Intensity of Physical Activity and Obesity in an Irish cohort using GENEActiv accelerometers

Estimates of physical activity (PA) levels are typically derived from self-report questionnaires which are subject to response bias and recall bias. This study utilizes accelerometers, which objectively measure movement intensity and are not subject to the biases of self-report questionnaires. Rising obesity rates is now a major public health problem for Ireland. PURPOSE: To determine PA levels among a sample of middle aged Irish adults and to explore the association between intensity of physical activity and risk of obesity. METHODS: Data are from a subsample (n=464) ofthe Mitchelstown cohort; a population based sample of 2047 middle aged Irish adults. PA was measured over the course of seven days using the GENEActiv accelerometer. Only respondents who wore the monitor on their wrists and who returned the accelerometer with seven valid (10 or more hours of wear time) days of data were included in the analysis. PA levels were based on published cut-offs¹ and non-wear time was determined using an appropriate algorithm2. Logistic regression was utilised to explore the association between intensity of PA levels and obesity (BMI≥30) adjusting for sex, age, smoking status, dietary quality-score (1-5), education, hypertension and wear-time. RESULTS: Valid data were available on 397 respondents aged 48-72 years. The majority of wear time- 54% for men and 53% for women- are sedentary. Total average daily moderate-to-vigorous-physical-activity (MVPA) was 327 minutes (5.5 hours) for men and 315 minutes (5.3 hours) for women. At ages 50 to 59, both men and women accumulated approximately 30 minutes more MVPA than at ages 60-69. Of respondents 32% were obese. On average obese people were found to accumulate one hour less daily MVPA than non-obese (BMI<30) persons (p<0.001), after adjusting for sex. In a fully adjusted model an association was found between quartiles of daily minutes of MVPA and obesity (overall p=0.01). Those in the lowest quartile had an OR=3.97 (95% CI, 1.65-9.55) (p=0.002) compared to those in the highest quartile. CONCLUSION: The findings indicate that the majority of adults’ wear-time is sedentary and that people with obesity on average accumulate less MVPA per day compared to people without obesity. The study highlights the need to promote PA and to achieve a healthy weight status.