Perhaps you should try some spelling variations:
decrease their » decrease the (Expand search), increase their (Expand search), decreases the (Expand search)
their decrease » the decrease (Expand search), their disease (Expand search), the decreased (Expand search)
decreased risk » increased risk (Expand search), decreased in (Expand search)
decrease hiv » decreased high (Expand search), decrease with (Expand search), decrease of (Expand search)
hiv decrease » via decrease (Expand search), hiv increase (Expand search), will decrease (Expand search)
in decreased » is decreased (Expand search), in deceased (Expand search), and decreased (Expand search)
risk object » disk object (Expand search), mask object (Expand search), task object (Expand search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "(( decrease hiv decrease their decrease ) OR ( decrease in decreased risk object ))~".
• Adding a wildcard symbol may retrieve word variants: (( decrease hiv decrease their decrease ) OR ( decrease in decreased risk object ))*.