This study explored how the structural aspects of a social network (that is, number of social ties, frequency of contact, as well as social participation), along with the functional aspect (social support), relate to mental health. Using data from the baseline questionnaire for the tracking cohort of participants in the Canadian Longitudinal Study on Aging, community-dwelling older adults aged 65-85 years old were studied. Cluster analysis was used to group individuals into different clusters, based on their structural social network characteristics. Six clusters were found, ranging from most socially integrated, to moderately integrated, to socially isolated. Univariate analyses indicated that as level of social integration decreased, individuals fared increasingly worse in terms of their mental health outcomes. Furthermore, a series of mediation analyses showed that social support mediated the relationship between social integration level, and mental health, an effect that was strongest for the most socially isolated individuals. / May 2016

Objectives: Our goal was to explore the association between vision with cognitive change scores and incident depression. Methods: A 3-year prospective cohort study was performed. Incident depression was defined using a cut-off score of 10 on the Center for Epidemiologic Studies Depression scale. Cognitive change was examined by calculating the difference between baseline and follow-up cognitive tests scores. Multivariable Poisson and linear regression were used. Results: Cataract was associated with incident depression (relative risk=1.20, 95% confidence interval 1.05, 1.37). Visual impairment was associated with the 3-year change in Rey Auditory Verbal Learning Test (RAVLT) (β=-0.18, 95% CI= -0.28, -0.07), RAVLT-Delayed (β=-0.13, 95% CI= -0.25, -0.02), and Animal Naming Test (β=-0.95, 95% CI= -1.44, -0.45) scores. Glaucoma was associated with 3-year Mental Alternation Test change scores (β=-0.40, 95% CI -0.77, -0.04). Conclusions: Cataract was associated with increased depression risk. VI and glaucoma are associated with 3-year changes in cognitive test scores.

Background: The COVID-19 pandemic disrupted access to healthcare services in Canada, but little is known about the magnitude of unmet healthcare needs and characteristics associated with increased risk of unmet needs in the adult population. Objectives: First, to describe unmet healthcare needs, including COVID-19 testing access, and to evaluate the association of the social determinants of health (SDOH) and chronic conditions with unmet healthcare needs. Secondly, to evaluate the association between symptoms of depression and anxiety with unmet healthcare needs, and test if the interaction was modified by sex. Methods: The data of 23,972 adults who completed the Canadian Longitudinal Study on Aging COVID-19 Questionnaire Study exit survey (Sept.–Dec. 2020) was analyzed. Three outcomes were evaluated: 1) challenges accessing healthcare, 2) not going to a hospital or seeing a doctor when needed, 3) experiencing barriers to COVID-19 testing. For objective 1, a prospective cohort study was conducted. For objective 2, a cross-sectional study was conducted. RESULTS: Overall, 25% of adults in Canada reported challenges accessing healthcare, 8% did not go to a hospital or see a doctor when needed, and 4% experienced barriers to COVID-19 testing. Several SDOH, including sex, immigrant status, racial background, education and income, were associated with unmet needs. The odds of reporting all three outcomes declined with age. Pre-pandemic unmet needs were strongly associated with higher odds of all three outcomes, while the presence of chronic conditions was associated with higher odds of the first two outcomes. Symptoms of depression and anxiety were strongly associated with all three outcomes. Interaction with sex was found for the first outcome, with stronger associations in females. Conclusions: This thesis identified groups that experienced difficulties accessing healthcare services during the pandemic. Future research may assess consequences of unmet needs, evaluate mechanisms that cause unmet needs and determine ideal interventions. / Thesis / Master of Public Health (MPH) / The COVID-19 pandemic in Canada affected how individuals were able to access healthcare services. To understand which groups experienced a greater level of difficulties, we examined the experience of unmet healthcare needs during the first year of the pandemic using a sample of 23,972 adults that had completed the Canadian Longitudinal Study on Aging (CLSA) COVID-19 Questionnaire Study (Sept. – Dec. 2020). We found evidence that the experience of unmet healthcare needs varied by several sociodemographic characteristics, such as sex, immigrant status, racial background, education and income. Younger adults were more likely to report unmet needs. Individuals with chronic conditions and those had reported unmet healthcare needs prior to the pandemic were also more likely to report unmet needs during the pandemic. Individuals with symptoms of depression and anxiety were also more likely to report unmet healthcare needs. These results can be used to inform interventions that improve access to healthcare services for vulnerable groups.

