Table 1 Summary of the characteristics of included articles
No. | General information | Study characteristics | Participant characteristics | Outcomes of interest | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Author/Year | Country | Region | Economic status | Study design | Sample size | Loneliness assessment tools used | No. of scale items | Interpretations | % of Women | Age (year) | DM duration (year) | Type of DM | Prevalence | Risk factors | Types of risk factors | |
1 | Akhter-Khan, 2021 [36] | USA | Americas | HI | Cohort | 204 | One item from the CES-D | 1 | Four response categories: No, transient (lonely at visit 1), incident (lonely at visit 2), and persistent loneliness | NI | NI | NI | NI | ✔ |  |  |
2 | Chao, 2022 [28] | USA | Americas | HI | Cohort | 2829 | 3i UCLA Loneliness Scale | 3 | Cutoff for loneliness ≥ 6 | 63.2 | 75.6 (6.0) | NI | Type 2 diabetes | ✔ | ✔ | Demographic factors (age, sex, and ethnicity), health-related factors (multimorbidity and BMI), and social factors (previous experience of loneliness) |
3 | Durmus, 2022 [17] | Turkey | Europe | UMI | Cross-sectional | 500 | 20i UCLA Loneliness Scale | 20 | Higher scores indicated a higher level of loneliness | 49.4 | 49.64 (16.79) | 2.36 (1.13) | Type 1 diabetes, Type 2 diabetes | ✔ | ✔ | Demographic factors (age, sex, marital status, employment status, education level, and economic status) and health-related factors (duration of diabetes) |
4 | Hackett, 2020 [5] | The United Kingdom | European | HI | Longitudinal | 264 | 3i Revised UCLA Loneliness Scale | 3 | The average scores ranged from 1 to 3, with higher scores indicating a higher level of loneliness | 45.8 | 64.62 (8.46) | NI | Type 2 diabetes | ✔ | ✔ | Demographic factors (age, sex, and economic status), health-related factors (HbA1c level), social factors (living alone and social isolation), and psychological factor (depression) |
5 | Kobos, 2021 [20] | Poland | European | HI | Cross-sectional | 250 | 20i Revised UCLA Loneliness Scale | 20 | Scores of 20–34, 35–49, 50–64, and 65–80 indicate a low, moderate, moderately high, and high degree of loneliness, respectively | 46.4 | 57.93 (17.43) | 12.15 (9.55) | Type 1 diabetes, Type 2 diabetes | ✔ | ✔ | Demographic factors (age, sex, marital status, and education level) |
6 | Pengpid, 2023 [37] | Thailand | South-East Asian | UMI | Longitudinal | 557 | One item from the CES-D | 1 | Three responses: very rarely or none, often or sometimes, and almost always. Data are categorized as incident (lonely in 2017 but not in 2015) and persistent loneliness (lonely in both 2015 and 2017) | NI | NI | NI | NI | ✔ |  |  |
7 | Shibata, 2021 [38] | Japan | Western Pacific | HI | Longitudinal | 273 | 6i DJG Loneliness Scale | 6 | A score of ≥ 1 indicates the presence of loneliness | NI | NI | NI | NI | ✔ |  |  |
8 | Stessman, 2014 [39] | Israel | European | HI | Cohort | 253 | Single subjective assessment | 1 | Four responses: never, rarely, often, and very often. The data were classified as dichotomous (not lonely vs. lonely) | NI | NI | NI | NI | ✔ |  |  |
9 | Tomida, 2023 [40] | Japan | Western Pacific | HI | Cohort | 649 | 20i Revised UCLA Loneliness Scale v3 | 20 | Cutoff for loneliness ≥ 44 | 40.1 | 74 (5.5) | NI | Type 1 diabetes, Type 2 diabetes, other types of diabetes | ✔ | ✔ | Demographic factors (age, sex, employment status, and education level), health-related factor (cognitive function), social factor (living alone), and psychological factor (depression) |
10 | Yousefzadeh, 2021 [41] | Iran | Eastern Mediterranean | LMI | Cross-sectional | 257 | 20i Revised UCLA Loneliness Scale | 20 | Higher scores indicated a higher level of loneliness | 55.3 | NI | NI | Type 2 diabetes | ✔ |  |  |