Open access

Original research

Taiji Noguchi ‍ ‍,1,2 Masashige Saito ‍ ‍,3 Jun Aida ‍ ‍,4,5 Noriko Cable ‍ ‍,6
Taishi Tsuji ‍ ‍,7,8 Shihoko Koyama ‍ ‍,9 Takaaki Ikeda ‍ ‍,10,11 Ken Osaka ‍ ‍,11
Katsunori Kondo ‍ ‍8,12

To cite: Noguchi T, Saito M,
Aida J, et al. Association
between social isolation anddepression onset amongolder adults: a cross-­national
longitudinal study in Englandand Japan. BMJ Open
2021;11:e045834. doi:10.1136/
bmjopen-2020-045834►► Prepublication history andadditional material for this paper
is available online. To view thesefiles, please visit the journal
online (http://​dx.d​ oi.​org/​10.​1136/b​ mjopen-​2020-0​ 45834).

Received 13 October 2020
Revised 19 February 2021
Accepted 22 February 2021

© Author(s) (or theiremployer(s)) 2021. Re-­use
permitted under CC BY.
Published by BMJ.
For numbered affiliations see
end of article.
Correspondence to
Mr Taiji Noguchi;​noguchi.​taiji0415@g​ mail.​com

ABSTRACT
Objective Social isolation is a risk factor for depressionin older age. However, little is known regarding whether
its impact varies depending on country-­specific culturalcontexts regarding social relationships. The present
study examined the association of social isolation withdepression 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: theEnglish 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 assessedwith 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 withchildren, relatives and friends; and social participation).
Results The data of 3331 respondents from the ELSA
and 33 127 from the JAGES were analysed. Multivariablelogistic regression analysis demonstrated that social
isolation was significantly associated with depression
onset in both countries. In the ELSA, poor interaction withchildren was marginally associated with depression onset,
while in the JAGES, poor interaction with children and nosocial participation significantly affected depression onset.
Conclusions Despite variations in cultural background,social isolation was associated with depression onset inboth England and Japan. Addressing social isolation tosafeguard older adults’ mental health must be globallyprioritised.

INTRODUCTION
With population ageing, there is growing
worldwide interest in social issues concerning
older adults, including social isolation andthe deterioration of physical and mental

Strengths and limitations of this study►► This is the first cross-­national longitudinal study to

examine the association between social isolationand depression onset in England, which has taken
advanced measures against social isolation, andJapan, a super-­aged society with a rapidly increasing number of socially isolated people.
►► This study included a large sample of over 3300 individuals from England and 33 000 individuals fromJapan aged 65 years and older.
►► A limitation of this study is that we cannot makedirect comparisons because of variations in cohort
follow-­up periods and depression measurement.
►► Another limitation is the use of social support for
the evaluation of social contact so as to permit theuse of the same social isolation assessment scale inboth countries.

health. Defined as an objective state in where
an individual has few close relationships orlimited contact within a community,1 social
isolation is recognised as a social determinantof health with relevance to mortality,2 cardiovascular diseases,3 dementia4 and mental
health.5 6 Social isolation is a major risk
factor for mental health problems in older
age. Several systematic reviews have demonstrated that social isolation is associatedwith depressive symptoms,5 6 which, in turn,are correlated with unhealthy behaviours
and reduced access to material resources.7
Depression, common in later life, is related
to adverse health outcomes such as poor
quality of life8 and functional disability.9 With
the high current global burden of depression expected to increase further by 2030,10
addressing social isolation is an important
gerontological issue for protecting mental
health among older adults.

Noguchi T, et al. BMJ Open 2021;11:e045834. doi:10.1136/bmjopen-2020-045834

1

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Association between social isolation anddepression onset among older adults: across-­national longitudinal study inEngland and Japan

Open access

2studies are needed to address temporality. However,previous cross-­national comparative studies have
employed only cross-­
sectional designs.22 23 Therefore,
using longitudinal data from both countries, the present
study aims to investigate the association of social isolation with depression onset in England, which has taken
advanced measures against social isolation, and Japan, asuper-­aged society with a rapidly increasing number ofsocially isolated people.

