All norms are based on data obtained from large samples of participants from specific populations. The scientist or researcher takes the average value from this data and this figure becomes renowned as the norm. When applied to sleep this means that many people would quote that you need 8 hours of sleep each night. Whilst this may be the average of a large sample there will be many outliers - those who fall well below or well above the average. The word normal comes from this word 'norm' and can be particularly unhelpful, as what is normal after all? Hence, the norms described in our blogs are gentle guidelines rather than a prescription for every individual.
Sleep research can be influenced by many factors including:
1. Research location - sleep cycles are inextricably linked to circadian rhythms which differ at various latitudes. Each location will have its own weather pattern, culture, sleep norms and diet - all of which can influence how participants sleep.
2. The season during which the research is made - The darker winter months bring with them an increased desire to sleep as melatonin is switched on earlier in the evenings as the sun sets. In the summer months waking is made far easier by the morning light. Sleep norms change depending on the season!
3. Participants age - it is well recorded how sleep differs through the life stages. Comparing participants of different ages may give a skewed result.
4. Pre-morbid medical conditions - participants with existing sleep disorders will have different sleep norms than participants with healthy sleep lives. Sleep deprivation, naps and length of sleep may effect these two groups very differently as their very neurological wiring may differ to start.
5. Who is funding the research - big corporates have a lot to gain financially by proving that their product improves sleep. Sleep research that is funded by pharmaceutical companies will probably promote a drug of some sorts; whilst sleep research funded by the dairy industry will probably promote a glass of warm milk to end all sleep woes. The best research is conducted by independent Sleep Laboratories or Research Labs where most of these factors can be well controlled and give us valid findings.