Association between lifestyle factors and the incidence of multimorbidity in an older English population.

Background: Evidence on the role of lifestyle factors in relation to multimorbidity, especially in elderly populations, is scarce. We assessed the association between five lifestyle factors and incident multimorbidity (presence of ≥2 chronic conditions) in an English cohort aged ≥50 years. Methods: We used data from wave 4, 5 and 6 of the English Longitudinal Study of Ageing. Data on smoking, alcohol consumption, physical activity, fruit and vegetable consumption and BMI were extracted and combined to generate a sum of unhealthy lifestyle factors for each individual. We examined whether these lifestyle factors individually or in combination predicted during the subsequent wave. We used marginal structural Cox proportional hazard models, adjusted for both time-constant and time-varying factors. Results: A total of 5,476 participants contributed 232,749 person-months of follow-up during which 1,156 cases of incident multimorbidity were recorded. Physical inactivity increased the risk of multimorbidity by 33% (adjusted Hazard Ratio (aHR) 1.33, 95% CI 1.03-1.73). The risk was about two-three times higher when inactivity was combined with obesity (aHR 2.87, 95% CI 1.55-5.31) or smoking (aHR 2.35, 95% CI 1.36-4.08) and about four times when combined with both (aHR 3.98, 95% CI 1.02-17.00). Any combination of 2, 3 and 4 or more unhealthy lifestyle factors significantly increased the multimorbidity hazard, compared to none, from 42% to 114%. Conclusion: This study provides evidence of a temporal association between combinations of different unhealthy lifestyle factors with multimorbidity. Population level interventions should include reinforcing positive lifestyle changes in the population to reduce the risk of developing multimorbidity.