METHODS
SampleThis longitudinal study was conducted using data fromtwo ongoing prospective cohort studies: the English
Longitudinal Study of Ageing (ELSA) and the Japan
Gerontological Evaluation Study (JAGES). The ELSA
targets independent-­living older adults aged ≥50, while
JAGES participants are community-­dwelling individuals
term healthcare
aged ≥65 who are ineligible for long-­
insurance benefits.25 Details of the ELSA and JAGES canbe found elsewhere.26 27 For the present analysis, we used
the two waves of data that most closely corresponded withthe timing of our study: wave 5 (2010/2011) to wave 6(2012/2013) for the ELSA, and wave 1 (2010/2011) towave 2 (2013) for the JAGES. We harmonised the data by
including older adults aged ≥65, independent in activities
of daily living, and without self-­reported dementia. For
analysis, respondents who scored above the cut-­off point
for depression on each measure in the respective cohort
at baseline were excluded and we followed up the onset
of depression for 2 years for the ELSA and 2.5 years for
the JAGES.
Depression
Based on a previous cross-­national study,28 depressive
symptoms were measured both at baseline and follow-­up
using eight items from the Centre for Epidemiologic
Studies Depression Scale (CES-­D 8) in the ELSA29 and
the Geriatric Depression Scale (GDS-15) in the JAGES.30
To identify possible depressive cases, the CES-­D 8 cut-­offwas ≥4 while that for the GDS-15 was ≥5.31 32 As previously
mentioned, respondents with depression at baseline were
excluded and we observed the onset of depression during
the follow-­up.
Social isolation
Social isolation levels were assessed using a modified
version of the Social Isolation Index (SII).33–35 The index
was computed with respondents given a point if they:(1) were unmarried or living alone, (2) had poor interaction with children (did not live with their children or
had no one to provide emotional or instrumental social
support), (3) had poor interaction with relatives (did nothave immediate family members providing emotional or
instrumental social support), (4) had poor interaction
with friends (less than monthly contact or no friends who
could provide emotional or instrumental social support)
Noguchi T, et al. BMJ Open 2021;11:e045834. doi:10.1136/bmjopen-2020-045834

BMJ Open: first published as 10.1136/bmjopen-2020-045834 on 18 March 2021. Downloaded from http://bmjopen.bmj.com/ on April 29, 2021 by guest. Protected by copyright.

The impacts of social isolation on health may vary bycountry; this could be the result of differences in thesocial environments related to social networks within
and outside the family. A recent study of older adults
in England and Japan showed that social isolation is acommon risk factor for mortality in both countries, witha greater impact observed in England; the results are
discussed in terms of possible differences between societies that are highly connected and those that are not.11
In the UK, in recognition of the impact of social isolation
on health and economic loss, the position of ‘Minister ofLoneliness’ was established in 2018, and the country istaking a progressive approach to the elimination of social
isolation.12 In contrast, Japan, now a super-­aged society(more than 21% of the population aged 65 or above),13
is experiencing a rapidly increasing trend in the numberof never-­married persons and weakening communityand neighbourhood relations,14 leading to a rise in thenumber of socially isolated individuals.15 In Japan, theproportion of people who rarely or never spend timewith those close to them has been reported to be thehighest among Organisation for Economic Co-­operation
and Development countries. In particular, this figure ismuch higher than in the UK, which has made advances
in tackling social isolation (Japan=15.3%, UK=5.0%).16
Owing to differences in social structures and the contexts
surrounding social isolation, the impact of social isolation
on depression is expected to vary across countries.
Furthermore, the health effects of social isolation may
differ depending on the cultural context of social relationships. In East Asian countries, including Japan, there
is a familial norm based on the traditional culture offilial piety,17 which is often contrasted with individualismin Western countries.18 19 Based on this cultural background, Japanese social support networks may be kinshipcentred, which may be narrower than the types of social
networks prevalent in other countries.20 However, there
is a lack of consensus on the health effects of social relationships based on these cultural differences. A previous
cross-­
national study showed that among English men,friendship-­based social relationships had a significant
impact on longevity, whereas among Japanese men, this
impact was associated with family-­based social relationships.21 In contrast, a study of older adults in the USA andJapan demonstrated that while relationships with children were associated with a low level of depression onlyin Japan, the presence of spouses was important in bothcountries, but more so in the USA.22 Another comparative study among adults suggested that social contact withfriends benefited women’s mental health in the UK but
not in Japan.23 Thus, the family-­oriented nature of East
Asian societies does not automatically imply the healthimportance of family-­based relationships, and the roles ofindividual components of social isolation (family, friends
and others) in the mental health of older adults in eachcountry remain controversial.
As the association between social isolation and depression is often described as bidirectional,24 longitudinal