Objectives: Sarcopenia is defined using a variety of different muscle variables, muscle mass adjustment techniques and cut offs for each variable. The objectives of this thesis were to assess how operational differences in sarcopenia definitions impact the agreement between definitions and the association between sarcopenia and health outcomes such as falls. Methods: A list of sarcopenia definitions was developed which captured the combinations of muscle variables, muscle mass adjustment techniques, and cut offs used in the literature based on a systematic review conducted for this thesis. These definitions were applied to participants taking part in the Canadian Longitudinal Study on Aging, a national study of participants aged 45 to 85 years at baseline. The agreement between the definitions and the association of each definition with falls was assessed. Findings: Both the combination of muscle variables as well as the different muscle mass adjustment techniques generally had limited agreement. Sarcopenia definitions including muscle mass and muscle strength were associated with falls in males, but none of the sarcopenia definitions were associated with falls in females. Area under the curve analyses revealed that even sarcopenia definitions associated with more than two times the odds of falling in males, had a small impact on identifying fallers with values ≤0.56. Conclusions: The results of this thesis show that the existing range of definitions used to define sarcopenia are not equivalent based on the limited agreement and inconsistent association of sarcopenia with falls. The results also show that sarcopenia may have limitations as clinically useful diagnosis for identifying fallers with area under the curve values for all definitions showing that the identification of fallers based on sarcopenic status was at best, modestly better than chance alone. / Thesis / Doctor of Philosophy (PhD) / Definitions for sarcopenia differ in terms of which muscle variables are included, how muscle mass is adjusted, and which cut offs to use for each variables. This thesis assessed the impact of different methods of operationalizing sarcopenia on the proportion of sarcopenic participants, agreement between definitions, and the strength of the association between sarcopenia and falls. The variables used to operationalize sarcopenia as well as different techniques for adjusting muscle mass resulted in poor agreement between definitions. In males, these factors impacted which definitions were significantly associated with falls, and in females, sarcopenia was not associated with falls for any definition. For all definitions, sarcopenia status poorly discriminated between those that would or would not fall. Together, these results show that different sarcopenia definitions are not equivalent and that a standard definition is required. However, this thesis also shows that more work is required to determine the clinical utility of sarcopenia.

Thèse de doctorat présentée en vue de l'obtention du doctorat en psychologie (Ph.D). / Trente à 50% du risque de développer une démence est attribuable à des facteurs modifiables telles l’inactivité physique, l’hypertension et la dépression. Depuis quelques années, certains auteurs considèrent que les troubles du sommeil devraient également être inclus. Notamment, l’apnée obstructive du sommeil (AOS) serait associée à un plus grand risque de déclin cognitif et de démence selon des études épidémiologiques. Toutefois, d’autres études n’ont pas observé ce lien entre l’AOS et le déclin cognitif. Notre équipe a ainsi émis l’hypothèse que certains facteurs modulent l’association entre l’AOS et le déclin cognitif, expliquant une partie de l’hétérogénéité des résultats des études précédentes. Cette thèse vise à caractériser le rôle de l’âge, du sexe et de l’inflammation systémique dans l’association entre le risque d’AOS et la performance cognitive chez les adultes d’âge moyen et les personnes âgées. Afin d’y parvenir, nous avons utilisé le score obtenu à des variantes du questionnaire STOP afin d’établir le risque de présenter de l’AOS, une batterie de tests neuropsychologiques et le dosage de la protéine C-Réactive (CRP) dans le sang dans une grande cohorte canadienne. Ce protocole a mené à une revue narrative et à trois articles de recherche. Le premier article a permis de brosser un portrait actuel des adultes d’âge moyen et des personnes âgées à haut risque d’AOS. Plus spécifiquement, 17,5% des participants de la cohorte (21,9% chez les hommes et 13,1% chez les femmes) ont été identifiés comme étant à haut risque d’AOS. Dans cette étude, les facteurs de risque de présenter un haut risque d’AOS étaient l’âge (55 ans et plus), le sexe masculin, la ménopause, l’obésité, les maladies cardiovasculaires, le diabète, les maladies cérébrovasculaires, les symptômes anxiodépressifs et les niveaux élevés d’inflammation systémique. Dans le deuxième article, nous avons caractérisé les associations entre le risque d’AOS et la performance cognitive selon l’âge et le sexe. Nous avons montré que les femmes à haut risque d’AOS âgées entre 45 et 69 ans ont des performances cognitives plus faibles que celles à bas risque d’AOS, précisément dans les domaines de la mémoire épisodique et des fonctions exécutives. Nous n’avons identifié aucune association entre l’AOS et la performance cognitive chez les hommes. De plus, nous avons observé que l’inflammation systémique médie certaines associations entre le risque d’AOS et les fonctions exécutives chez les hommes et les femmes âgées de moins de 70 ans. Dans le troisième article, nous avons observé que l’association entre le risque d’AOS et le changement dans la performance cognitive après trois ans dépend de l’âge et du sexe. Le risque élevé d’AOS est associé à un déclin de l’attention et de la vitesse de traitement de l’information, mais à un déclin de la mémoire épisodique uniquement chez les femmes âgées de 70 ans et plus. Cette thèse offre un éclairage nouveau quant aux facteurs pouvant moduler le lien observé entre l’AOS et la cognition dans les études épidémiologiques, ce qui pourra permettre de mieux dépister et prendre en charge les personnes apnéiques présentant un risque accru de déclin cognitif. / Thirty to 50% of the risk of developing dementia is attributable to modifiable factors such as physical inactivity, hypertension, and depression. In recent years, some authors have considered that sleep disorders should also be included. In particular, obstructive sleep apnea (OSA) is associated with a greater risk of cognitive decline and dementia according to epidemiological studies. However, other studies have not observed this link between OSA and cognitive decline. Our team thus hypothesized that certain factors modulate the association between OSA and cognitive decline, explaining part of the heterogeneity of the results seen in previous studies. This thesis aims to characterize the role of age, sex, and systemic inflammation in the association between OSA risk and cognitive performance in middle-aged and older adults. To achieve this, we used the score obtained from variants of the STOP questionnaire to establish the risk of presenting with OSA, a neuropsychological battery, and measurement of C-reactive protein (CRP) in the blood in a large Canadian cohort. This protocol has led to a narrative review and three research articles. The first article allowed to present an updated portrait of middle-aged and older adults at high- risk for OSA. Specifically, 17.5% of the cohort (21.9% in men and 13.1% in women) were identified as being at high-risk for OSA. In this study, risk factors for presenting with high-risk for OSA were age (≥ 55 years old), male sex, menopause, obesity, cardiovascular diseases, diabetes, cerebrovascular disease, anxio-depressive symptoms, and high levels of systemic inflammation. In the second article, we characterized the associations between OSA risk and cognitive performance according to age and sex. We showed that women at high-risk for OSA aged between 45 and 69 years have lower cognitive performance than those at low-risk for OSA, specifically in the areas of episodic memory and executive functions. We did not identify any association between OSA and cognitive performance in men. Additionally, we observed that systemic inflammation mediates some associations between OSA risk and executive functions in men and women younger than 70 years. In the third article, we observed that the association between OSA risk and change in cognitive performance after three years depends on age and sex. High-risk for OSA is associated with a decline in attention and information processing speed, but with a decline in episodic memory only in women aged 70 and older. This thesis sheds new light on the factors that can modulate the link observed between OSA and cognition in epidemiological studies, which may allow better screening and management of apneic individuals who present an increased risk of developing cognitive decline.

