The long-term effect of a population-based lifestyle intervention on smoking and alcohol consumption. The Inter99 Study - a randomized controlled trial

AIMS: To examine whether improvements in smoking and alcohol consumption throughout the five-year course of a population-based multi-factorial lifestyle intervention were sustained five years after its discontinuation.

DESIGN: Population-based randomized controlled trial.

SETTING: Suburbs of Copenhagen, Denmark.

PARTICIPANTS: 9,415 people aged 30 to 60 years were randomized to an intervention group (n = 6,091) and an assessment only control group (n = 3,324).

INTERVENTION: All participants in the intervention group received screening, risk assessment, and individual lifestyle counseling; participants at high risk of ischemic heart disease - according to pre-specified criteria - were also offered group-based counseling.

MEASUREMENTS: Self-reported point abstinence from smoking as well as changes in the average alcohol consumption per week and binge drinking in the past week from baseline to ten-year follow-up were investigated using random-effects modeling.

FINDINGS: At ten-year follow up, persons in the intervention group reported a higher smoking abstinence rate (OR = 1.84, CI95% : 1.02-3.33, p = 0.043) and a greater reduction in binge drinking (net change = -0.08 days with binge drinking in the last week, CI95% : -0.16 to -0.01, p = 0.028) than in the control group. There were no detectable long-term intervention effects on the average alcohol consumption per week.

CONCLUSIONS: A population-based multi-factorial lifestyle intervention of five years' duration in Denmark had sustained beneficial effects on smoking abstinence and binge drinking five years after its discontinuation.