| 1. |
- Holmgren, Sara, 1974-
(författare)
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Effects of family configuration on cognitive functions and health across the adult life span
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis examines whether childhood family configuration influences performance on cognitive functions and health in adulthood and old age. All studies examined participants in the Betula Prospective Cohort Study aged 35 to 85 years (Nilsson et al., 1997). Study Ι established whether there are reliable effects of sibship size and birth order in a large sample of participants in adulthood and old age. The results showed that the effects previously demonstrated in children and adolescents (e.g., Belmont & Marolla, 1973; Mercy & Steelman, 1982) have a long-lasting effect and can be demonstrated in an adult sample. These studies concluded that intelligence and executive functioning decreased as the sibship size increased. Birth order, in contrast, had only influenced executive functions and working memory: earlier born siblings performed at a higher level than later born siblings. Study ΙΙ examined whether the effects of sibship size and birth order can be replicated and extended to episodic memory and whether the effects of family configuration are stable over a five-year interval. The results showed that early born siblings and siblings belonging to a smaller sibship size performed at a higher level and that these effects on both recall and recognition were stable over a five-year interval. Study ΙΙΙ explored whether childhood family configuration influences chronic adult diseases (myocardial infarction and circulatory disorders, stroke, and hypertension). The overall results showed that being born in a large sibship is a risk factor for stroke, myocardial infarction /circulatory disorders, and hypertension in old age. The results also suggest that being born early in a sibship is a predictor of stroke.
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| 2. |
- Holmström, Stefan, 1970-
(författare)
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Workplace stress measured by Job Stress Survey and relationships to musculoskeletal complaints
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main purpose of this thesis was to evaluate and test the Job Stress Survey (JSS, Spielberger, 1991; Spielberger & Vagg, 1999), a self-report instrument which assesses workplace stress. In the thesis a thorough evaluation is made of JSS scales and items, and the relations to health, particularly musculoskeletal complaints. The aim of Study I was to evaluate the factor structure and the psychometric properties of a Swedish version of the JSS. The instrument was distributed to medical service personal and metal industry workers (n=1186). Factor analyses demonstrated a good resemblance between the present version and the American original version. The results also showed that the internal consistencies, as well as the test-retest reliabilities of the scales are high, and the concurrent validity are good. Study II examined work-related stress measured by JSS for the subgroups of gender, industry workers and medical service personnel, and special attention was given to the problem of differential item functioning (DIF) on these subgroups. The main findings were that both gender and occupation has a substantial impact on specific sources of work-related stress assessed by JSS scales and individual items. The result of the DIF analyses showed no item bias in the gender subgroup, but for the occupational subgroups there where items showing DIF in two of the scales. These items do not jeopardize the conclusions made on scale level since the number of items showing DIF are too few to make an impact on the overall result on the different scales. In Study III the relation between self-reported stress and health, particularly musculoskeletal problems were examined longitudinally in two metal industry factories. Results showed high levels of stress and musculoskeletal complaints in these factories and significant and strong relationships between the JSS scales and musculoskeletal, as well as psychosocial ratings. Lack of Organizational Support was found to be more related to musculoskeletal pain than Job Pressure. Longitudinal differences were found between the factories and between different types of musculoskeletal complaints. The general conclusions from the studies are that the present version of JSS shows a good resemblance with the American original, and that JSS is a useful instrument for studying relationships between stress and health.
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| 3. |
- Söderfjell, Stefan, 1970-
(författare)
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Musculoskeletal pain, memory, and aging : Cross-sectional and longitudinal findings
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The general aim of the thesis was to investigate potential differences in memory performance between participants across the adult life span with and without self-reported musculoskeletal pain. Chronic musculoskeletal pain is a major health related problem in our society. A common complaint related to chronic pain is about cognitive difficulties in attention, memory, and decision making. A number of studies have demonstrated that people with pain also perform wors on tasks measuring, for example episodic memory, semantic memory, and working memory. The present thesis aimed at replying these findings, by using a non-clinical population based sample. the potential differences in memory performance between people with and without pain were examined across the adult life span, in order to disentangle potential pain by age interactions. This was made by using both cross-sectional and longitudinal data. Study I aimed at studying differences in episodic memory performance, semantic memory performance, and implicit memory performance, between people with and without musculoskeletal pain. Differences were found for all three memory systems, but disappeared after controlling for years of formal education. In Study II an extension of the first study was made, in which performance on a range of cognitive tests were analysed. General differences were demonstrated , but yet again, years of education together with depression ruled out the effects. The most robust effects were found for word comprehension and construction ability. Finally, Study III used 5- and 10 year follow up studies to examine change over time in cognitive performance as a function of pain. The main finding from this study was that semantic memory for the oldest is impaired over time as a function of pain. An additional analysis showed similar patterns, regardless of age, for construction ability.
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| 4. |
- Jansson, Magnus
(författare)
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On performance analysis of subspace methods in system identification and sensor array processing
- 1995
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis addresses the issue of performance analysis of subspace-based parameter estimation methods in two different applications, namely system identification and sensor array processing. The objective is to study the quality of the estimated models as the amount of data increases, and to suggest improvements and give user guidelines. First, state-space subspace system identification (4SID) methods are formulated in a linear regression framework. This allows us to analyze the problem in a more traditional way. One advantage is that this explains more clearly the effect of the partition of the data in past and future, which is done in 4SID. Also this formulation is useful to relate and compare different proposed approaches to 4SID. The problem of estimating the poles of dynamical systems is considered. In particular, the statistical asymptotic distributions of the parameter estimates of two different 4SID pole estimation methods are studied. The first method is common in 4SID and makes use of the shift invariance structure of the observability matrix, while the second method is a recently proposed weighted least-squares method. From these results the choice of user-specified parameters is discussed, and it is shown that this choice indeed may not be obvious for the shift invariance method. A simple example is provided to illustrate the problem. However, this problem can be mitigated using more of the system structure. It is also shown that a proposed row weighting matrix in the subspace estimation step does not affect the asymptotic properties of the pole estimates. In the second part focusing on sensor array signal processing, parameter estimation from sparse linear arrays is addressed. An algorithm based on the Expectation-Maximization approach is derived. This is an iterative algorithm for solving maximum likelihood problems. In our application a powerful method for uniform linear arrays is used in the maximization step. The use of preprocessing of the covariance matrix before applying a direction of arrival estimation algorithm is also considered. In particular, linear preprocessing of covariance data in conjunction with weighted subspace fitting is analyzed and the asymptotic distribution of the parameter estimates is derived. Some possible applications when the preprocessing and the analysis may be useful are also given.
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