Changes in leisure time physical activity and subsequent disability retirement: A register-linked cohort study.BACKGROUND
 Disability retirement is an economic, public health and work life issue causing costs for employees, workplaces and society.  Adopting physical activity at middle-age has been associated with reduced risk of sickness absence and mortality.  The aim of this study was to examine how changes over time in leisure time physical activity are associated with subsequent disability retirement among midlife employees.


 The Helsinki Health Study cohort baseline (phase 1) mail questionnaire survey data were collected in 2000, 2001 and 2002 among 40-60-year-old employees of the City of Helsinki, Finland.  A phase 2 survey was conducted in 2007 (N = 3943).  Respondents were classified into three groups:  1. low-active (<14 MET-hours/week),  2. moderately active (> = 14 MET-hours/week in moderate-intensity physical activity) and  3. vigorously active (> = 14 MET-hours/week including vigorous physical activity) at both phases.  This yielded nine groups for describing stability and change of leisure time physical activity.  Disability retirement data were derived from the registry of the Finnish Centre for Pensions until the end of 2013.  A Cox regression analysis was used to calculate hazard ratios (HR) and their 95 % confidence intervals (CI) adjusting for covariates.


 RESULTS
 During the follow-up, 264 (6.7 %) participants retired due to disability.  Compared with those who were persistently low-active, those who increased their physical activity from low to vigorous had a lower risk of subsequent disability retirement (HR = 0.38, 95 % CI = 0.15-0.97) when adjusting for age, gender, occupational social class, strenuousness of work, smoking and binge drinking.  Similarly, compared with those who were persistently moderately active, those increasing from moderate to vigorous (HR = 0.50, 95 % CI = 0.28-0.86) had a reduced risk.  In contrast, those decreasing their physical activity from vigorous to low (HR = 2.42, 95 % CI = 1.32-4.41) or moderate (HR = 1.70, 95 % CI = 1.03-2.82) had an increased risk, compared with those who were persistently vigorously active.  Adjusting for BMI, limiting longstanding illness and prior sickness absence somewhat attenuated the associations.


 Adopting vigorous physical activity was associated with a reduced risk of disability retirement.  Promoting vigorous physical activity among midlife employees may help prevent disability retirement.
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Adopting vigorous physical activity was associated with a reduced risk of disability retirement. 
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