Open accessCovariates
The covariates included age, gender, educational attainment, household equivalised income, present illness, self-­
rated health, smoking and drinking. Age was categorised
as 65–69, 70–74, 75–79, 80–84 and ≥85. Based on the agesof respondents who had completed formal education,
the age of final educational attainment was categorisedas ≤15 years, 16–18 years and ≥19 years. Household equivalised income was classified into quintiles. Present illness
was classified as ‘yes’ or ‘no’ for cancer, heart disease
and stroke. Self-­rated health was dichotomised as ‘poor’and ‘good’. Smoking and drinking were dichotomised as‘never/past’ and ‘current’.
Statistical analysis
We analysed the ELSA and JAGES data separately becauseof differences in research design, especially sampling
approaches. A longitudinal weight was applied to accountfor survey non-­response for the ELSA but not the JAGES as
its design does not allow it. First, we calculated descriptive
statistics. Second, we conducted a multivariable logistic
regression analysis to examine the association between
SII score and depression onset and obtained ORs and
95% CIs for depression onset. Model 1 was not adjusted
for covariates while Model 2 was adjusted for all covariates. Additionally, we analysed the association between
SII subcomponents and depression onset, adjusted for all
covariates.
To mitigate potential biases resulting from missing
information, we used the multiple imputation approach
under the missing at random assumption. We generated
20 imputed datasets for the final analysis, which excluded
those who met the exclusion criteria and did not respondto the follow-­up surveys, using the multiple imputationby chained equations procedure and pooled the results
using Rubin’s rule.36
The significance level was set at P<0.05. We used R(V.3.5.2 for Windows) for all statistical analyses.
Patient and public involvement
No patients were involved in the development of theresearch question, study design or data interpretation.

RESULTSA total of 3331 ELSA respondents and 33 127 JAGES
respondents were included in the final analysis. Theirbaseline characteristics are presented in table 1. The meanage (SD) was 73.6 (6.9) years for the ELSA and 72.4 (5.4)
years for the JAGES. Regarding SII scores, the ELSA had
Noguchi T, et al. BMJ Open 2021;11:e045834. doi:10.1136/bmjopen-2020-045834

the largest number of respondents with 0 and 1 points,
while the JAGES had the largest number with 2 and 3
points. In the ELSA, respondents who were older, male,less educated, had a lower income, had heart disease, hadpoor self-­rated health, smoked, consumed little alcoholand had higher baseline depressive symptom scores andhigher SII scores. A similar trend was observed in the
JAGES, but here, those who consumed more alcohol had
higher SII scores.
Table 2 presents the description of social isolation anddepression onset. At follow-­up, 201 (6.0%) ELSA respondents and 4456 (13.5%) JAGES respondents exhibited
depression onset. In both studies, higher SII scores wereassociated with an increased risk of depression onset.
Regarding SII subcomponents, ELSA respondents who
were unmarried or living alone were more likely to havedepression, while this was the case with JAGES respondents with no social participation.
Table 3 depicts the association between SII scores anddepression onset. Multivariable analysis showed that higher
SII scores were associated with a higher risk of depression
onset in both studies after adjusting for all covariates. In the
ELSA, the OR of depression onset was significantly higher
from a score ≥1 point (OR [95% CI] compared with zero
points, one: 1.68 [1.02 to 2.75], two: 1.77 [1.03 to 3.05],
three: 2.64 [1.37 to 5.12], ≥four: 4.01 [1.43 to 11.22], P for
trend=0.015). In the JAGES, as SII scores increased, the OR of
depression onset gradually increased, reaching significanceat ≥three points (OR [95% CI] compared with zero points,
one: 1.10 [0.89 to 1.35], two: 1.15 [0.94 to 1.40], three: 1.28
[1.04 to 1.56], ≥four: 1.48 [1.18 to 1.85], P for trend <0.001).
These results showed almost the same tendency as thecomplete case analysis without multiple imputation (online
supplemental table 1).
Table 4 presents the associations of SII subcomponents
with depression onset. In the ELSA, subcomponents were
not significant, although poor interaction with children was
marginally significant (OR [95% CI]) with ‘none’ as thereference; unmarried or living alone: 1.13 [0.80 to 1.60],
poor interaction with children: 1.55 [1.00 to 2.41], poorinteraction with relatives: 1.24 [0.79 to 1.94], poor interaction
with friends: 1.15 [0.77 to 1.71], no social participation: 1.22
[0.80 to 1.87]). In the JAGES, poor interaction with children
and no social participation were significantly associated withdepression onset after adjusting for all covariates (OR [95%CI], with ‘none’ as the reference; unmarried or living alone:
1.11 [1.00 to 1.24], poor interaction with children: 1.09 [1.01
to 1.19], poor interaction with relatives: 1.04 [0.96 to 1.12],
poor interaction with friends: 1.03 [0.95 to 1.11], no social
participation: 1.28 [1.17 to 1.40]). These results were similar
to those obtained from the complete case analysis (online
supplemental table 2).
DISCUSSION
To the best of our knowledge, this is the first cross-­national
longitudinal study of the association of social isolation withdepression among older English and Japanese adults. Social
3

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and (5) had no social participation (no participation inany social or religious groups). The total possible score
ranged from 0 to 5, with higher scores indicating greatersocial isolation. The participants were categorised into
the following five groups based on their scores: 0, 1, 2, 3
and 4–5 points. We used the total score and the scores ofthe five subcomponents as predictive variables.

