In a multiple regression model, age (b =−0.068, P < 0.001), educa-tional levels (b = 0.350, P < 0.001), occupaeduca-tional status (b =−0.551, P = 0.001), the number of comorbidities (b = 0.119, P = 0.014), IADL (b =−0.352, P < 0.001), physical activity (b = 0.001, P = .029), nutri-tional management (b = 0.153, P = 0.002), participation in fraternal group activity (b = 0.178, P = 0.005) and religious activity (b = 0.166, P < 0.001), and contact with siblings and relatives through phone or letters (b = 0.150, P = 0.007) were found to contribute to the cogni-tive function of older adults living alone (Table 3). Conversely, annual income, the number of prescriptions, depression, activities of daily living, smoking, alcohol consumption, face-to-face contact with chil-dren, siblings, relatives and friends, and phone or letter contact with children and friends were not associated with the cognitive function of older adults living alone. These findings indicate that those who participated more frequently in fraternal group and religious activi-ties, and had more frequent contact with siblings and relatives through phone or letters, had better cognitive function on controlling age, educational level, employment, comorbidity, IADL, and nutri-tional management. The F test of the regression model was 70.99 (P < 0.001), and the explanatory power, adjusted R2, was 39.0.
4 | D I S C U S S I O N
Individual preferences, material resources to realize life preferences, and family systems have changed in the modern world. Inter-generational co-residence has consequently declined, and solitary liv-ing has increased among older adults worldwide, irrespective of differences among nations and cultural groups (Reher &
Requena, 2018). Social isolation and suicidal incidents are emerging social issues owing to the increase in the numbers of older adults liv-ing alone. Our findliv-ings have identified an important relationship between social participation and cognitive function in older people liv-ing alone.
Older adults living alone have been reported to have more health-related and psychosocial issues such as poverty and feelings of
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loneliness, compared with non-solitary older adults. Our findings dem-onstrate that compared with non-solitary older adults, those living alone participated more frequently in social interactions including reli-gious activities and face-to-face contact with friends. Conversely, they were less likely to be involved in other types of social participation including fraternal group activity, face-to-face contact with children, siblings and relatives, and phone or letter contact with siblings and rel-atives. This study only evaluated the frequency of social participation irrespective of the size or quality of the social network; therefore, it could not determine whether older adults living alone were at a higher
risk of decreased social participation. However, this study found that solitary older adults had lower educational levels and incomes, more comorbidities, more severe depression, poorer physical and cognitive function, less health promoting behaviours, and poorer nutritional sta-tus; previous studies had shown similar results. People living alone are more likely to be undernourished as they have been reported to be less likely to prepare sufficiently balanced meals (Sheean et al., 2018).
Several studies found that older adults living alone were likely to have difficulty in noticing new or worsening symptoms of disease or follow-ing directions for prescribed treatments (Sawyer, Armitage, Munro, T A B L E 1 Sample characteristics (N = 10 055)
Total sample n (%) or mean (SD)
Living alone n (%) or mean (SD) (n = 2410)
living with others n (%) or mean (SD)
(n = 7645) χ2ort (P)
Age in 2017 73.87 (6.54) 75.71 (6.77) 73.29 (6.35) 15.559 (<0.001)
Sex
Male 4278 (42.5%) 466 (19.3%) 3812(49.9%) 700.738 (<0.001)
Female 5777 (57.5%) 1945 (80.7%) 3832 (50.1%)
Educational level 7.19 (4.59) 5.57 (4.64) 7.70 (4.56) −20.188 (<0.001)
