* Sees 5 pct decline in 2009 adj EBITDA

* Q4 adj EBITDA at 1.36 bln euros, matching consensus

* Quarterly sales slide 1.5 percent

* To 'wait and see' on further cost cuts

(Adds more details, shares, analyst comment)

LEVERKUSEN, Germany, - Bayer cut its 2009 outlook for underlying operating profit to a decline of 5 percent, having previously foreseen an increase, as a slump in demand for its plastics and foams overshadowed growth at its drugs unit.

For our MaterialScience business ... we anticipate a very difficult year marked by a great deal of uncertainty, Chief Executive Werner Wenning said in a statement on Tuesday.

Fourth-quarter earnings before interest, tax, depreciation and amortisation (EBITDA) before special items, or underlying operating profit, slipped 4.6 percent to 1.36 billion euros ($1.71 billion), in line with the average estimate in a Reuters poll of 15 analysts. [ID:nLP230762] Quarterly sales edged 1.5 percent lower to 7.92 billion euros, surpassing the 7.83 billion euro average estimate.

Bayer scrapped a previous outlook for group sales to rise in 2009, with the company now forecasting 32 billion euros, down from the 32.9 billion posted last year.

Bayer, which derives about 70 percent of sales from its less cyclical healthcare and pesticides businesses, has so far fared better than fellow chemicals-to-drugs hybrids Solvay and Merck KGaA.

Belgium's Solvay posted disappointing fourth-quarter operating profit and said it was bracing for two difficult years ahead. Merck missed its profit targets and declined to give a forecast for 2009.

Adjusted EBITDA at Bayer's MaterialScience unit, the world's largest maker of padding and insulation foams and of plastics used in sports goggles and car lights, slumped 85 percent to 54 million euros in the fourth quarter, capping a year of quarterly earnings declines.

Unlike plastics peer BASF, which last week said it would cut 1,500 jobs, Bayer stopped short of taking measures that go beyond the already announced cuts in working hours and pay.

We will now wait and see how things develop - particularly at MaterialScience - before we decide on any further measures, Wenning said.

BASF competes with Bayer in the market for padding and insulation foams among others, but does not sell drugs.

Bayer shares slipped 2.5 percent to 35.80 euros by 0834 GMT, while the DJ Stoxx European healthcare sector index advanced 1.2 pct.

The first impression certainly leads to a negative sentiment, said Frankfurt-based Kepler Equities analyst Daniel Daetwyler.

But the business model, with a focus on healthcare, is working despite the difficult environment. If you compare it with other companies that gave no outlook for 2009 at all, there is a degree of assurance, he added.

According to Thomson Reuters StarMine, which weights analysts' forecasts by their track record, shares in Bayer trade at about 10 times estimated 12-month forward earnings.

The multiple puts it in line with global healthcare peers as Bayer's relative safety from generic-drug competition is tempered by concern about the downturn at its chemicals division. ($1=.7924 Euro)

(Reporting by Ludwig Burger; Editing by Jon Loades-Carter)