We included 5100 participants in the study. The mean age of participants was similar to that of the 1499 people excluded from our analysis because of missing data on health outcomes (51.3 v. 51.4 yr, p = 0.50) (). However, the analytic sample comprised fewer women (29.5% v. 38.6%, p < 0.001) and more participants with healthy behaviours other than smoking ().
Baseline characteristics of participants included in the analysis in comparison with those excluded because of missing data on health outcomes
Among participants, 549 died during follow-up, and 953 met the criteria for successful aging at the end of follow-up. Compared with the normally aging group, participants in the successfully aging group were younger (mean age 49.7 [standard deviation (SD) 4.9] v. 51.3 [SD 5.3] yr), and were more likely to be married (81.2% v. 77.8%) and have a university education or higher (31.6% v. 24.2%) (t test for continuous variables, χ2 test for categorical variables, all p < 0.001) ().
Comparison of characteristics between participants in the successful and normal aging groups
shows the association of each healthy behaviour with successful aging and staying alive for the duration of follow-up (i.e., survival). Because there was no interaction between healthy behaviours and sex (data not shown, Wald test, all p > 0.17), we combined men and women in the analysis. Compared with former and current smokers, participants who had never smoked had 1.3 times greater odds of meeting the criteria for successful aging (OR 1.29, 95% confidence interval [CI] 1.11–1.49; PAR 12.4%) and 1.5 times greater odds of survival (OR 1.53, 95% CI 1.27–1.85; PAR 20.6%) (). Compared with no and heavy alcohol consumption, moderate consumption was associated with greater odds of successful aging (OR 1.31, 95% CI 1.12–1.53; PAR = 16.6%) and survival (OR 1.40, 95% CI 1.16–1.68; PAR 20.4%) (). Compared with inactive participants, participants who were physically active were more likely to meet the criteria for successful aging (OR 1.45, 95% CI 1.25–1.68; PAR = 18.7%) and to be alive at the end of follow-up (OR 1.32, 95% CI 1.10–1.60; PAR 14.0%) (). Finally, consuming fruits and vegetables daily was associated with greater odds of successful aging (OR 1.35, 95% CI 1.15–1.58; PAR 18.1%) and survival (OR 1.33, 95% CI 1.10–1.60; PAR 17.2%) ().
Association between healthy behaviours, successful aging and survival to end of follow-up among 5100 participants
In our study population, 4.9% of the participants engaged in no healthy behaviours (score = 0), 18.3% engaged in 1 (score = 1), 33.8% engaged in 2 (score = 2), 31.3% engaged in 3 (score = 3), and 11.8% engaged in 4 (score = 4) (data not shown). The mean change in score 5 years later was small for both the normally aging group (0.08 ± 0.95) and the successfully aging group (0.00 ± 0.95) (data not shown). By the end of follow-up, the mean score for healthy behaviours had increased in both groups (0.10 ± 1.00 for the normally aging group; 0.17 ± 0.95 for the successfully aging group) (data not shown). The correlation between repeated measurements of the score was 0.58 (Spearman correlation, p < 0.001, n = 4381) at 5 years’ follow-up and 0.53 (Spearman correlation, p < 0.001, n = 4186) at the final follow-up (data not shown).
Compared with participants who engaged in no healthy behaviours at baseline, participants who engaged in 2 or more healthy behaviours had greater odds of successful aging and survival (). The OR for having at least 1 healthy behaviour was 1.92 for successful aging (PAR 46.6%) and 2.32 for being alive at the end of follow-up (PAR 55.6%) (). The benefit of healthy behaviours appeared to increase linearly (Wald test, p < 0.001): when the score for healthy behaviours was entered in the logistic model as a continuous variable, the OR per 1 additional healthy behaviour was 1.33 (95% CI 1.24–1.43) for successful aging and 1.39 (95% CI 1.27–1.52) for survival.
Figure 2: Association between the number of healthy behaviours participants showed at baseline and (A) successful aging or (B) survival. In model 1, each number of healthy behaviours is included in the model as a category, and ORs are calculated with “0 (more ...)
As the number of healthy behaviours increased, so did the odds of absence of disability; good lung, cognitive and physical functioning; and mental health (, all p
for trend < 0.001; Appendix 3, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.121080/-/DC1
). We saw no corresponding association for systolic blood pressure before taking into account antihypertensive drugs; repeating the analysis using medication data and good systolic blood pressure to define good functioning showed a clear association with the number of healthy behaviours (p
for trend < 0.001).
Associations between the number of healthy behaviours and measures of functioning used to define successful aging
Our sensitivity analyses showed that excluding deaths from the main analysis did not change the association between healthy behaviours and successful aging (OR per 1 additional healthy behaviour was 1.29, 95% CI 1.20–1.38; Appendix 4, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.121080/-/DC1
). We found similar results when alternative cut-offs for good mental health were used (OR per 1 additional healthy behaviour 1.37, 95% CI 1.27–1.47; Appendix 5, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.121080/-/DC1
). In addition, the results were little changed with inverse probability weighting to account for missing data (OR per 1 additional healthy behaviour 1.35, 95% CI 1.25–1.45 for successful aging; OR 1.40, 95% CI 1.29–1.53 for survival; Appendix 6, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.121080/-/DC1