy and comments

The project's publishing strategy is to be published in internationally well-renowned international peer-reviewed journals of relevance to the subject of the article. When it has been possible, the publishing has also been done through open access (two published and one ongoing so far).

Publications

Rönnlund, M., Sundström, A., Eriksson, D., & Nilsson, L-G. (2013). Effects of perceived long-term stress on subjective and objective aspects of memory and cognitive functioning in a middle-aged population-based sample. Journal of Genetic Psychology, Research and Theory on Human Development, 174, 25-41.

Rönnlund, M., Sundström, M., & Pudas, S. (manuscript). Midlife level and 15-year changes in general cognitive ability in a sample of men: The role of education, early adult ability, bmi, and pulse pressure.

Sundström, A., Rönnlund, M., Adolfsson, R., & Nilsson, L-G. (2014). Stressful life events are not associated with development of dementia. International Psychogeriatrics, 26, 147-154.

Sundström, A. Rönnlund, M. (manuscript). Relationship between work complexity and risk of dementia.

Sundström, A., Westerlund, O., Kotyrlo, E. (2016). Marital status and risk of dementia: a nationwide population-based prospective study. BMJ Open, 6, e008565.

Sundström, A., Westerlund, O., Mousavi-Nasab, SM., Adolfsson, R., Nilsson, L-G. (2014). The relationship between Marital and Parental Status and Risk of Dementia. International Psychogeriatrics, 26, 1-9.

Sörman, D. E., Rönnlund, M., Sundström, A., Adolfsson, R., Nilsson, L-G. (2015). Social relationships and risk of dementia: a population-based study. International Psychogeriatrics, 27, 1291-1399.

Sörman, D.E., Rönnlund, M., Sundström, A., Norberg, M. & Nilsson, L-G. (submitted). Social network size and cognitive function in middle-aged adults: Cross-sectional and longitudinal associations. Journal of Adult Development.

Sörman, D. E., Sundström, A., Rönnlund, M., Nilsson, L-G (2014). Leisure activity in old age and risk of dementia. A 15-year prospective study. The journal of Gerontology. Series B, Psychological Science and social sciences, 69, 493-501.

Konferensbidrag

Rönnlund, M., Sundström, M., & Pudas, S. (2015). Interindividual differences in onset of decline in general intelligence in old age: The role of social network size, overweight, and hypertension. ISIR (International Society for Intelligence Research), Albuquerque, New Mexico, 18-20 September.

Sundström, A., Westerlund O., & Kotyrlo, E. (2015). Marital status and risk of dementia: a nationwide population-based prospective study. Society for Longitudinal and Life Course Studies (SLLS) conference, Dublin, 18-21 October.

Sörman, D. E, Rönnlund, M., & Sundström, A. (2012). Leisure-time activity in old age as predictors of impending dementia: A 15-year prospective study. Cognitive Aging Conference, Atlanta, GA, April.