Previous research has demonstrated links between such unhealthy behaviors and the risk of such adverse consequences as obesity, diabetes, cancer, stroke, and sudden cardiac death, the researchers noted.
But it has not been clear what effect they might have on the risk of disability," they added.
To find out, they turned to the French Three-City study, which enrolled community-living people 65 and older in Dijon, Bordeaux, and Montpelier. Follow-up was common for the first 6 years of the study, but after that each center had different aims; in the Dijon cohort, investigators were interested in physical function and disability.
Participants were recruited from electoral rolls in 1999, 2000, and 2001, and were free of disability at the time. Investigators interviewed them about lifestyle factors when they enrolled, and disability was assessed by an in-person interview six times over 12 years -- at baseline and after 2, 4, 7, 9, and 11 years in the study.
Elbaz and colleagues used three disability scales -- mobility, instrumental activities of daily living, and basic activities of daily living -- and constructed a hierarchical indicator of disability that combined the three.
In other words, a participant could be fully independent -- able to function without help on all scales -- or need help on one, two, or three of the domains.
Low or intermediate physical activity, consumption of fruit and vegetables less than once a day, current smoking or having quit less than 15 years before, and either heavy or no consumption of alcohol were all considered unhealthy behaviors.
All told, Elbaz and colleagues had complete data on 3,982 people who contributed 27,141 person-years in a total follow-up of 12 years; 1,236 developed a disability, for an incidence of 45.5 per 1,000 person-years.
In survival analyses, adjusted for age, sex, marital status, and education, low or intermediate physical activity was associated with a 72% increase in the risk of disability.
An unhealthy diet -- consuming fruit and vegetables less than once a day -- was associated with a 24% increase in the hazard, while current smoking or having quit less than 15 years before entering the study was associated with a 26% increase in the chance of disability.
In one model of unhealthy behaviors, former drinkers had a 49% higher risk of disability than light to moderate drinkers, but in the final model only inactivity, diet, and smoking remained significant.
The risk of disability increased significantly (at P<0.001) with the number of unhealthy behaviors, and participants with three unhealthy behaviors had a 2.53-fold increased hazard of disability compared with those with none, Elbaz and colleagues reported.
To test for reverse causation, the researcher repeated the analysis excluding people who developed disability in the first 4 years of the study; the results were similar to the overall analysis, Elbaz and colleagues found.
The investigators cautioned that disability was self-reported in interviews and the main analyses did not take into account recovery from disability. In addition, they noted, behavior was assessed at the start of the study but not later.
And, they added, people who took part in the study were community-living, well-functioning adults at the beginning and might have been in better health than nonparticipants.
The study had support from the Institut National de la Santé et de la Recherche Médicale, the Victor Segalen-Bordeaux II University, the Sanofi-Synthélabo Company, the Fondation pour la Recherche Médicale, the Caisse Nationale Maladie des Travailleurs Salariés, the Direction Générale de la Santé, Conseils Régionaux of Bourgogne, the Fondation de France, the Ministry of Research-INSERM Program, the Mutuelle Générale de l'Education Nationale, the Institut de la Longévité, the Conseil Général de la Côte d'or, the Fondation Plan Alzheimer, and the Institut national de prévention et d'éducation pour la santé.
Elbaz did not report any potential conflicts.