Open access

ELSA*

JAGES

Social Isolation Index score†Social Isolation Index score†

0

1

2

3

≥4

0

1

2

3

≥4

n=905
(27.2%)

n=1049(31.5%)

n=596(17.9%)

n=216(6.5%)

n=49(1.5%)

n=1402(4.2%)

n=5981(18.0%)

n=9723(29.4%)

n=8735(26.4%)

n=2176(6.6%)

Age (years), (%) 65–69

41.0

36.4

29.9

27.6

28.3

38.6

40.5

38.0

37.0

35.8

 70–74

26.1

28.3

28.8

29.3

23.6

32.1

32.5

31.6

31.0

30.4

 75–79

20.9

17.5

19.3

15.8

20.4

19.2

18.3

19.5

20.3

21.9

 80–84

9.1

12.2

12.5

14.5

15.5

8.3

6.7

8.3

9.0

8.8

 ≥85

2.8

5.7

9.5

12.8

12.2

1.9

2.0

2.6

2.7

3.1

 Men

50.0

46.1

45.3

51.9

65.8

27.2

35.1

47.0

64.4

66.1

 Women

50.0

53.9

54.7

48.1

34.2

72.8

64.9

53.0

35.6

33.9

Gender, (%)

Educational attainment (years), (%)
 ≤15

44.1

51.3

52.3

60.9

69.6

42.9

38.1

37.9

38.7

48.6

 16–18

35.0

33.8

34.6

27.5

14.1

40.9

40.8

39.3

36.8

31.1

 ≥19

17.8

12.5

11.0

10.3

14.0

15.7

20.4

21.8

23.3

18.5

 Missing

3.2

2.4

2.1

1.3

2.3

0.5

0.7

0.9

1.2

1.8

Household equivalised income, (%) First quintile(lowest)

11.4

18.3

23.2

31.2

14.4

7.4

10.9

13.9

15.6

21.3

 Second quintile

21.5

23.7

26.1

24.1

29.6

13.2

13.5

15.0

15.5

16.4

 Third quintile

20.9

21.8

18.9

19.5

27.1

22.5

30.6

30.3

30.6

28.0

 Fourth quintile

21.9

19.9

18.1

16.5

16.6

14.3

13.6

12.7

11.3

9.5

 Fifth quintile(highest)

22.7

15.0

12.7

8.3

12.4

31.5

22.5

19.2

16.8

12.9

 Missing

1.5

1.3

0.9

0.4

0.0

11.1

8.9

8.9

10.2

11.9

 No

96.5

95.8

97.1

97.5

96.5

91.0

91.2

90.8

90.1

89.7

 Yes

3.4

4.2

2.9

2.5

3.5

3.2

3.1

3.1

3.4

3.7

 Missing

0.1

0.0

0.0

0.0

0.0

5.8

5.7

6.1

6.5

6.6

 No

90.7

86.9

88.4

88.3

77.3

91.0

91.2

90.8

90.1

89.7

 Yes

9.3

13.0

11.6

11.7

22.7

3.2

3.1

3.1

3.4

3.7

 Missing

0.0

0.1

0.0

0.0

0.0

5.8

5.7

6.1

6.5

6.6

 No

96.3

96.1

97

94.4

96.6

93.3

93.6

93.1

92.5

92.2

 Yes

3.7

3.8

3.0

5.6

3.4

0.9

0.8

0.8

1.0

1.2

 Missing

0

0.1

0.0

0.0

0.0

5.8

5.7

6.1

6.5

6.6

Cancer, (%)

Heart disease, (%)

Stroke, (%)

Self-­rated health, (%) Good

86.4

79.9

78.8

75.4

71.3

92.0

91.7

90.6

90.2

87.2

 Poor

13.6

20.1

21.2

24.6

28.7

7.2

7.7

8.6

9.0

12.2

 Missing

0.0

0.0

0.0

0.0

0.0

0.8

0.5

0.8

0.8

0.6

95.5
4.5

93.1
6.9

89.8
10.2

82.9
17.1

89.4
10.6

86.4
6.4

86.1
7.4

82.9
9.5

81.5
11.3

78.4
14.2

Smoking, (%) Never/past Current

Continued

4

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Table 1 Respondents’ baseline characteristics

