| Date | May 2013 | Marks available | 2 | Reference code | 13M.3.SL.TZ1.1 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Compare | Question number | 1 | Adapted from | N/A |
Question
Elderly people lose bone mineral density (BMD) with age, and this is the source of many health issues, including higher risk of bone fractures. Researchers measured the change in BMD amongst elderly men considering many factors, over a period of four years. The results presented below show the difference between bone density change due solely to vitamin C intake and bone density loss considering a combination of the other factors represented by the baseline (zero). BMD was measured in the spine and at two femur (thigh bone) locations (femoral neck and trochanter) using scanner images. Daily intake of total vitamin C was categorized as high, medium or low.
Outline the effect of vitamin C intake on changes in bone density in the spine.
Compare the changes in bone density of the femoral neck with those of the spine.
Evaluate the evidence provided by the data that the intake of vitamin C supplements may reduce bone density loss in elderly people.
Markscheme
a. high (vitamin C) causes a positive change (in BMD) whereas medium/low causes negative change;
b. inversely proportional (for relative change);
c. if vitamin C intake increases, BMD increases;
a. positive change/reduced loss for femoral neck at all levels whereas only at high intake for spine;
b. higher values for femoral neck for each intake category;
c. inversely proportional for both;
d. no overlap between range/standard deviation / clear distinction of protective effect between femoral neck and spine (for high/all intake categories);
Implications:
a. high intake results in positive value (for all locations);
b. protective effect proportional to intake;
Limitations:
c. proportion of vitamin C intake from supplements / influence of other factors not stated;
d. only a few bone locations measured / sample size unknown / high medium and low not defined;
At least one implication and one limitation required.
Examiners report
The data in A1 was understood by most candidates who were able to analyse the data and connect the vitamin C intake to changes in bone density.
Many students failed to compare the data and only achieved one mark.
Few candidates evaluated the evidence provided. Practice of this style of question is invaluable in preparing for the examination.
