Shihoko Koyama

Dr. Shihoko Koyama

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Research Focus & Metrics

Academic Career Length

13Years (2014-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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18 March 2021 in BMJ Open
Verified
Journal Article
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TNTaiji Noguchi
Taiji Noguchi
MSMasashige Saito
Masashige Saito
JAJun Aida
Jun Aida
NNNoriko Cable, N
Noriko Cable, N
TTTaishi Tsuji
Taishi Tsuji
Katsunori KondoKatsunori Kondo
Katsunori Kondo
Objective Social isolation is a risk factor for depression in older age. However, little is known regarding whether its impact varies depending on country-specific cultural contexts regarding social relationships. The present study examined the association of social isolation with depression onset among older adults in England, which has taken advanced measures against social isolation, and Japan, a super-aged society with a rapidly increasing number of socially isolated people. Design Prospective longitudinal study. Setting We used data from two ongoing studies: the English Longitudinal Study of Ageing (ELSA) and the Japan Gerontological Evaluation Study (JAGES). Participants Older adults aged ≥65 years without depression at baseline were followed up regarding depression onset for 2 years (2010/2011–2012/2013) for the ELSA and 2.5 years (2010/2011–2013) for the JAGES. Primary outcome measure Depression was assessed with eight items from the Centre for Epidemiologic Studies Depression Scale for the ELSA and Geriatric Depression Scale for the JAGES. Multivariable logistic regression analysis was performed to evaluate social isolation using multiple parameters (marital status; interaction with children, relatives and friends; and social participation). Results The data of 3331 respondents from the ELSA and 33 127 from the JAGES were analysed. Multivariable logistic regression analysis demonstrated that social isolation was significantly associated with depression onset in both countries. In the ELSA, poor interaction with children was marginally associated with depression onset, while in the JAGES, poor interaction with children and no social participation significantly affected depression onset. Conclusions Despite variations in cultural background, social isolation was associated with depression onset in both England and Japan. Addressing social isolation to safeguard older adults’ mental health must be globally prioritised.

1 January 2014 in The Tohoku Journal of Experimental Medicine
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Journal Article
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SKShihoko Koyama
Shihoko Koyama
JAJun Aida
Jun Aida
IKIchiro Kawachi
Ichiro Kawachi
NKNaoki Kondo
Naoki Kondo
SSS V Subramanian
S V Subramanian
KOKen Osaka
Ken Osaka
The victims of the Great East Japan Earthquake and Tsunami have been forced to live in temporary housing, mainly by two different methods of resettlement: group allocation that preserved pre-existing local social ties and lottery allocation. We examined the effects of various factors, including the resettlement methods and social support, on mental health. From February to March 2012, we completed a cross-sectional survey of 281 refugees aged 40 years or older, who had lost their homes in the tsunami and were living in temporary housing in Iwanuma city. Psychological distress of the victims was assessed using the Kessler Psychological Distress Scale (K6) that consists of six self-reported items. Participants were also asked whether they had provided or received social support during this time. Participants were categorized as “providing social support” if they listened to someone else’s concerns and complaints, or “receiving social support” if they have someone who listened to their concerns and complaints. After adjusting for age and sex, multiple log-binomial regression analysis showed that participants without social support had a higher risk of psychological distress. Group allocation victims were more likely to receive social support than those who underwent lottery allocation. However, the resettlement approach did not significantly correlate with distress. Other factors associated with a higher risk of psychological distress were a younger age (55 or younger), living with either 3 people or 6 or more people, and having a lower income. The present results suggest that social support promotes the mental health of disaster victims.

5 June 2021 in Journal of Epidemiology
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Journal Article
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SKShihoko Koyama
Shihoko Koyama
Takahiro TabuchiTakahiro Tabuchi
Takahiro Tabuchi
SOSumiyo Okawa
Sumiyo Okawa
TKTakayoshi Kadobayashi
Takayoshi Kadobayashi
HSHisaya Shirai
Hisaya Shirai
IMIsao Miyashiro
Isao Miyashiro
OBJECTIVES: In April 2020, the Japanese government declared a state of emergency due to the COVID-19 pandemic and infection control measures, including requests to work from home and stay-at-home restrictions, were introduced. This study examined changes in smoking behavior during the COVID-19 state of emergency.METHODS: An online cross-sectional survey was conducted in Osaka, Japan. To assess differences in smoking behavior among 5,120 current smokers, before and after the declaration of a state of emergency, prevalence ratios (PRs) for two outcomes, increased smoking and quitting smoking, were calculated using multivariable Poisson regression, adjusting for potential covariates.RESULTS: We found 32.1% increased the number of cigarettes smoked and 11.9% quit smoking. After adjustment for all variables, we found risk factors for COVID-19 (men and older age group) had both significantly higher PR for quitting smoking (men; PR=1.38(1.17-1.62), 65 years old+; PR=2.45(1.92-3.12)) and significantly lower PR of increased smoking (men; PR=0.85(0.78-0.93), 65 years old+; PR=0.38(0.29-0.49)). Additionally, respondents working from home or living alone had significantly higher PR for increased smoking (working from home; PR=1.29(1.17-1.41), living alone; PR=1.23(1.10-1.38)) and respondents who changed from cigarettes to heated tobacco products (HTPs) had significantly lower PR for quitting smoking (PR=0.15(0.04-0.58)).CONCLUSIONS: We suggest people who have high-risk factors for COVID-19 might change their smoking behavior for the better, while people who work from home or live alone might change their smoking behavior for the worse, during the COVID-19 state of emergency. Additionally, changing from smoking cigarettes to using HTPs makes smokers less likely to quit.