Open access

ELSA*

JAGES

Social Isolation Index score†Social Isolation Index score†

0

1

2

3

≥4

0

1

2

3

≥4

n=905
(27.2%)

n=1049(31.5%)

n=596(17.9%)

n=216(6.5%)

n=49(1.5%)

n=1402(4.2%)

n=5981(18.0%)

n=9723(29.4%)

n=8735(26.4%)

n=2176(6.6%)

0.0

0.0

0.0

0.0

0.0

7.1

6.5

7.5

7.2

7.3

 Never/past

7.5

11.8

14.9

25.8

17.3

65.0

60.0

56.5

50.4

55.0

 Current

91.3

87.0

82.9

72.6

73.6

30.2

35.7

38.6

44.7

40.4

 Missing

1.3

1.2

2.2

1.6

9.2

4.8

4.3

4.9

4.9

4.6

 0

20.5

30.4

29.0

26.4

24.3

 1

25.5

28.4

28.6

26.9

27.0

 2

22.5

20.0

19.8

21.5

21.1

 3
 4

17.5
14.1

13.1
8.1

13.5
9.1

14.7
10.5

15.9
11.7

 Missing
Drinking, (%)

CES-­D 8 score at baseline,
(%)
 0

57.2

52.0

45.5

42.2

54.0

 1

27.3

26.2

28.6

31.8

25.5

 2

9.8

13.8

17.1

11.9

15.1

 3

5.7

8.0

8.8

14.2

5.4

GDS score at baseline, (%)*ELSA data after sampling weight.
†Missing data: ELSA, n=516; JAGES, n=5110.
CES-­D 8, eight items from the Centre for Epidemiologic Studies Depression Scale; ELSA, English Longitudinal Study of Ageing; GDS,
Geriatric Depression Scale; JAGES, Japan Gerontological Evaluation Study.

isolation was significantly associated with depression onset
in both countries. Our results support previous longitudinalfindings on social relationships and mental health amongolder adults in England37 and Japan.38 Using data framesthat were similar with regard to assessment and covariates, wedemonstrated that social isolation is a common risk factor for
depression in England and Japan, despite country-­specificcultural differences regarding social relationships. Thus, ourresults suggest that to safeguard the mental health of older
adults, addressing social isolation is a global need.
The association between social isolation and depression
was somewhat stronger in England than in Japan. These
results are similar to a previous report concerning mortality
among older adults in England and Japan.11 Although wecannot make direct comparisons due to variations in cohort
follow-­up periods and depression measurement, there areseveral possible reasons for this pattern of findings. The
impact of social factors could differ depending on the groupand society to which one belongs. This is best understood in
the context of the concept of relative deprivation.39 In otherwords, higher levels of relative social isolation may induce
greater psychological stress. A previous study showed thatrich community ties and cohesion were protective factors forhealth but could have a negative effect on those who were
not socially involved.40 Being isolated in a connected society

such as the UK may represent a more severe condition, witha stronger negative impact on mental health.
Our results revealed that poor interaction with children
was significant with regard to depression onset in Japan. In
England, while the association was marginal, of the components of social isolation, poor interaction with children had
the greatest effect. The lack of interaction with children
could have an adverse effect on the mental health of older
adults in both countries. Previous studies in England41 andJapan22 have reported that social support from children cancontribute to alleviating depression, and our results pointin the same direction. Older adults without children can beconsidered a vulnerable group, because adult children, inparticular, are often the main source of positive social support
for older parents.42 Older parents have certain expectations
with regard to receiving support from their children, andsituations wherein these expectations are not met may leadto depressive mood.43 However, a previous study reported noassociation between the presence of children and depression
among older adults in the USA.22 Owing to strong spousal
relationships in the USA, the effect of the presence of children might be relatively small. Thus, our study confirmed theadverse effects of poor interaction with children common
to England and Japan, but international generalisability can
only be established based on further research considering

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Table 1 Continued

Open access

ELSA*

Social Isolation Index score, (%)
 0

JAGES

CES-­D 8 score at follow-­up

GDS score at follow-­up

<4

≥4

<5

≥5

n=3130(94.0%)

n=201(6.0%)

n=28 671(86.5%)

n=4456(13.5%)

