Social isolation and its psychosocial factors in mild lockdown for the COVID-19 pandemic: a cross-sectional survey of the Japanese population

<jats:sec><jats:title>Objective</jats:title><jats:p>This study investigated the sociodemographic, behavioural and psychological characteristics of socially isolated individuals during the ‘mild lockdown’ period of COVID-19 in Japan.</jats:p></jats:sec><jats:sec><jats:title>Design</jats:title><jats:p>A cross-sectional study.</jats:p></jats:sec><jats:sec><jats:title>Setting</jats:title><jats:p>The seven prefectures where the emergency declaration was first applied in Japan.</jats:p></jats:sec><jats:sec><jats:title>Participants</jats:title><jats:p>We collected data on 11 333 individuals (52.4% women, 46.3±14.6 years) living in the seven prefectures where the emergency declaration was first applied. The online survey was performed between 11 May and 12 May 2020, in the final phase of the state of emergency.</jats:p></jats:sec><jats:sec><jats:title>Primary outcome measures</jats:title><jats:p>Lubben Social Network Scale (LSNS-6)</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>We found that male sex (95% CI 1.60 to 1.98), middle age (95% CI 1.55 to 1.93) and lower income (eg, annual household income <2.0 million: 95% CI 2.29 to 3.54) predicted social isolation; being a student was a protective factor against social isolation (95% CI 0.26 to 0.62). In the comparisons of each item of the LSNS-6 by sociodemographic characteristics, men were more likely to have fewer people to talk to about their personal problems (95% CI −0.37 to −0.28) and to seek help from (95% CI −0.39 to −0.30), and the middle-aged group had a lower social network of friends. Additionally, social isolation was associated with decreased online interaction with familiar people (95% CI −1.28 to −1.13) and decreased optimistic thinking under mild lockdown (95% CI −0.97 to −0.86).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>We identified the sociodemographic and psychological characteristics associated with social isolation under mild lockdown. These results are expected to be a useful resource for identifying which groups may require intervention to improve their social interactions in order to preserve their mental health during the pandemic.</jats:p></jats:sec>