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Omega‐3 masne kiseline za prevenciju kognitivnog propadanja i demencije

Background

Evidence from observational studies suggests that diets high in omega‐3 long‐chain polyunsaturated fatty acids (PUFA) may protect people from cognitive decline and dementia. The strength of this potential protective effect has recently been tested in randomised controlled trials.

Objectives

To assess the effects of omega‐3 PUFA supplementation for the prevention of dementia and cognitive decline in cognitively healthy older people.

Search methods

We searched ALOIS ‐ the Cochrane Dementia and Cognitive Improvement Group’s Specialized Register on 6 April 2012 using the terms: "omega 3", PUFA, "fatty acids", "fatty acid", fish, linseed, eicosapentaenoic, docosahexaenoic.

Selection criteria

Randomised controlled trials of an omega‐3 PUFA intervention which was provided for a minimum of six months to participants aged 60 years and over who were free from dementia or cognitive impairment at the beginning of the study. Two review authors independently assessed all trials.

Data collection and analysis

The review authors sought and extracted data on incident dementia, cognitive function, safety and adherence, either from published reports or by contacting the investigators for original data. Data were extracted by two review authors. We calculated mean difference (MD) or standardised mean differences (SMD) and 95% confidence intervals (CI) on an intention‐to‐treat basis, and summarised narratively information on safety and adherence.

Main results

Information on cognitive function at the start of a study was available on 4080 participants randomised in three trials. Cognitive function data were available on 3536 participants at final follow‐up.

In two studies participants received gel capsules containing either omega‐3 PUFA (the intervention) or olive or sunflower oil (placebo) for six or 24 months. In one study, participants received margarine spread for 40 months; the margarine for the intervention group contained omega‐3 PUFA. Two studies had cognitive health as their primary outcome; one study of cardiovascular disease included cognitive health as an additional outcome.

None of the studies examined the effect of omega‐3 PUFA on incident dementia. In two studies involving 3221 participants there was no difference between the omega‐3 and placebo group in mini‐mental state examination score at final follow‐up (following 24 or 40 months of intervention); MD ‐0.07 (95% CI ‐0.25 to 0.10). In two studies involving 1043 participants, other tests of cognitive function such as word learning, digit span and verbal fluency showed no beneficial effect of omega‐3 PUFA supplementation. Participants in both the intervention and control groups experienced either small or no cognitive declines during the studies.

The main reported side‐effect of omega‐3 PUFA supplementation was mild gastrointestinal problems. Overall, minor adverse events were reported by fewer than 15% of participants, and reports were balanced between intervention groups. Adherence to the intervention was on average over 90% among people who completed the trials. All three studies included in this review are of high methodological quality.

Authors' conclusions

Direct evidence on the effect of omega‐3 PUFA on incident dementia is lacking. The available trials showed no benefit of omega‐3 PUFA supplementation on cognitive function in cognitively healthy older people. Omega‐3 PUFA supplementation is generally well tolerated with the most commonly reported side‐effect being mild gastrointestinal problems.

Further studies of longer duration are required. Longer‐term studies may identify greater change in cognitive function in study participants which may enhance the ability to detect the possible effects of omega‐3 PUFA supplementation in preventing cognitive decline in older people.

PICO

Population
Intervention
Comparison
Outcome

El uso y la enseñanza del modelo PICO están muy extendidos en el ámbito de la atención sanitaria basada en la evidencia para formular preguntas y estrategias de búsqueda y para caracterizar estudios o metanálisis clínicos. PICO son las siglas en inglés de cuatro posibles componentes de una pregunta de investigación: paciente, población o problema; intervención; comparación; desenlace (outcome).

Para saber más sobre el uso del modelo PICO, puede consultar el Manual Cochrane.

Plain language summary

Riblje ulje za prevenciju demencije kod starijih ljudi

Demencija je progresivna bolest koja pogađa uglavnom starije osobe. Prethodna istraživanja u obzervacijskim studijama pokazala su da povećana konzumacija ribljeg ulja koje obiluje omega‐3 polinezasićenim masnim kiselinama može smanjiti vjerojatnost razvoja demencije, dok su druge studije pokazale da tog učinka nema Ribe kao što su losos, skuša, haringa i sardine bogat su izvor ribljeg ulja i omega‐3 masnih kiselina, koje su nužne za razvoj mozga.

Cochrane sustavni pregled uključio je studije u kojima su sudjelovali zdravi ispitanici stariji od 60 godina koji su na početku studije bili kognitivno zdravi, i koji su u studiji bili nasumično raspoređeni u skupinu koja je primala omega‐3 masne kiseline u prehrani ili placebo (kao što je maslinovo ulje). Glavni ishodi koji su promatrani u sustavnom pregledu bili su novi slučajevi demencije dijagnosticirane tijekom razdoblja trajanja studije, kognitivnog propadanje, nuspojave i pridržavanje propisanoj intervenciji.

Autori su u sustavni pregled uključili 3 randomizirana kontrolirana pokusa s ukupno 3536 ispitanika. U dvije studije ispitanici su bili nasumično raspoređeni u skupinu koja je primala gel kapusle koje su sadržavale omega‐2 masne kiseline ili maslinovo ulje ili suncokretovo ulje tijekom 6 ili 24 mjeseca. U trećoj studiji su ispitanici nasumično raspoređeni u skupinu koja je dobila margarin kao namaz obogaćen omega‐3 masnim kiselinama ili skupinu koja je dobila obični margarin.

Nijedna od analiziranih studija nije istražila učinak omega‐3 masnih kiselina na nove slučajeve demencije tijekom razdoblja ispitivanja. U dvije studije koje su uključile 3221 ispitanika nije bilo razlike između omega‐3 masnih kiselina i placeba u rezultatima ispitivanja mentalnog statusa na zadnjem pregledu. U dvjema studijama (1043 ispitanika) drugi testovi kognitivne funkcije nisu pokazali koristan učinak nadomjestaka omega‐3 masnih kiselina. Ispitanici u objema skupinama – intervencijskim i kontrolnim – opisali su malo ili nimalo kognitivnog propadanja tijekom istraživanja.

Glavne opisane nuspojave omega‐3 masnih kiselina bile su blage probavne tegobe, ali je ukupno blaže simptome opisalo manje od 15% ispitanika te su ispitanici u kontrolnoj skupini imali jednaku vjerojatnost pojave nuspojava kao i oni koji su primali nadomjestke omega‐3 masnih kiselina. Pridržavanje propisanoj intervenciji bilo je visoko u svim studijama i ispitanici su konzumirali prosječno 90% nadomjestaka. Sve tri studije imale su visoku metodološku kvalitetu pa je stoga malo vjerojatno da se opisani rezultati mogu pripisati slučajnosti ili pristranosti.

Rezultati dostupnih studija pokazuju da omega‐3 masne kiseline nemaju blagotvoran učinak na kognitivnu funkciju među kognitivno zdravim starijim osobama. Omega‐3 masne kiseline možda imaju druge blagotvorne učinke na zdravlje i autori preporučuju konzumaciju ribe kao dio zdrave prehrane.

Da bi se utvrdio eventualni učinak omega‐3 masnih kiselina na prevenciju kognitivnog propadanja potrebne su dulje studije tijekom kojih bi se mogle očekivati veće promjene u kognitivnoj funkciji.