27.5

13.5

4.4

3.0

 1

31.2

29.3

18.6

14.3

 2

17.9

18.9

29.8

26.3

 3

6.5

10.1

26.2

27.5

 ≥4

1.5

2.9

6.1

9.3

 Missing

15.4

25.3

14.8

19.7

71.9

58.5

88.3

85.2

Social Isolation Index sub-­components, (%) Unmarried or living alone
  
No
  
Yes

28.1

41.5

10.2

12.7

  
Missing

0.0

0.0

1.4

2.1

 Poor interaction with children

81.8

73.4

26.6

25.0

12.5

14.7

71.7

72.9

  
No
  
Yes
  
Missing

5.7

11.8

1.7

2.1

 Poor interaction with relatives

76.3

68.1

41.1

38.7

  
No
  
Yes

17.3

18.6

54.4

56.0

  
Missing

6.4

13.4

4.5

5.4

 Poor interaction with friends

72.2

66.0

37.1

31.2

18.4

21.6

58.2

63.8

  
No
  
Yes
  
Missing

9.4

12.4

4.6

5.0

 No social participation

61.7

46.3

75.0

63.9

28.4
10.0

32.5
21.2

13.0
11.7

20.0
16.1

  
No
  
Yes
  
Missing*ELSA data after sampling weight.
CES-­D 8, eight items from the Centre for Epidemiologic Studies Depression Scale; ELSA, English Longitudinal Study of Ageing; GDS,
Geriatric Depression Scale; JAGES, Japan Gerontological Evaluation Study.

the cultural background of family relationships in individual
countries.
Although traditionally Japan is a country in which adultchildren are expected to demonstrate reciprocity with theirparents based on the strong family and kinship-­based cultural
background,44 in this study, the effect of interaction with children on depression was relatively modest. In recent years,
with trends such as adult children commonly living apartfrom their parents after marriage45 and the development ofpublic long-­term care services for the ageing population,46
Japan’s family system has become less traditional. Therefore, interaction with children may not be as essential tothe health of older adults as before. However, despite thesecultural transitions, we believe that interaction with children
has some value with regard to preventing depression in old
age in Japan.
Social participation was a strong protective factor for
depression onset in Japan, whereas there was no association
in England, although the OR was somewhat greater. Several
previous studies have reported that social participation helps
prevent depression onset.37 47–49 Our results pertaining toJapan support these reports. However, the protective effects
of social participation on mental health vary depending on
the type of organisation with which an individual is involved,48

6

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Table 2 Description of social isolation status and depression onset

Open access

ELSA

JAGES

Crude OR (95% CI)

Adjusted OR (95% CI)

Crude OR (95% CI)

Adjusted OR (95% CI) 01.00 (reference)

1.00 (reference)

1.00 (reference)

1.00 (reference) 1

1.92** (1.19 to 3.10)

1.68* (1.02 to 2.75)

1.14 (0.94 to 1.39)

1.10 (0.89 to 1.35) 2

2.15** (1.28 to 3.62)

1.77* (1.03 to 3.05)

1.32** (1.09 to 1.60)

1.15 (0.94 to 1.40) 3

3.19*** (1.73 to 5.90)

2.64** (1.37 to 5.12)

1.57*** (1.30 to 1.90)

1.28* (1.04 to 1.56) ≥4

3.85** (1.46 to 10.18)

4.01** (1.43 to 11.22)

2.26*** (1.83 to 2.79)

1.48*** (1.18 to 1.85)

P for trend <0.001

P for trend=0.015

P for trend <0.001

P for trend <0.001

Social Isolation Index score

Adjusted for age, gender, educational attainment, household equivalised income, present illness (cancer, heart disease, and stroke), self-­rated health,smoking, drinking, and depression score at baseline (eight items from the Centre for Epidemiologic Studies Depression Scale for the ELSA and
Geriatric Depression Scale for the JAGES).
*P<0.05; **P<0.01; ***P<0.001.
ELSA, English Longitudinal Study of Ageing; JAGES, Japan Gerontological Evaluation Study.

the individual’s attitude towards participation,48 and theduration37 and frequency49 of participation. Regarding thepresent study, in the English context, the role of social participation in depression prevention might have been unidentifiable due to differences in the effects of these participation
contexts. We took into account only social participation,
without delving into specific types. Thus, the context of effective social participation, such as type, duration, and role in
the organisation in both countries, requires further investigation. Despite these challenges, our findings suggest thatin Japan, social isolation prevention measures based on the
promotion of social participation could be beneficial for safeguarding the mental health of older adults.
This study has several strengths. First, it is the first cross-­national population-­level investigation of the association ofsocial isolation with depression onset using a unified data
frame. Second, by using two longitudinal datasets, we wereable to examine the prospective association between social
isolation and depression. Third, the use of large-­scale data
allowed us to detect the effects of relatively rare situations ofsevere social isolation.

