a) LDL cholesterol is a type of cholesterol which increases the risk of heart disease - Edexcel - GCSE Biology Combined Science - Question 5 - 2019 - Paper 1

The graph indicates that the LDL cholesterol levels in the blood decreased after the man started taking statins at the beginning of February. Initially, in January, the cholesterol level was around 3.5 mmol per dm³. As he began taking the medication, there was a steady decline in cholesterol levels until approximately April, where it reached its lowest point of around 1.0 mmol per dm³.

After discontinuing the statins four months later, the cholesterol levels began to rise again, reaching about 3.2 mmol per dm³ by July. This suggests that statins effectively lower LDL cholesterol levels while they are being taken, but once stopped, the levels can increase again, indicating the importance of continuous medication in managing cholesterol levels.