Data source and study population
We conducted a cross-sectional study using the data from the Japan COVID-19 and Society Internet Survey (JACSIS), a large Internet-based cohort study. The first survey, conducted from August to September 2020, examined how the COVID-19 pandemic affected people’s daily lives in Japan. Using simple random sampling, the survey requests were sent by the research agency to the panelists, who were each selected by sex, age, and prefecture. The panelists who consented to participate accessed the designated website and responded to the survey. At any point, they had the option of not responding to any part of the survey or discontinuing it altogether. The survey was closed when the target number of respondents for each sex, age, and prefecture were met. Overall, the participation rate for the survey was 12.5% (28,000 out of 224,389).
Management of data quality and generating the study population
To validate the data quality, we excluded the respondents with discrepancies and/or artificial/unnatural responses. In this regard, three items were used to detect any discrepancies: (1) “Please choose the second from the bottom”; (2) choosing positive in all questions (nearly 10 or more) for using 9 drugs including illegal drugs; and (3) choosing positive in the questions for having 16 chronic diseases. In total, 2,518 respondents were excluded, leaving the remaining 25,482.
Specifically, alcohol drinkers were identified by the question “Are you currently drinking alcohol?” Those who responded “Never,” “Had once or more in the past, but do not regularly drink,” and “Used to regularly drink, but not now” were excluded from the study as non-drinkers. The respondents who answered “Sometimes” and “Most days” were identified as current drinkers. In addition, the population in this study was limited to 20 years of age and over, which is the legal age for drinking in Japan. Overall, 12,067 participants were categorized as current drinkers.
This study used questions regarding: (1) alcohol use as explanatory variables; (2) behaviors under the first COVID-19 emergency declaration in Japan, as outcome variables; and (3) demographics and potential health factor-related alcohol use.
Drinkers were categorized by using the series of Cut, Annoyed, Guilty, Eye-opener (CAGE) questions, a validated tool for identifying a person who potentially abuses alcohol or suffers from alcohol use disorder. Specifically, this tool consists of the following four items in which a score of 1 is given for each positive response: (1) “Have you ever felt you needed to cut down on your drinking?”; (2) “Have people annoyed you by criticizing your drinking?”; (3) “Have you ever felt guilty about drinking?”; and (4) “Have you ever felt you needed a drink first thing in the morning (eye-opener) to steady your nerves or to get rid of a hangover?”. The respondents were asked, “How many of these items did you have after March 2020?” The recommended cutoff for CAGE is 2 or more, and a score of 4 indicated potential alcohol use disorder, while that of 2 to 3 indicated potential alcohol abuse in primary care.
The high-risk taking behaviors against the stay-at-home policy were identified by the question “From April to May 2020, how often did you perform the following behaviors?” We focused on April to May 2020, which was the first emergency declaration for COVID-19 in Japan. The frequency of such behaviors was categorized into two aspects: never, and onece or more. Additionally, the following 18 activities were used as a measurement of such behaviors: visiting friends; visiting relatives; inviting people at home; dining out at restaurants; dining out at izakayas (Japanese style dining bars) or bars; going to a night club; going to karaoke; going to a music club; participating in sports events; going out to watch sports events; going to a gym; going to gamble; going to a hostess bar; going to a brothel; riding on a crowded train; going to a museum/theater; participating in local events; and going shopping for unnecessary items. All of these activities were limited under the first emergency declaration because they were related to the clusters of COVID-19 before March 2020 or they have higher risk of gathering at one place.
Demographics and potential health factors related to alcohol use
The demographic questions included the following: age, sex, educational level, marital status, annual household income, current living situation, and job. Educational level was categorized into three aspects: low (graduated from high school or less), middle (graduated from vocational or junior college), and high (graduated from university or more). Marital status was categorized into three aspects: married, single, and divorced/widowed. Equivalent annual household income, which is divided household income by the square root of the number of household members, was categorized into six aspects: under 2 million yen, 2–4 million yen, 4–6 million yen, 6–10 million yen, 10 million yen or more, and do not know/do not want to answer. Current living situation identified whether the participant either lived with someone or lived alone, while job was categorized into seven aspects: executive to manager, regular employee, self-employed, non-regular employee, no job (as a student or retiree), only housework, and unemployed. Finally, the potential factors related to alcohol use included: current smokers, sleep duration of less than six hours, depression (history or current), and other mental illnesses (history or current).
The statistical analyses were performed using Stata 15 software. The means and standard deviations (SD) were presented as continuous variables, while the categorical variables were presented as proportions. First, we determined the p for the difference of the means and proportions of demographics, and the potential health factors according to the CAGE scores in each category. Second, multivariable binary logistic regression models were used to analyze the association between the categories of CAGE scores and the presence (or absence) of each of the 18 behaviors during the first COVID-19 emergency declaration. In this regard, Model 1 was a cured model, while Model 2 was adjusted for the demographics and potential health factors related to alcohol use. Finally, the adjusted odds ratios (aOR) and 95% confidence intervals (CI) for each of the 18 behaviors were reported. The statistical tests were two-sided, and the value of p < 0.05 was considered statistically significant.
All procedures were conducted in accordance with the ethical standards of the Helsinki Declaration of 1975 (revised in 2013). The study protocol was reviewed and approved by the Research Ethics Committee of the Osaka International Cancer Institute (approved on June 19, 2020; Approval No. 20084). In addition, the Internet survey agency respected the Act on the Protection of Personal Information in Japan. All participants provided their informed consent before responding to the online questionnaire. As an incentive, credit points (known as “E-points”), which could be used for Internet shopping and cash conversion, were provided to the participants.