However, certain limitations cannot be ignored. First, themeasurement of depression in the two cohorts was not thesame. Therefore, we could not directly compare depression
onset in the two countries. However, these measurements
were also used in a previous cross-­national comparison study
in England and Japan,28 and we were able to examine theassociation between social isolation and depression onset inboth countries using the same data frame. Second, we usedsocial support for the assessment of social contact for someitems in order to be able to use the same SII. Therefore,
cultural differences in expectations regarding the receipt
of social support in both countries might have caused information biases. For instance, expectations regarding social
support from relatives could originally have been higher inJapan,44 leading to overestimation of social isolation levels.
Third, regarding the items of the SII, the questions and their
response options in the ELSA and JAGES were not exactly
the same, nor were they strictly authorised through procedures such as reverse translation and confirming reliability
and validity. However, we believe it is certainly meaningful toevaluate social isolation using the same framework. Finally,

Table 4 Association between subcomponents of social isolation and depression onset: multivariable logistic regression
analysis
ELSA

JAGES

Adjusted OR (95% CI)

Adjusted OR (95% CI)

Social Isolation Index subcomponents (reference: none) Unmarried or living alone

1.13 (0.80 to 1.60)

1.11† (1.00 to 1.24) Poor interaction with children

1.55† (1.00 to 2.41)

1.09* (1.01 to 1.19) Poor interaction with relatives

1.24 (0.79 to 1.94)

1.04 (0.96 to 1.12) Poor interaction with friends

1.15 (0.77 to 1.71)

1.03 (0.95 to 1.11) No social participation

1.22 (0.80 to 1.87)

1.28*** (1.17 to 1.40)

Adjusted for age, gender, educational attainment, equivalent income, present illness (cancer, heart disease and stroke), self-­rated health,smoking, drinking and depression score at baseline (eight items from the Centre for Epidemiologic Studies Depression Scale for the
ELSA and Geriatric Depression Scale for the JAGES).
*P<0.05; ***P<0.001;†P<0.1.
ELSA, English Longitudinal Study of Ageing; JAGES, Japan Gerontological Evaluation Study.

Noguchi T, et al. BMJ Open 2021;11:e045834. doi:10.1136/bmjopen-2020-045834

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Table 3 Association between social isolation and depression onset: multivariable logistic regression analysis

Open access

CONCLUSION
We examined the association between social isolation anddepression onset among older adults in England and Japan,
who experience different cultural contexts regarding social
relationships, and found a significant association in bothcountries; we also observed that in England, poor interaction
with children was marginally associated, and in Japan, poorinteraction and lack of social participation were significantly
associated with depression. Tackling social isolation must be
prioritised to safeguard the mental health of older adults
worldwide. Particularly in Japan, the promotion of interaction with children and social participation could be key
factors in addressing social isolation.
Author affiliations
1
Department of Social Science, Center for Gerontology and Social Science, National
Center for Geriatrics and Gerontology, Obu, Japan2
Department of Public Health, Nagoya City University Graduate School of Medical
Sciences and Medical School, Nagoya, Japan
3
Faculty of Social Welfare, Nihon Fukushi University, Chita-­gun, Japan
4
Department of Oral Health Promotion, Tokyo Medical and Dental University
Graduate School of Medical and Dental Sciences, Bunkyo-­ku, Japan
5
Division for Regional Community Development, Liaison Center for Innovative
Dentistry, Tohoku University, Sendai, Japan
6
Department of Epidemiology and Public Health, University College London, London,
UK
7
Faculty of Health and Sport Sciences, University of Tsukuba, Tokyo, Japan
8
Department of Social Preventive Medical Sciences, Center for Preventive Medical
Sciences, Chiba University, Chiba, Japan
9
Cancer Control Center, Osaka International Cancer Institute, Osaka, Japan10
Department of Health Policy Science, Yamagata University Faculty of Medicine
Graduate School of Medical Science, Yamagata, Japan
11
Department of International and Community Oral Health, Tohoku University
Graduate School of Dentistry School of Dentistry, Sendai, Japan
12
Department of Gerontological Evaluation, Center for Gerontology and Social
Science, National Center for Geriatrics and Gerontology, Obu, Japan
Twitter Noriko Cable @nkcable
Acknowledgements We wish to express our deepest gratitude to the membersin the Japan Gerontological Evaluation Study. We would also like to thank everyone
who participated in the surveys.
Contributors All authors contributed to the conception and design of this study.
Data collection was primarily conducted by MS, JA, NC, KO and KK. Analyses were
performed by TN, MS, JA, TT, SK and TI. TN prepared the initial manuscript and MS,
JA, NC, TT, SK, TI, KO, and KK significantly contributed to revising it. All authors readand approved the final manuscript.