No education 2384 (23.7%) 966 (40.1%) 1418 (18.6%) 502.884 (<0.001)
Elementary school 3478 (34.3%) 757 (31.4%) 2691 (35.2%)
Middle and high school 3458 (34.4%) 567 (23.5%) 2891 (37.8%)
College~ 765 (7.6%) 121 (5.0%) 644 (8.4%)
Occupational status
Yes 3116 (31.0%) 592 (24.6%) 2524 (33.0%) 61.189 (<0.001)
No 6939 (69.0%) 1818 (75.4%) 5121 (67.0%)
Annual income (10 thousand KRW) (n = 10,053) 1186.21 (1403.71) 1082.58 (923.22) 1218.86 (1522.64) −5.316 (<0.001)
The number of comorbidities 2.72 (1.84) 3.19 (1.89) 2.58 (1.80) 14.337 (<0.001)
The number of prescriptions 3.89 (3.34) 4.41 (3.32) 3.73 (3.33) 8.844 (<0.001)
Depression 4.09 (4.08) 5.16 (4.41) 3.75 (3.92) 14.022 (<0.001)
Activities of daily living 7.14 (0.69) 7.13 (0.54) 7.14 (0.73) −0.315 (0.753)
Instrumental activities of daily living 10.88 (2.10) 11.10 (2.03) 10.81 (2.12) 6.026 (<0.001) Physical activity level (min/week) 184.68 (215.89) 162.63 (189.77) 191.63 (223.05) −6.263 (<0.001) Smoking
Yes 1028 (10.2) 215 (8.9) 813 (10.6) 5.860 (0.015)
No 9027 (89.8) 2195 (92.1) 6832 (89.4)
Alcohol consumption
Yes 2680 (26.7) 470 (19.5) 2210 (28.9) 82.921 (<0.001)
No 7375 (73.3) 1940 (80.5) 5435 (71.1)
Nutritional management 21.78 (1.62) 20.68 (1.67) 22.12 (1.44) −38.276 (<0.001)
Participation in fraternal group activity 1.03 (1.34) 0.71 (1.18) 1.13 (1.37) −14.565 (<0.001) Participation in religious activity 1.66 (2.0) 1.84 (2.07) 1.60 (1.98) 4.932 (<0.001) Face-to-face contact with children 3.18 (1.52) 2.99 (1.64) 3.23 (1.48) −6.556 (<0.001) Face-to-face contact siblings and relatives 1.42 (1.25) 1.30 (1.31) 1.45 (1.23) −4.991 (<0.001) Face-to-face contact with friends 4.74 (1.62) 4.99 (1.51) 4.66 (1.65) 9.164 (<0.001) Phone or letter contact with children 4.38 (1.57) 4.18 (1.81) 4.45 (1.47) −6.641 (0.320) Phone or letter contact with siblings and relatives 2.31 (1.49) 2.19 (1.57) 2.35 (1.46) −4.401 (<0.001) Phone or letter contact with friends 3.76 (1.95) 3.69 (2.08) 3.78 (1.91) −1.836 (0.66)
Cognitive function 25.22 (3.84) 24.34 (4.09) 25.49 (3.72) −12.325 (<0.001)
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TABLE2Correlationsbetweenmainvariables(N=2410) 234567891011 1.Agein2017−0.262**−0.126**0.120**0.098**0.130**0.151**0.373**−0.166**−0.130**−0.252** 2.Educationallevel10.325**−0.165**−0.130**−0.214**−0.089**−0.274**0.162**0.188**0.275** 3.Annualincome(10thousandKRW)(N=2049)0.325**1−0.124**−0.101**−0.227**−0.025−0.113**0.104**0.210**0.262** 4.Thenumberofcomorbidities−0.165**−0.124**10.661**0.337**0.168**0.247**−0.127**−0.401**−0.115** 5.Thenumberofprescriptions−0.130**−0.101**0.661**10.347**0.172**0.234**−0.132**−0.404**−0.132** 6.Depression−0.214**−0.227**0.337**0.347**10.178**0.321**−0.183**−0.485**−0.258** 7.Activitiesofdailyliving−0.089**−0.0250.168**0.172**0.178**10.556**−0.123**−0.178**−0.094** 8.Instrumentalactivitiesofdailyliving−0.274**−0.113**0.247**0.234**0.321**0.556**1−0.197**−0.258**−0.195** 9.Physicalactivitylevel(min/week)0.162**0.104**−0.127**−0.132**−0.183**−0.123**−0.197**10.168**0.164** 10.Nutritionalmanagement0.188**0.210**−0.401**−0.404**−0.485**−0.178**−0.258**0.168**10.208** 11.Participationinfraternalgroupactivity0.275**0.262**−0.115**−0.132**−0.258**−0.094**−0.195**0.164**0.208**1 12.Participationinreligiousactivity0.150**0.030−0.006−0.055**−0.142**−0.035−0.073**0.040*0.098**0.145** 13.Face-to-facecontactwithchildren−0.073**0.161**−0.031−0.051*−0.138**0.046*0.096**−0.0340.162**0.100** 14.Face-to-facecontactwithsiblingsandrelatives0.085**0.118**−0.022−0.084**−0.134**−0.066**−0.101**0.095**0.148**0.183** 15.Face-to-facecontactwithfriends−0.216**0.0100.013−0.017−0.168**−0.054**−0.0380.050*0.069**0.088** 16.Phoneorlettercontactwithchildren−0.072**0.187**−0.029−0.043*−0.179**0.0160.039−0.0380.188**0.110** 17.Phoneorlettercontactwithsiblingsandrelatives0.155**0.157**−0.038−0.077**−0.205**−0.057**−0.119**0.084**0.193**0.208** 18.Phoneorlettercontactwithfriends0.101**0.144**−0.068**−0.081**−0.301**−0.094**−0.188**0.105**0.229**0.258** 19.Cognitivefunction0.541**0.225**−0.120**−0.120**−0.239**−0.171**−0.377**0.182**0.225**0.273** *P<0.05. **P<0.01.
