Contemporary study (option): Hoefelmann et al. (2006)

Aim and sample

Aim: to see whether lifestyle factors are associated with sleep quality and sleep duration in high school students.

Sample: students aged 14 to 24 in Brazil, from a randomised controlled trial promoting healthy behaviour. 2,000 students were randomly selected from 20 schools; 989 completed both assessments.

Procedure

• A closed-answer questionnaire, based on the PACE+ questionnaire, completed twice, nine months apart.
• Sleep quality: 'How often do you think you sleep well?' (always/almost always = positive).
• Sleep duration: 'How many hours, on average, do you sleep per day?' (8 or more = enough).
• Lifestyle: exercise days, strength exercise, TV and computer game time, snacks and soft drinks per week, alcohol days per month.
• Analysed cross-sectionally (at one time) and prospectively (does behaviour at time 1 predict sleep at time 2?).

Results

• About 5 in 10 reported poor sleep quality and 8 in 10 insufficient sleep (76.7% under 8 hours in the cross-sectional data); this stayed the same over nine months.
• Cross-sectionally, some behaviours were associated with sleep (for example frequent snacks and soft drinks with poorer sleep quality and less sleep), but after adjusting for confounding variables no behaviour was associated with amount of sleep.
• Prospectively, none of the behaviours predicted sleep quality or duration.

Conclusions and evaluation

Conclusions: poor sleep perceptions were stable over time; associations found at one time point were not confirmed prospectively.

Evaluation:

• Strengths: large, randomly selected sample; longitudinal (prospective) design; standardised closed questions are easy to analyse and replicate.
• Weaknesses: self-report may be inaccurate or affected by social desirability; about half the original sample dropped out; Brazilian students may not generalise to other cultures; correlational, so no cause and effect.

Worked example

2,000 students were selected and 989 completed both assessments. What percentage completed?

1. 989 / 2000 x 100.
2. = 49.45%.

Answer: 49.45% completed (about half dropped out).

Check yourself

1. In which country did Hoefelmann et al. carry out their study?
   • Canada
   • Japan
   • Brazil
   • Germany
   Show answer

   Brazil. Students were Brazilian.

2. How many months apart were the two questionnaires?
   Show answer

   9 months. Nine months apart.

3. 2,000 students were selected and 989 completed both assessments. What percentage completed, to 2 decimal places?
   Show answer

   49.45 %. 989 / 2000 x 100 = 49.45%.

4. How was 'enough' sleep defined?
   • 6 or more hours
   • 8 or more hours a day
   • 10 or more hours
   • Waking without an alarm
   Show answer

   8 or more hours a day. 8 hours or more was enough.

5. In the cross-sectional data 76.7% slept under 8 hours. What percentage slept 8 hours or more?
   Show answer

   23.3 %. 100 - 76.7 = 23.3%.

6. What did the prospective analysis find?
   • Video games predicted all sleep problems
   • No lifestyle behaviour predicted later sleep quality or duration
   • Exercise doubled sleep time
   • Alcohol improved sleep quality
   Show answer

   No lifestyle behaviour predicted later sleep quality or duration. No behaviour predicted later sleep.

7. Explain one weakness of using a questionnaire in Hoefelmann et al.
   Show answer

   Students self-reported their sleep and behaviour, so answers may be inaccurate because of poor memory or social desirability bias, which lowers validity.. Think about self-report.

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Sources

• Pearson Edexcel International Advanced Subsidiary/Advanced Level in Psychology specification, Issue 5 (February 2021)
• Pearson IAL Psychology component guide: WPS02 (Issue 2, November 2024)
• Pearson IAL Psychology summary of studies: WPS02

Last updated 8 November 2026. Spotted a mistake? Tell us.