Research. The funding is currently provided by the National Institute of Aging(R01AG017644) and a consortium of UK government departments coordinated by
the National Institute for Health Research. The Japan Gerontological Evaluation
Study is supported by the Ministry of Education, Culture, Sports, Science andTechnology-­Japan-­Supported Program for the Strategic Research Foundation
at Private Universities (2009-2013), Japan Society for the Promotion of Science
KAKENHI Grant Numbers (JP18390200, JP22330172, JP22390400, JP23243070,
JP23590786, JP23790710, JP24390469, JP24530698, JP24683018, JP25253052,
JP25870573, JP25870881, JP26285138, JP26882010, JP15H01972), Health
Labour Sciences Research Grants (H22-­Choju-­Shitei-008, H24-­Junkanki -Ippan007, H24-­Chikyukibo-­Ippan-009, H24-­Choju-­Wakate-009, H25-­Kenki-­Wakate-015,
H25-­Choju-­Ippan-003, H26-­Irryo-­Shitei-003 [Fukkou], H26-­Choju-­Ippan-006,
H27-­Ninchisyou-­Ippan-001, H28-­chojuIppan-002, H28-­Ninchisho-­Ippan-002,
H30-­Kenki-­Ippan-006, H30-­Junkankitou-­Ippan-004), Japan Agency for Medical
Research and Development (JP17dk0110017, JP18dk0110027, JP18ls0110002,
JP18le0110009, JP19dk0110034), Research Funding for Longevity Sciencesfrom the National Center for Geriatrics and Gerontology (24-17, 24-23, 29-42,
30-22, 20-40), Open Innovation Platform with Enterprises, Research Institute andAcademia (OPERA, JPMJOP1831) from the Japan Science and Technology Agency,
and a Research Grant from the Health Science Center Foundation (2019-2020).
The funding sources had no role in the study design, data collection and analysis,
decision to publish or preparation of the manuscript.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The ELSA investigators received ethical approval for all waves ofthe study from the National Health Service Research Ethics Committees under the
National Research and Ethics Services (MREC/01/2/91). The JAGES protocols wereapproved by the Ethics Committee on the Research of Human Subjects at Nihon
Fukushi University (10-05).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data may be obtained from a third party and are
not publicly available. For the JAGES, all enquiries are to be addressed to the data
management committee via email: ​dataadmin.​ml@​jages.​net. All JAGES datasets
have ethical or legal restrictions for public deposition because of the inclusion ofsensitive information about the human participants. Regarding the ELSA, data are
available in an open-­access repository at https://www.​data-​archive.​ac.​uk/.
Supplemental material This content has been supplied by the author(s). It has
not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been
peer-­reviewed. Any opinions or recommendations discussed are solely thoseof the author(s) and are not endorsed by BMJ. BMJ disclaims all liability andresponsibility arising from any reliance placed on the content. Where the content
includes any translated material, BMJ does not warrant the accuracy and reliabilityof the translations (including but not limited to local regulations, clinical guidelines,
terminology, drug names and drug dosages), and is not responsible for any error
and/or omissions arising from translation and adaptation or otherwise.
Open access This is an open access article distributed in accordance with theCreative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits
others to copy, redistribute, remix, transform and build upon this work for any
purpose, provided the original work is properly cited, a link to the licence is given,and indication of whether changes were made. See: https://​creativecommons.​org/​
licenses/​by/​4.​0/.
ORCID iDs
Taiji Noguchi http://​orcid.​org/​0000-​0001-​9165-​5501
Masashige Saito http://​orcid.​org/​0000-​0002-​3997-​3884
Jun Aida http://​orcid.​org/​0000-​0002-​8405-​9872
Noriko Cable http://​orcid.​org/​0000-​0001-​5478-​1760
Taishi Tsuji http://​orcid.​org/​0000-​0002-​8408-​6619
Shihoko Koyama http://​orcid.​org/​0000-​0002-​7786-​4910
Takaaki Ikeda http://​orcid.​org/​0000-​0003-​4325-​4492
Ken Osaka http://​orcid.​org/​0000-​0001-​6885-​9514
Katsunori Kondo http://​orcid.​org/​0000-​0003-​0076-​816X

Funding This work was supported by a grant from the Grants-­in-­Aid for Scientific
Research (18KK0057, 19K24277) from the Japan Society for the Promotion of
Science. The English Longitudinal Study of Ageing was developed by a team ofresearchers based at the University College London, NatCen Social Research,and the Institute for Fiscal Studies. The data were collected by NatCen Social

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