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TABLE2Continued 1213141516171819 1.Agein2017−0.0270.185**−0.170**0.073**0.181**−0.208**−0.117**−0.339** 2.Educationallevel0.150**−0.073**0.085**−0.216**−0.072**0.155**0.101**0.541** 3.Annualincome(10thousandKRW)(N=2049)0.0300.161**0.118**0.0100.187**0.157**0.144**0.225** 4.Thenumberofcomorbidities−0.006−0.031−0.0220.013−0.029−0.038−0.068**−0.120** 5.Thenumberofprescriptions−0.055**−0.051*−0.084**−0.017−0.043*−0.077**−0.081**−0.120** 6.Depression−0.142**−0.138**−0.134**−0.168**−0.179**−0.205**−0.301**−0.239** 7.Activitiesofdailyliving−0.0350.046*−0.066**−0.054**0.016−0.057**−0.094**−0.171** 8.Instrumentalactivitiesofdailyliving−0.073**0.096**−0.101**−0.0380.039−0.119**−0.188**−0.377** 9.Physicalactivitylevel(min/week)0.040*−0.0340.095**0.050*−0.0380.084**0.105**0.182** 10.Nutritionalmanagement0.098**0.162**0.148**0.069**0.188**0.193**0.229**0.225** 11.Participationinfraternalgroupactivity0.145**0.100**0.183**0.088**0.110**0.208**0.258**0.273** 12.Participationinreligiousactivity10.0210.0160.100**0.0200.098**0.117**0.177** 13.Face-to-facecontactwithchildren0.02110.050*0.124**0.756**0.077**0.101**−0.055** 14.Face-to-facecontactwithsiblingsandrelatives0.0160.050*10.068**0.076**0.619**0.121**0.120** 15.Face-to-facecontactwithfriends0.100**0.124**0.068**10.155**0.079**0.377**−0.080** 16.Phoneorlettercontactwithchildren0.0200.756**0.076**0.155**10.134**0.131**−0.049* 17.Phoneorlettercontactwithsiblingsandrelatives0.098**0.077**0.619**0.079**0.13**10.200**0.194** 18.Phoneorlettercontactwithfriends0.117**0.101**0.121**0.377**0.131**0.200**10.160** 19.Cognitivefunction0.177**−0.055**0.120**−0.080**−0.049*0.194**0.160**1 *P<0.05. **P<0.01.
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Singh, & Dawes, 2019; Uchmanowicz, Chudiak, Uchmanowicz, Rosinczuk, & Froelicher, 2018). Despite these challenges, most older people who live alone have been reported to have expressed a keen desire to maintain their independence (Wiles, Leibing, Guberman, Reeve, & Allen, 2011). In older adults, intact cognitive and physical function are essential requirements for maintaining an independent life (Aliberti et al., 2019). Therefore, management of cognitive func-tion and general health care for older people who live alone requires particular attention.
Factors relating to cognitive function in older people, such as age, educational level, employment status, comorbidities, physical function, and nutritional status were also found to be associated with the cog-nitive function of the older adults living alone in this study. The older adults living alone were more vulnerable to issues arising in relation to the factors mentioned previously. In addition, social group activity such as fraternal group and religious activities were also found to be related to cognitive function. This indicated that using cognitive skills through engaging in social activities may help maintain cognitive func-tion in later life; this may be explained through biological and psycho-social processes. Although there is insufficient evidence to show that intellectual and emotional stimulation prevents cognitive decline, they have been reported to protect cognitive function by boosting “cogni-tive reserve” (the brain's resilient ability to improvise and perform tasks despite damage); this is conferred by exposure to various activi-ties and social interactions (Belleville et al., 2011; Butler et al., 2018).
Social participation may reduce vulnerability to decline of cognitive function in older people by enhancing efficient use of the neuronal network. In addition, some studies have identified the positive effects of social engagement on psychological health that lead to lower levels of depression and distress (Amagasa et al., 2017; Roh et al., 2015).
