Alcohol use of non-high risk and high risk drinkers
Figure 1 shows the changes in abstainers, non-high risk drinkers and high risk drinkers from 2001 and 2013. The prevalence of abstainers significantly decreased between 2001 and 2004 (F (1, 54 985) = 5.74, p = .02), from 16.2 % (95 % CI: 15.7–16.7 %) to 15.3 % (95 % CI: 14.8–15.8 %), and has increased steadily since 2004. The rate of abstinence in 2013 (20.2 %; 95 % CI: 19.6–21.0 %) was significantly higher than in 2004, F (1, 51 909) = 149.0, p < .001. The prevalence of high risk drinkers significantly increased between 2001 (18.8 %; 95 % CI: 18.2–19.3 %) and 2004 (20.2 %; 95 % CI: 19.6–20.8 %), F (1, 54 504) = 12.09, p = .001; remained fairly stable between 2004 and 2010 (19.5 %; 95 % CI: 18.9–20.1 %) with no significant changes in prevalence; and then decreased significantly from 2010 to 2013 (17.6 %; 95 % CI: 17.1–18.2 %), F (1, 47 999) = 18.77, p < .001. The prevalence of non-high risk drinkers decreased significantly from 64.5 % (95 % CI: 63.78–65.16 %) in 2001 to 60.9 % (95 % CI: 60.2–61.6 %) in 2010, F (1, 52 127) = 48.28, p < .001, and remained stable between 2010 and 2013 (61.2 %; 95 % CI: 60.4–62.0 %).
The average consumption of non-high risk drinkers increased from 2.57 L (95 % CI: 2.53–2.62 L) a year in 2001 to 2.92 L (95 % CI: 2.87–2.94 L) in 2004, t = 10.39, p < .001, and decreased steadily to 2.80 L (95 % CI: 2.74–2.85 L) in 2013, t = 3.49, p < .001 (see Fig. 2). The average consumption of high-risk drinkers increased from 20.71 L (95 % CI: 20.22–21.20 L) in 2001 and peaked at 21.52 L (95 % CI: 21.02–22.01 L) in 2010, t = 2.29, p = .02. Although, the decrease in consumption from 2010 to 2013 (21.03 L; 95 % CI: 20.51–21.55 L) was non-statistically significant, t = 1.34, p = .181, the average consumption of high risk drinkers in 2013 was not significantly different from the average consumption in 2001, t = 0.88, p = .380, suggesting that the consumption level has returned to the 2001 level.
Alcohol use of non-frequent and frequent heavy episodic drinkers
The changes in prevalence of frequent heavy episodic drinkers and non-frequent heavy episodic drinkers are shown in Fig. 3. The prevalence of frequent heavy episodic drinkers decreased steadily from 27.7 % (95 % CI: 27.1–28.4 %) in 2001 to 24.91 % (95 % CI: 24.2–25.6 %) 2013, F (1, 49001) = 32.72, p < .001. The prevalence of non-frequent heavy episodic drinkers increased significantly from 55.9 % (95 % CI: 55.1–56.6 %) in 2001 to 57.6 % (95 % CI: 56.7–58.3 %) in 2004, F (1, 54565) = 11.11, p < .001, and decreased to 54.2 % (95 % CI: 53.4–54.9 %) in 2013, F (1, 51293) = 40.78, p < .001.
Figure 4 shows the changes in average yearly consumption for frequent heavy episodic drinkers and the number of days of heavy episodic drinking. Both the number of days of heavy drinking and overall yearly consumptions increased significantly from 2001, peaked at 2007 (p < .001) and dropped significantly in 2013 (p < .05). The number of days of heavy episodic drinking was still significantly higher in 2013 (97.8 days; 95 % CI: 94.4–101.3 days) than in 2001 (92.4 days; 95 % CI: 89.4–95.5 days) despite its recent drop, t = 2.31, p = .021, but the yearly consumption in 2013 (15.59 L; 95 % CI: 15.14–16.04 L) was no longer significantly higher than in 2001 (15.13 L; 95 % CI: 14.72–15.53 L), t = 1.49, p = .135.
Trends in treatment seeking
The overall treatment rate increased from 335 per 100,000 population in 2002 to 438 per 100,000 population in 2007, and then decreased to 392 per 100,000 (Fig. 5). The treatment rate by birth cohorts and age groups were shown in Fig. 6. The treatment rates decreased steadily for the two oldest cohorts (1950–1959 and 1940–1949). There was no obvious trend for the 1960–1969 cohort, with the treatment rate varying between 441 and 512 per 100,000 population between 2002 and 2013. This rate increased for the younger cohorts from 2002 but peaked at different times. For the 1970–1979 cohort, the treatment rate increased between 2002 (420 per 100,000 population) and 2007 (591 per 100,000 population), and this increase levelled off after 2007; for the 1980–1989 cohort, this rate increased rapidly between 2002 and 2007 from 213 per 100,000 population to 490 per 100,000 population, and then dropped from 2009 to 2013 (424 per 100,000 population); for the 1990–1999 cohort, the treatment rate increased from 2002 (1.97 per 100,000 population) and peak at 2010 (314 per 100,000 population), and remained stable between 2010 and 2013 (298 per 100,000 population). Analyses by age groups also showed decrease in treatment episodes in all age groups in 2013 (Fig. 7).