Background: Obesity has been associated with increased health care use, but it is unclear whether this is consistent across all measures of obesity. The objectives of this thesis were to compare obesity defined by four anthropometric measures, body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and percent body fat (%BF), and to estimate their associations with health care use among Canadian adults. Methods: A secondary data analysis was conducted from 30,097 individuals aged 45-85 years from the Canadian Longitudinal Study on Aging. Anthropometric measures were collected by trained research assistants and %BF, the reference standard, was measured using dual-energy x-ray absorptiometry. Obesity was defined as BMI≥30.0 kg/m2, WC≥88cm for females and ≥102cm for males, WHR≥0.85 for females and ≥0.90 for males, and %BF>35% for females and >25% for males. Approximately 18 months after baseline data collection, self-reported health care use in the past 12 months was collected, including any contact with a general practitioner, medical specialist, emergency department, and being a patient in a hospital overnight. Pearson correlation coefficients and sensitivity and specificity analyses were conducted to compare anthropometric measures to %BF. Relative risks and risk differences were calculated for measures of health care use, adjusted for sex, age, education, income, urban/rural, marital status, smoking status, and alcohol use. Secondary analyses were also stratified by sex and age. Results: The prevalence of obesity defined by BMI was 29%, by WC was 42%, by WHR was 62%, and by %BF was 73%. BMI and WC were highly correlated with %BF (r=0.75 and r=0.70, respectively) and WHR was weakly correlated with %BF (r=0.29). BMI and WC cut points demonstrated high specificity (>93%) and lower sensitivity (<58%) in predicting obesity defined by %BF. WHR cut points demonstrated high sensitivity (95%) and lower specificity (28%) in males, but lower sensitivity (44%) and high specificity (83%) in females in predicting %BF- defined obesity. There was an increased relative and absolute risk of health care use for all measures of obesity and all health care services. For example, WC-defined obesity was associated with increased relative risk (RR) of hospital overnight stay (RR: 1.40, 95% CI: 1.28- 1.54) and the risk difference (per 100) was 2.6 (95% CI:1.9-3.3). The risk of health care use was similar amongst females and males with obesity although relative risks and risk differences attenuated in the oldest adult group aged 75 and older compared to the youngest group aged 45- 54. Conclusion: The prevalence of obesity among Canadian adults varied substantially by anthropometric measure. BMI and WC have stronger correlations and concordance with %BF than does WHR, however all measures were positively associated with increased health care use. Further research should be conducted on obesity cut points to discern the best measure to predict health care use. / Thesis / Master of Public Health (MPH)