Social participation may provide individuals with social roles, emo-tional support, and self-esteem that guard against depression and reduce the stress response, which may mitigate changes in associated hormones and neuropathology (Amagasa et al., 2017; Pillai &
Verghese, 2009).
Considering the effects of social participation, it is necessary to develop appropriate interventions for older adults and provide them with more opportunities for cognitive stimulation through various social activities. Several studies have examined the effect of exercise or cognitive activities on social interaction on cognitive function (Iizuka et al., 2019; Rektorova et al., 2019). However, isolating social factors for analysis was not feasible; therefore, social engagement includes physical and cognitive aspects in addition to social relation-ships. Various forms of social activity, for example, folk dancing and playing card games, include physical, social, and cognitive elements that stimulate the cognitive process. A study evaluating the impact of board games on cognitive function found that the effect size of the group playing games with other people was greater than that of the group playing games alone using tablets (Iizuka et al., 2019). According to Piccirilli and colleagues (2019), a positive effect on cognitive T A B L E 3 The association of cognitive function and related variables among older adults who live alone (N = 2410)
Variables B SE β t P
Age in 2017 −0.068 0.011 −0.112 −5.896 <0.001
Sex −0.333 0.206 −0.032 −1.612 0.107
Educational level 0.350 0.018 0.397 19.765 <0.001
Occupational status −0.551 0.162 −0.058 −3.413 0.001
Annual income (10 thousand KRW) (N = 2049) <0.001 0.000 0.016 0.876 0.381
The number of comorbidities 0.119 0.048 0.055 2.457 0.014
The number of prescriptions 0.010 0.027 0.008 0.356 0.722
Depression −0.016 0.019 −0.018 −0.884 0.377
Activities of daily living 0.041 0.145 0.005 0.280 0.779
Instrumental activities of daily living −0.352 0.044 −0.174 −8.009 <0.001
Physical activity level (min/week) 0.001 0.000 0.037 2.187 0.029
Smoking 0.194 0.250 0.013 0.775 0.438
Alcohol consumption 0.075 0.182 0.007 0.412 0.680
Nutritional management 0.153 0.049 0.062 3.115 0.002
Participation in fraternal group activity 0.178 0.063 0.052 2.842 0.005
Participation in religious activity 0.166 0.034 0.084 4.949 <0.001
Face-to-face contact with children 0.041 0.062 0.016 0.664 0.507
Face-to-face contact with siblings and relatives −0.046 0.064 −0.015 −0.714 0.475
Face-to-face contact with friends −0.083 0.050 −0.031 −1.676 0.094
Phone or letter contact with children −0.062 0.057 −0.028 −1.094 0.274
Phone or letter contact with siblings and relatives 0.150 0.055 0.058 2.705 0.007
Phone or letter contact with friends 0.060 0.036 0.030 1.643 0.100
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function could be anticipated through integrative activities that incor-porate physical, mental, and social elements. Synergies involving physical, cognitive, and social factors may result in significant out-comes, such as an improvement in cognitive function. In addition, the effects of social participation are also not limited to cognitive func-tion. A Chinese study demonstrated that in older people living alone, those who participated in more social activities had better physical function and lower risks of mortality (Gu, Feng, & Yeung, 2018).
Therefore, social participation may be an important modifiable factor for maintaining overall health and independence of older adults living alone.
For almost all variables, excluding face-to-face contact with fri-ends, the older adults living with others had more frequent social con-tact than those who lived alone. Multiple regression analyses showed no significant relationship between social contact (except for phone or letter contact with siblings and relatives) and cognitive function when controlling other factors. Several previous studies showed inconsistent association between levels of contact and cognition among older adults. Kim and Chon (2018) reported that cognitive decline was not associated with the frequency of face-to-face contact with a first-born child; however, it was associated with contact through phone calls, letters, and emails. Another community-based longitudinal study reported that frequent phone or letter contact with children was negatively related to cognitive decline; conversely, fre-quent face-to-face contact with children was positively related to cog-nitive decline in older adults (Lee & Kim, 2016). Lee and Kim (2016) explained these contradictory results may be attributed to the stress of supporting their adult children in home-based commitments. In many Asian cultures involving family interdependence, adult children may ask for their parents' help in the house or for childcare; many older adults often provide their adult children with these forms of support. The physical and mental burden on older adults in these situ-ations may generate stress, which could result in neuronal degenera-tion and cognitive decline. It is also plausible that frequent face-to-face contact with adult children implies a need to receive aid from them owing to age-related functional dependence and chronic dis-ease. Several studies have shown inconsistent results; therefore, fur-ther studies are needed to identify plausible relationships between social contact and cognitive function.