1 May 2021 in Social Science & Medicine
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Journal Article
Open access
SKShihoko Koyama
Shihoko Koyama
MSMasashige Saito
Masashige Saito
NNNoriko Cable, N
Noriko Cable, N
TITakaaki Ikeda
Takaaki Ikeda
TTTaishi Tsuji
Taishi Tsuji
JAJun Aida
Jun Aida
In Western countries, the most important part of the face in communication is the mouth, whereas it is the eyes in Asian countries; thus oral health could be more important in social interactions in Western countries. Our aim was to examine differences in the association between oral health status and social isolation among older people by comparing Japan and England. We used cross-sectional information obtained from adults aged 65+ in two ongoing prospective cohort studies: The Japan Gerontological Evaluation Study (JAGES, N = 120,195) and the English Longitudinal Study of Ageing (ELSA, N = 3,958). The dependent variable, social isolation score (SIS) was calculated from five factors (marital status, social support from children, social support from family, social support from friends, and social participation). The independent variables were self-reported number of remaining teeth (0, 1-9, 10-19, ≥20) and denture use (≥20 teeth, 10-19 teeth with denture, 10-19 teeth without denture, 0-9 teeth with denture, 0-9 teeth without denture), while the covariates in the model were: sex, age, educational attainment, self-rated health, number of comorbidities, household annual equivalized income, mental health status, daily living activities, and smoking status. We examined associations between oral health status and SIS by applying an ordered logit model by country. Compared to England, more Japanese participants were socially isolated (1.4% vs. 5.8%), but fewer were edentulous (13.1% vs. 7.7%). In both countries, poorer oral health further increased the odds of being socially isolated. Pooled analysis of the ordered logit model with an interaction term showed that the association of number of remaining teeth with SIS was stronger in edentulous participants and in England (odds ratio = 1.50, 95% Confidence interval:1.26-1.80). In both countries, oral health was associated with social isolation; this association could be stronger in England than in Japan.

30 April 2016 in BMC Oral Health
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Journal Article
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SKShihoko Koyama
Shihoko Koyama
JAJun Aida
Jun Aida
KKKatsunori Kondo
Katsunori Kondo
TYTatsuo Yamamoto
Tatsuo Yamamoto
MSMasashige Saito
Masashige Saito
KOKen Osaka
Ken Osaka
Being homebound is an important risk factor of functional disability in older people. There is a possibility of bidirectional relationship between homeboundness and dental health. This prospective cohort study examined the association of dental health, which includes social function, on homeboundness in the future. The participants were ≥ 65 years, responded to two postal surveys conducted in 2006 and 2010, and were not homebound at baseline. Logistic regression analysis was used to estimate the odds ratios for homeboundness, defined as going out of one’s home less than once weekly. Self-reported baseline dental status was used as the main predictor. Age, sex, marital status, educational attainment, income, comorbidity, depression, walking time, living alone, and area of residence were used as covariates. Among 4390 non-homebound respondents, 7.4 % were homebound four years later. The proportions of homebound respondents with < 20 teeth without dentures, < 20 teeth with dentures, and ≥ 20 teeth were 9.7, 8.8, and 4.4 %, respectively. The odds for being homebound in the 65–74-year age group, adjusted for covariates, was 1.78 (95 % CI: 1.01–3.13; p < 0.05) times higher for respondents with < 20 teeth and no dentures than that for respondents with ≥ 20 teeth. Among the participants in the ≥ 75-year age group, a significant association of homeboundness and dental health was not observed. Among the young-old population, poor dental health predicted future onset of homeboundness, while depressive symptoms did not show any significant association.

21 December 2020 in Geriatrics & Gerontology International
Verified
Journal Article
Open access
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MSMasashige Saito
Masashige Saito
JAJun Aida
Jun Aida
NNNoriko Cable, N
Noriko Cable, N
PZPaola Zaninotto
Paola Zaninotto
TITakaaki Ikeda
Takaaki Ikeda
KKKatsunori Kondo
Katsunori Kondo
Aim: Existing evidence links social isolation with poor health. To examine differences in the mortality risk by social isolation, and in socio‐economic correlates of social isolation, we analyzed large‐scale cohort studies in Japan and England.Methods: Participants were drawn from the Japan Gerontological Evaluation Study (JAGES) and the English Longitudinal Study of Ageing (ELSA). We analyzed the 10‐year mortality among 15 313 JAGES participants and 5124 ELSA respondents. Social isolation was measured by two scales, i.e., scoring the frequency of contact with close ties, and a composite measurement of social isolation risk. We calculated the population attributable fraction, and Cox regression models with multiple imputations were used to estimate hazard ratios (HRs) for mortality due to social isolation.Results: The proportion of those with contact frequency of less than once a month was 8.5% in JAGES and 1.3% in ELSA. Males, older people, those with poor self‐rated health, and unmarried people were significantly associated with social isolation in both countries. Both scales showed that social isolation among older adults had a remarkably higher risk for premature death (less frequent contact with others in JAGES: hazard ratio [HR] = 1.18, 95% confidence interval [CI]: 1.05–1.33, in ELSA: HR = 1.27, 95% CI: 0.85–1.89; and high isolation risk score in JAGES: HR = 1.30, 95% CI: 1.12–1.50, in ELSA: HR = 2.05, 95% CI: 1.52–2.73). The population attributable fraction showed less frequent contact with close ties was attributed to about 18 000 premature deaths annually in Japan, in contrast with about 1800 in England.Conclusions: Negative health impacts of social isolation were higher among older Japanese compared with those in England. Geriatr Gerontol Int 2021; 21: 209–214.