International Journal of Preventive Medicine (Int J Prev Med)2008-780233(S)20120310536536EN20120310<p><strong>Background:</strong> Mental disorders such as depression, anxiety and dementia are common in elderly. However, physical activity is suggested to be effective in preventing such aging-related disorders. The aim of this study was to investigate the role of physical activity on mental health in later life.<strong> </strong></p><p><strong>Methods</strong><strong>: </strong>Four hundred elderly people were randomly divided into the intervention and control groups. The intervention consisted of exercise twice a week for two months. Mental health status before, just after, and three months after the study was assessed with the 28-item General Health Questionnaire (GHQ-28(.</p><p><strong>Results</strong><strong>:</strong> The mean of the GHQ-28 total scale decreased in the case group and this change remained significant after three months (before: 8 &plusmn; 5.5, after three months: 5.6 &plusmn; 4.6, p &lt; .001).<strong> </strong>GHQ subscales including somatization, anxiety, social dysfunction, and depression decreased significantly in the case group just after and three months after the intervention.</p><p><strong>Conclusion:</strong> Physical activity significantly prevents mental disorder in older adults. Although it has effects on anxiety, social dysfunction, and depression, the greatest influence is on improving the somatization symptoms.</p><strong>Keywords:</strong> Aging, GHQ-28, mental health, physical activityhttp://ijpm.mui.ac.ir/index.php/ijpm/article/view/536http://ijpm.mui.ac.ir/index.php/ijpm/article/download/536/417