Abstract
BACKGROUND: There is no safe lower limit for alcohol intake, and even small amounts increase the risk of premature mortality. It is not known whether a change in cardiorespiratory fitness can modify the association between a change in alcohol intake and mortality. METHODS: We analysed data of the healthy adults from the second (HUNT2; 1995-7) and third (HUNT3; 2006-8) surveys of the population-based Trøndelag Health Study, Norway. Alcohol intake at HUNT2 and HUNT3 was divided into three groups: abstainers, within recommendations (≤ 140 g/week for men, ≤ 70 g/week for women) or above recommendations (> 140 g/week for men, > 70 g/week for women). Using a validated non-exercise prediction equation, we classified participants into two sex- and age-specific fitness groups (unfit: 20% least fit; fit: 80% most fit) at both HUNT2 and HUNT3. Using multi-variable-adjusted Cox analyses, adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) were estimated for an association between all-cause mortality and a change in alcohol and fitness status. RESULTS: A total of 24,853 healthy adults (mean [standard deviation] age, 54.7 [12] years; 54.1% women) were included. Over a median follow-up of 16.6 (interquartile range, 16.2-17.1) years, 3921 participants died. Increased alcohol intake from HUNT2 to HUNT3 was associated with an increased risk of mortality. Alcohol abstainers who reported to drink within the recommendations 10 years later (aHR, 1.20; 95% CI 1.00-1.44), and drinkers who increased their intake from within the recommendations at HUNT2 to above at HUNT3 (aHR, 1.25; 95% CI 0.99-1.57) had an increased risk of mortality, compared with the persistent abstainers. Participants drinking within the recommendations at HUNT2 but abstained from drinking at HUNT3 were not at a higher risk of mortality (aHR, 1.14; 95% CI 0.80-1.62). A change in fitness modified the relationship between alcohol intake and all-cause mortality (P = 0.03), and participants who remained unfit had higher mortality risks. Compared with the reference group who abstained from alcohol and remained fit from HUNT2 to HUNT3, those who remained unfit and persistently abstained, started drinking or consistently drank alcohol within the recommended limits had aHRs of 1.65 (95% CI 1.19-2.30), 1.46 (95% CI 1.04-2.06) and 1.68 (95% CI 1.36-2.08), respectively. For participants who remained fit, the mortality risk associated with changes in alcohol intake was not higher than for the reference group, except for those who started drinking [aHR, 1.32 (195% CI 04-1.68)]. Compared with peers remaining fit, decreasing fitness increased the mortality risk among persistent abstainers and consistent drinkers. CONCLUSIONS: Increased alcohol intake over the years was associated with an increased risk of mortality. A change in cardiorespiratory fitness was a better predictor of mortality, and maintaining fitness above the lowest 20% for one's age and sex attenuated the association between a change in alcohol intake and all-cause mortality.